12Volt Devices
There are so many new 12Volt appliances and devices that are regularly added to our range of choices that it’s hard to keep up sometimes. This list will therefore remain a moving feast, and I’ll update it as new 12Volt stuff becomes available.
The current draw (in Amps) of 12Volt devices will typically be either on the equipment label itself or somewhere in the specifications part of the manual. Sometimes the power draw (in Watts) will be shown instead, and in that case just divide the Watts by 12 Volts, and that’ll give you the current in Amps.
So why do we care how much our 12Volt equipment uses?
Total Daily Energy Usage
I’ve put this bit upfront, as it’s the single most important figure we can use for working out the size of a 12Volt system. It’s also the starting point for the articles on How much Solar? and How much Battery?
It’s the solar’s job to put back what I’ve taken out of my batteries, and it’s the battery’s job to store the solar energy so I can use it any time, day or night. So to be able to work out how much solar and battery capacity I’ll need, I first have to work out how much energy I will use. Let’s look at a simple example.
Example
For 12Volt camping and caravan systems I prefer to work in Amps and Amp-hours, and to then work out what a typical day’s usage looks like. We will also use this later to calculate our battery and solar sizes. So let’s say we have a simple case of:
- a 40-litre camping fridge
- a 12 Volt TV
- a strip of LED lights
Using the table below, we can see that the fridge will be the main culprit, at about 35Ah/day for average use. However for our solar input we are going to use the worst-case of winter-hours, and to match that we are going to use 25Ah/day for the fridge. That way both the solar and the fridge have figures which reflects winter conditions. (see heading below on Fridges).
Then if we use the TV for 5 hours, this will add another (5hrs x 3Amps) = 15Ah/day. And if our LED strip-lights are used for 5 hours a day, then that’s (5hrs x 1Amp) = 5Ah/day.
So in this example over a typical 24-hour day we will be using 25+15+5 = 45Ah/day. We will use this figure of 45Ah a day as an example for both How much Solar? and How much Battery?
Tailoring the Total Daily Usage
This daily figure can be tailored to suit our individual needs by modifying the figures to suit, and by adding other 12Volt devices to the total. For instance if I only use my TV for 2 hours instead of 5 hours as in the table, then the TV’s contribution will now be (2hrs x 3Amps) = 6Ah a day. In this case I will be saving myself 9Ah every day, compared to the 15Ah in the table.
List of 12Volt Devices
The following headings are in alphabetical order, and each device and its typical current draw is discussed, and then summarised in a table at the end. There are always variations to these “typical” figures, so the discussion is to help us tailor them to our particular situation – and for fridges the discussion gets a bit longer as their energy usage tends to vary quite a bit. From the table it’s also easy to see why we pay special attention to 12Volt compressor fridges – they use the most power.
CPAP Machines
Most of the newer models will either work directly off 12Volt or they have a 12Volt adaptor that will plug into a cigarette socket. They will work fine off an inverter but the downside with that is that the power losses, which means we may not get a full 8 hours out of our 12Volt battery, so it’s best to avoid an inverter if possible. It’s not easy to get actual power consumption data on these machines – mostly you’ll get maximum power or current being specified. One thing that is consistent throughout the various makes and models is that turning the humidifier off reduces the current draw to a half or even less. After some considerable trawling through the various makes and models it appears the best guesstimate for CPAP machines is a daily draw of 15 to 30 Amp-hours. This assumes an expected use of 8 hours a day and that the humidifier is off.
Update: It seems there are also some very efficient ones out there – just 6Ah for a good night’s sleep! Take a look at the info in Hilto’s comment below – might be worth doing some research…
Electric Blankets
Now this is one way to keep things warm efficiently, and because 12Volt systems are limited in the power they can provide, this is a great option. So you’d think that most retailers and online shops would carry them, right? – yeah, so would I, but turns out we’d be wrong. Apart from the eBay stores which can be a bit of a Russian-roulette at times, I can only find one Australian-based store that sells 12Volt electric blankets, and they’re a bit pricey too. But when it comes to something I’m sleeping with (so to speak) I want to be as safe as possible, so I’d rather pay for that peace-of-mind[1]. Typical current draws vary from about 3 to 6 Amps, so using the 3Amp model as a pre-warm blanket for 2 hours a night will use just 6Ah (2hrs x 3A = 6Ah). Leaving it on a lower setting during the night is also possible with some models.
Running a 240V electric blanket through an inverter is an option, but not a good one. Firstly I’m not that keen on having my bed wired to 240V – at home I switch off the electric blanket before I get into bed. And secondly, introducing an inverter just increases our losses – the very thing we were trying to avoid!
So for myself I’d rather stick with the more efficient and safer 12Volt versions, but now that you know the ifs and buts, over to you.
Fans
12Volt fans that have been designed in the last 5 years or so will be using the very efficient and quiet brushless DC motors. These fans move a good amount of air and are the only practical alternative to a 240Volt air-conditioner[2]. They come at a bit of a price but there are well-established brands out there, and they are stocked by most good retailers. Their current draw is below half an Amp at 12Volts so even leaving it on for 8 hours will only take 4Ah from our battery (8hrs x 0.5A = 4Ah). The better ones also have a timer which can be set to turn the fan off automatically after a certain time.
Fridges
Here we are talking 12Volt compressor fridges, and this is one of the most tricky items to pin down in terms of power draw. But because it’s also the biggest power draw in most 12Volt systems it’s really important that we get this one right. (The article on Fridges has more info on non-compressor fridges that run on gas and the little cooler/warmers).
Manufacturers of fridges tend to use test conditions that will show their products in the best possible light. So tests with fridge temperatures of 5°C and ambient temperatures under 30°C are quite common. These are however very seldom the temperatures us average campers come across – unless you like warm beer and travel only in mid-spring and mid-autumn. The tests also don’t specify how often the fridge is opened and closed – maybe they just keep it closed while testing to minimise current draw – who knows?
Tests on Chest Fridges
Anyway, the figures in the table here are based on actual tests I did of typical 12Volt camping fridges available in Australia. We used both the Engel range and Waeco-CFX range of fridges side-by-side. They were tested over a number of months, including summer conditions with ambient temperatures above 35°C, and the interior temperature setting was -5°C[3]. We ran two types of tests – fridges left closed, and fridges loaded every 24 hours with up to 12 litres of room-temperature water – this gave us a whole range of power consumption figures which mimic the way in which us campers typically use fridges in real life.
Of course the figures aren’t perfect – no test ever is, and everyone’s situation will differ – but it does give us a set of real-world figures to work from. And by-the-way, in terms of power consumption there was very little difference between the two brands – some won some days, others won other times, but on average they were surprisingly consistent.
When we loaded the fridges up with a full 12-litres of room-temperature water, as you’d expect the consumption went up. Also, over long weekends the fridges would be left to themselves, and by the second day the energy usage came way down. These are the Low and High figures in the table. So if you’re freezing your summer catch each day, then expect the higher figure. If you’re camping in the cooler months and just want the milk & veges to stay fresh, the lower figure will be more likely.
There are a number of brands out there, and except for the Engel, they tend to use the Secop (Danfoss) compressor, so from that angle their usage will all be quite similar. The other big factor that affects fridge efficiency is the insulation. Better insulation means we lose less to the outside atmosphere, so we use less energy. For instance if you compare a household 240V fridge to a 12Volt camping fridge, the difference in insulation thickness is pretty easy to see. The same is true if you compare Waeco’s CF and CFX range – the CFX has much thicker insulation, and the CF-range therefore uses a good one-third more energy than the figures in the table. Also, National Luna fridges inject their insulation at high pressure so it’s very dense, so it takes up less room and is very efficient at keeping the inside cool.
Upright Compressor Fridges (12 Volt)
Upright compressor fridges are typically 80 litres and up, all the way to 220 litres and the bigger ones usually have a separate freezer door. Engel also make an 80 litre freezer-only with a slightly bigger compressor, which can be paired side-by-side with their 80 litre fridge-only option.
Uprights obviously use more energy than the same size chest-type, especially if the door is opened often, but uprights are much more convenient in caravans and can be built-in. In terms of energy usage most uprights use the big BD-50 12Volt compressor, so their consumption then depends on the amount of fridge-gas used, which increases with fridge size. For a 110 litre upright we can expect to use about 90Ah a day at 12Volt, and for the bigger sizes this can go to 125Ah a day and upwards, especially if it’s working hard.
Fridges and Solar – a balanced setup
With all 12Volt compressor fridges, if we are using solar to replenish our batteries, then we have a bit of Mother Nature on our side too. In summer the fridge is working harder, but we also have more solar power available. Same thing in winter – we have less sun but the fridge has a pretty easy time keeping things cool, so all round we have a nicely balanced system.
Inverters
The power that an inverter will use from the 12Volt system is determined by the power of the 240V equipment we have connected. In the article on Inverters we devised a quick-and-easy formula to calculate the current on the 12Volt side of things – we simply divide the power by 10, so knock off a zero. So if we have a laptop running on 240V through an inverter, and its power-supply is rated at 80 Watts, then we will be drawing about 8 Amps from the 12Volt system. So a 5 hour session on the laptop will draw 40Ah from our battery (5hrs x 8A = 40Ah) – quite a considerable amount. There is an article on Inverters which gives more detail on these hungry little beasties, and the short version is that inverter use is best kept to a minimum.
Kettles
Anything that has to do with heating is always a bit of a challenge for 12Volt stuff – we don’t have much voltage so to get the power up (Watts) we have to increase the Amps (Watts = Volts x Amps). And then the issue is that above 15Amps or so we start to stretch our friendship with a few things – plugs, cables, sockets, and also our batteries.
Waeco makes a very good 12Volt kettle that stretches most of these parameters a bit, but it still works pretty well considering what it’s up against. The compromise is that it takes 3 cups (750ml) and takes about half-an-hour to boil. So if you were hoping for a quick cuppa while you park beside the road, then it’s probably worth sticking to the gas. On the other hand I find that in the morning, if I hit the on-button when I wake up, by the time I’ve washed my face and worked out which way’s up, the kettle is boiling happily for our morning cuppa. Anyway, it’s another 12Volt option that’s out there, and it draws about 15 Amps for ½ hr so its energy usage is about 7.5Ah to boil a full kettle of 3 cups.
Lighting
Many years ago I was impressed by some funny-looking diodes that emitted a red glow if you passed a current through them. The moment I saw them I knew this was the future of lighting. The old incandescent bulbs produced 98% heat and just 2% useful light. This made them an easy target to beat, but they remained the best option for over a hundred years. Halogen bulbs were a lot better but were very soon superseded by LED lighting. Fluorescent tubes remain as efficient as LED, and in some applications they are still the best option when coupled to an efficient 12Volt ballast.
But LED lighting has completely transformed the interior and exterior lighting for camping and caravanning of all shapes and sizes, and is now far-and-away the most used technology for 12Volt systems. LEDs use about one-fifth of the power compared to an incandescent (glow-worm) bulb. It’s therefore tempting to disregard any power-draw from LED lighting as “one-tenth of buggerall” – but this is often not true. For instance a flexible 1.2 metre-long LED strip-light draws close to 1.5 Amps, and over an evening’s use of 5 hours or so, this one light will set our battery back by 7.5Ah (5hrs x 1.5A = 7.5Ah). Now even with a smallish 100Ah battery this is not too much, but if there are a number of other lights running at the same time, then things can start to add up, even if they are LED.
LED Replacement Globes
If you have light fittings with the older 12Volt Halogen bulbs in them, these can easily be replaced with LED-bulbs which usually provide a better light and definitely draw less current too. These LED-replacement globes come in all shapes and sizes so before heading off to your local retailer, maybe take a picture or make a careful note of how the bulb goes into the fitting – from the side, from the back – and also the space available for the replacement bulb. Better still, if you can take the whole light-fitting with you then you’ll be able to go through the options to find one that suits best.
Microwave Ovens
In the post on Inverters we talk about Microwave ovens, and worked out a current draw of 110Amps at 12Volt for a 850W microwave. If that ran for just 5 minutes, that would take 9.2Ah out of our batteries (5min/60 x 110A = 9.2Ah), so 50% more energy than our 12Volt oven below. More importantly, the 12Volt oven’s 6Amps is no problem for our deep-cycle batteries, but 110Amps – whoa, rather not on my batteries thanks!
Ovens
Yes, 12Volt ovens – if you’ve not yet come across the Australian-made Travel Buddy oven, then have a look around – and talk to the guys on the road – they’ll tell ya! It draws about 6 Amps when it’s going and has a timer which switches the oven off so it won’t keep flattening your battery. Cooking times vary depending if the food is thawed or frozen, but 60-90 minutes is typical. So if we use the oven for one hour a day that will consume just 6Ah from our battery (1hr x 6A = 6Ah).
Pumps – Water
The most common water-pump used in camper-trailers, caravans, motorhomes and so on, is the Shurflo 4009 12Volt pressure pump. It operates on a pressure-switch which turns it off when the tap is closed. These pumps draw about 5 Amps, and the time they run is usually pretty short, given we have to carry our water with us when we free-camp. The pumps can deliver about 10 litres/minute so it will happily drain a 100 litre tank, from full to empty in just 10 minutes – yikes! So even if we go overboard and say we’ll have the pump on for 5 minutes a day, that will consume less than half an Amp-hour – very, very little is the short answer (5min/60 x 5A = 0.42 Ah). Also, having the tap half-open will help reduce the water usage but won’t affect the current draw that much.
Transfer Pumps – Water & Diesel
There are also so-called transfer pumps, which are usually submersible 12Volt pumps with a set of power leads so it can run off a 12Volt battery. These pumps can be used to transfer either diesel from a jerry-can into a fuel tank, or to pump water from a creek into the caravan’s tank, and so on. Typically they are not self-priming, so they can’t suck up liquid in a pipe, but once they have liquid in them they can shove that liquid many metres high at rates from 15 to 30 litres a minute. So a 20-litre jerry-can will be done in a minute or two. They also draw around 5 Amps at 12Volts and because of the very short run-times power usage is usually not an issue.
Bilge Pumps
Ok, on this one, the best I can do is to say that it varies – a lot. Every situation is so different to the next that it is simply not possible to estimate the energy that Bilge Pumps draw from the battery. The only sure-fire way to get a fix on how much the pump is using, is to measure it for your situation.
If you have access to a DC power-meter[4], then you can measure the daily Amp-hours directly and also get an average over a good few days to take into account weather changes, etc.
The measurement could also be as simple as seeing how long it takes to partially flatten a battery – so fully charge a 12Volt battery and let it run for a few days and then see how much it’s taken out of the battery. For instance if a 100Ah battery is connected to run the bilge pump and after 3 days it is down to 70% of its capacity[5] then it has used about 30% of the battery’s capacity. So 30% over 3 days is about 10% of the battery each day, so the pump uses about 10Ah a day (10% of 100Ah = 10Ah).
TV
LED TVs have been around a while now, and the whole of Australia is on digital TV too, so there are now a whole range of TVs that are quite happy to work off 12 Volts. A typical 24-inch TV will take about 3Amps from the 12Volt supply, so if we have that going for about 5 hours a day, that will draw 15Amp-hours from our 12Volt battery (3A x 5hrs = 15Ah). Have a look on the back of the TV or in the manual to see how much your actual model is drawing, as some of the bigger ones can be 5 Amps and beyond.
[1] The Australian supplier’s website has some pretty persuasive pictures showing how things can go wrong. The blankets they supply are both USA-made which is a fairly good indicator of quality.
[2] There are 12/24V air-cons but they draw huge currents – 30 Amps and up.
[3] This is the so-called “ice-cold-beer” temperature, but things at the bottom of the fridge may start to freeze.
[4] Plasmatronics solar regulators can measure the Amp-hours too, by running the pump off the Load terminals (ensure the pump draws less than the Load terminals can handle).
[5] The table at the end of Batteries: their Quirks & Characteristics, compares battery voltage to its remaining capacity
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64 Comments
Thank you so much, great information
No worries Kevin – glad the 12Volt Blog is useful!
Cheers,
Alistair
Hi Alistair,
Thanks for this awesome resource! Just what I was looking for as I work through provisioning my power systems while awaiting delivery of a new vehicle & camper body.
I’m hoping you might be able to shed some light on one issue I’m having trouble understanding. I have a work laptop I want to be able to fire up (albeit as infrequently and for as short a time as possinble) while I’m on some extended travels next year, borders notwithstanding! It’s actually a mid-range gaming laptop I chose for its computing power rather than the gaming functionality. The downside is it has a thumping big brick of a power supply that draws 3.5A at 240V AC, so 840W (though I expect it would only be drawing this much when doing heavy graphics & gaming duty). Now if I understand correctly, a Watt is a Watt is a Watt, no? So why does the power supply output 11.5A @ 20V DC, thus 230W? If the laptop needs 230W why such a big draw on the input side? Sure there’s some losses in the conversion, but???
I’m also thinking that rather than take the double-hit of 12V -> 240v inverter -> power supply -> 20V it’d be better to use a 12VDC -. 20VDC converter straight up, which would also mean I could use a lower-capacity inverter. Or there’s always the Plan B to get a less-powerful laptop just for when I’m on the road… probably work out cheaper than a big inverter too!
Thanks again
Cheers
Ian
Hi Ian,
First off, thanks for the kind words – glad the 12Volt Blog is proving handy!
And then – man, is that some curly question?! Let’s see if we can uncurl this one a bit…
You are 100% with “a Watt is a Watt” but when we do AC there’s a thing called power-factor which mucks things up a bit – I think the best way of explaining it is to say it’s like a sail in a 40km/h wind, but it’s coming from an angle, so you don’t get the full effect of that 40km/h wind. So power-factor would explain some of the AC-DC wattage difference, but 840W vs 230W is huge, so there’s definitely more to it than that. Another factor might be that manufacturers specify the Max (peak) input current at 240V (just for a few seconds), and that could distort the figures too.
Anyway, back to the more sensible DC side of things, and you’re dead right to zero in on this, rather than the up-down conversion from 12V to 240V and back to 20V.
Elsewhere in the 12Volt Blog comments I mention 12Volt Laptop power supplies, and these simply (and efficiently!) up-convert the 12Volt to the 19 or 20V needed by the laptop. An internet search for “12Volt Laptop power” should bring up some options for you – around $100.
Only problem is, the biggest I could find is150W, which leaves you short – BUT – a Laptop power supply has to have enough to run the laptop (at full tilt) plus charge its batteries. I reckon (but you’d need to check it first) there’s a good chance you’d be able run your laptop with a 150W power supply – and even if it flattens its batteries a bit while you’re working, once you close the lid it can recharge its batteries again. It’s a really simple and efficient solution so probably worth checking out.
I reckon source a supplier for the 150W 12V power supply, and then – acid test – go down and try your laptop on it to be 100% that it actually works – sounds like a plan?
Hope this helps.
Cheers,
Alistair
Brass Monkey fridges use an LG Compressor and are excellent for their price point. I have a fridge/freezer one with 2 compartments (50 litre total) and when both run on fridge 2° seem to use about 30Ah a day. When I have fridge 2° and freezer -20° it uses about 90Ah a day as is running nearly all the time switching between cooling the fridge then the freezer side. There is some off time but not a lot when it’s hot.
12V electric blankets. KickAss sell one and I bought it. 3 heat settings and max run time of 45mins each time it’s turned on so you can’t leave it on accidentally all night. If you need longer than 45 mins you just turn it on again straight after.
Cooking in the wind – I have a 300Ah Lithium battery, 3000W inverter and use an induction cooktop ($40 off eBay). Induction heats (water) twice as fast as gas.
12V ovens. I use the KickAss 12V Travel Oven with glass door and interior light. Heats up to 180° and has a timer or can be put in manual mode to just stay on. It’s 130W so ok off a large battery or run it while driving which is better. I’m now also exploring air fryers and the Ninja Foodi Flip is looking like the best solution there.
Hi Jerry,
Thanks so much for adding to the info on the 12Volt Blog.
Some really handy tips and measurements there!
Cheers,
Alistair
Hi Alistair,
This is a brilliant collection of information, this is the closest I’ve come to understanding electricity.
I am having trouble finding information about 12v cook tops. Not sure if it’s a good idea or not, but cooking in the wind is difficult as is cooking at altitude.
Any advice would be lovely!
Pam
Hi Pam,
Glad you’re finding the 12Volt Blog useful – that’s what it’s all about!
As I mention under kettles, 12Volt and cooking are not great friends – heat requires Watts, and lots of it, and because Watts = Volts x Amps, having just 12Volts (compared to 240V) is not a great start…
There are some 12Volt cooking options, but they usually are slow, like the 12Volt Travel Buddy Ovens – but if you have time on your side, then maybe that’s worth a try?
Also, if you have a really big battery, like 200Ah or more, then an induction cooktop is possible (on a 12V-to-240V inverter), but big inverters are pricey, and not very kind to your 12Volt battery either.
Sorry I can’t be more positive but for fast cooking, gas is still about the best – and for the wind there are some nifty folding wind-shields around – might be worth checking them out?
Cheers,
Alistair
Hey there, awesome info.
I am looking at fridge with the below specs.
What I am confused about is how to work out the Ah for the unit.
I know that Ah is current draw per hour x hours of use, but if I am using a straight 12V DC system, this equates to 7.5 x 24hrs = 180Ah? Seems way too high?
Rated Current AC: 1.3A @ 12V | 0.6A @ 24V
Rated Current DC: 7.5A @ 12V | 3.7A @ 24V
Cheers
Hi Anthony,
Apologies for the delay – been away, out of mobile range…
First off – do you know if it’s a compressor fridge? If so, the compressor will cycle on and off to keep a constant temperature inside the fridge, so if it’s on half the time (and off half the time), that means the consumption is only half of the 180Ah = 90Ah. Typically a compressor fridge will be on for about one-third of the time, once it’s got everything down to temperature, and with no-one diving in and out of the fridge. But even so, that still means 180/3 = 60Ah per day, or more if it’s working harder – that would be okay for a fridge of 80 litres or more, but otherwise that’s a bit much.
The AC current ratings don’t make sense to me, and I’m not sure where you’d source 12V or 24V AC while out camping, but maybe there’s something I’m missing…
If it’s not a compressor fridge, then my guess is it’s going to draw that 7.5A all day – in which case I’m 100% with you – that’s way too high.
Hope this helps.
Cheers,
Alistair
This information is fantastic mate. Greatly appreciate all the work you have put in here for all like myself just starting this learning journey.
I came across this article searching for info on 12v fridges and current draw on battery supplies, as i have just bought myself a portable lithium power station, a 25ah iTECH300P 12v and 300w inverter, as a quick and easy option too take away with my 50L brassmonkey fridge freezer just for the quick weekend getaway trips camping in the rooftop just me and my partner.
Now I looked around and found that this particular one sounded the best and easiest for my needs (obviously not the case) as it had great reviews with 12v fridges being run and a video of it being used by a YouTuber on getaways with 12V fridge and plugged into solar because this model has a form of mppt and the capability to charge and discharge at the same time and i happen to have a solar blanket that is in the ute at the go aswell, Perfect right 😄… well this is where I came into the problem.
So after purchase of the battery system… i decided to do a trial run with it before going away this weekend and everytime I plug the fridge into it at the cig socket whether it is pre-cooled already, or on fridge or freezer mode, or both (and yes turned to Echo mode on the fridge aswell), after a time the over current protection is somehow triggered on the battery station and turns shuts off the power to the fridge. This is obviously the worst thing that can happen to a fridge when running and your not paying attention to it every minute. Anyway could you please help me out with why this is happening when both of these devices are 12v and the amp draw of the fridge is 5/2.5 amp. I am stumped and am at a loss here. Itech world could not help me as they are saying its the fridge but there is no reason it would be anywhere I can see on the specs of the fridge itself. Thank you in advance for any help or any light you can shed on this for me. Cheers.
Lez
Hi Lez,
Thanks for the query – it’s a really curly one – so let’s unravel it a bit.
The 12V “car port” outlet on the portable power station can only give you 10 Amps – not sure why it’s limited like that, but this could be an issue (same limitation on their bigger powerpack).
I also looked up the specs for your fridge/freezer and it says 3.75 Amps, so all should be fine, as you said – so we’re basically looking for a snake in the grass somewhere…
Possibility 1: When a compressor starts up there is a quick spike in current – this can be 5 times the running current – so in that case we are well over the limit of the power pack. Sounds like it has an electronic over-current cut-out and these can be really sensitive too. Puzzling though that this doesn’t happen when you first plug the fridge in…
Possibility 2: the internal battery may be less than 12Volt, with some electronic trickery to up-convert it to 12 Volts. It could be that this converter is overheating after running for a while, and shutting down to protect itself.
Either way it sounds like you’ll need to return it – in consumer terms they’ve sold you something that is not “fit for purpose”.
iTechworld probably won’t be happy, but maybe they’d rather have that than a bad review on their website, or have a case against them at Consumer Affairs.
If you do get it returned, I’d probably look at higher Ah for the batterypack – preferably around 100Ah.
Hope this helps!
Cheers,
Alistair
You sir are a legend !!!. Absolute information and real world testing. Could you recommend a good fitout list, mediocre price range, 200Ah lifepo4. dcdc charger. inverter ( pure sine ) 300-350w solar panels. just would like like to know yr picks. thanks again for the priceless blog and info. cheers mate
Hi Doug,
Thanks for the kind words mate – glad you’re finding the 12Volt Blog useful!
Well, I’m going to follow your lead with the 200Ah LiFePo – nice and generous – to fit with that I’ll happily recommend InterVolt as the DC-DC charger – Australian designed and made – not the cheapest, but the best, by far.
Now Latronics make great inverters, very efficient, huge surge capacity – also Australian (some say built like a brick s-house) – and the size will depend on your 240V equipment. Solar panels are a bit more tricky – so many brands out there – look for one that’s not a “cheapie” and have a careful read of the reviews – over-the-top positive reviews are a bit of a give-away… (;-)
Generally if you find a place that stocks Latronics and InterVolt, they’ll stock other good products as well.
Hope this helps mate.
Cheers,
Alistair
Hey there! when you say you don’t like to have your bed connected to 240v, where is the 12v electric blanket directly connected to?
Hi Kade,
Good question! The 12 Volt electric blanket is connected to the 12Volt supply, but because it’s low voltage you won’t get a shock from it if something goes wrong. (e.g. putting your hands on 12V terminals won’t even give you a tingle, but don’t try that on 240V – please!).
(;-)
Even so, it’s best to use an electric blanket (even 12V) as a pre-warmer only.
Cheers,
Alistair
After reading this anyone can understand the basics of 12-volt camping gear. I would surely recommend and share your blog with my friends. I was looking for such in-depth blog. Keep it up and keep exploring and sharing your knowledge with us.
Hi there,
Thanks for the kind words – glad you’re finding the info useful – that’s what it’s all about!
Cheers,
Alistair
Hi All
I was hoping to get some feedback. I have been “experimenting” with solar for a few years and have just bought a plot of rural land in WA and will be putting a caravan on it while I build a more permanent residence. Both I want to be if possible “off grid”. I have installed a 12v system in caravan (lights all 12v LEDs and 240v fluorescent , fridge which is also gas and mains, 12v water pump, 12v TV, 12v sound bar, and 12v TV arial, as well as charging points for mobile phones, PC etc). Lights and fridge as well as microwave (1100W), kettle (1000W) and oven are also mains and a gas stove and grill. I have two 145AH AGM batteries wired for 12V and a 2000W constant supply sine inverter all powered by a single 330W solar panel, also back up generator. I also have a 160AH AGM battery and 250W solar panel but was going to see how my set up goes then maybe use this for just lights, charging phones, TV, on an independent system not sure yet.I haven’t wired these us yet just option for later. I am also using a 30amp solar converter.
I’m a bit of a nerd when it comes to engineering so measure everything in terms of results of testing but am having issues reading my data to see what I have been using for just lights,TV, sound bar, phone/PC charging etc. I ran them for 7 days taking voltage reading every hour. My caravan is in a very sheltered place while I fit it out lots of trees, its permanent home will be very open to the sun and get a lot more. the average voltage in the morning (0600) is always 12.8V, this creeps up to about 13.4V to +/-11 o’clock then quickly shoots up to 14.6V which it stays at for 3 /4 hours then gradually drops to 12.8V which it stays at until next day. In 7 days of testing there has been minimal fluctuation in my figures except when I ran my 90L (150W) fridge on 12V. It nearly drained the batteries so not option for 12V. I’m top heaven with spreadsheets trying to figure out my battery status. My take is that I am using about 10% only, which would be good as I need some for inverter use for kettle, microwave. Any ideas on where I stand on power used/leftin my two 145AH batteries? Also would my 330W solar panel support also adding my spare 160AH battery to these two. I know they are not the same AH but the difference between 145AH and 160AH isn’t to much or am I wrong?
Appreciate any feedback, suggestion or possible pitfalls?
Hi Sean,
First off – wow! – what an opportunity! – and an amazing array of questions – all good!
And then, some comments:
Nerd is good, measuring is even better!
I agree your figures point to using about 10% of battery – excellent!
Running your gas fridge on 12V power was a great lesson (= don’t do it!) AND if the 150W fridge nearly drained the batteries, imagine what a 1000W kettle or microwave will do!?! (kill’em)
Now some questions:
Is your 330W panel 12V? (Voc about 23Volts). Given the size, my guess is no (12V panels top out at about 180W), so you need a proper MPPT regulator (not an eBay special) to bring the voltage down to 12V – if you paid $100 or less, my bet is it’s not MPPT.
Is your 250W panel the same Voc as the 330W? If yes, you can parallel that with your 330W but you’ll need a bigger regulator (330W on a 30A regulator is pretty much at the limit). Maybe best to go with your suggestion of running the 250W panel on a second regulator, with your 160Ah battery.
Then to the inverter – is it pure sine wave? If it’s a modified sine, it’s going to stress whatever 240V equipment you’ve got. Rather put it on gumtree and run the gennie for 240V stuff until you’re ready to transfer to your permanent house. Then you can get a pure-sine inverter to suit the battery voltage you choose for the permanent setup.
Finally some tips: a caravan setup is about one-tenth of what a permanent house will need – a minimum house setup would be about 3000W of panels. The other thing is battery voltage – 12V is fine for caravan systems – a house would need a 48V battery at least. The panels from the 12V system can be re-used, but in the permanent system the panels should all be identical, so maybe think about that as you build up the system.
Hope this helps in the meantime. Happy to discuss further!
Cheers,
Alistair
Hi all
What a great table of consumption figures. Thanks so much.
I just want to point out that a certain Cpap brand built for travelling have been chewing less than 6amp-hours for a good nights sleep for over 6 years now. (no humidifier) To prove it I can get a full nights sleep on a 7amp-hour battery (the size of the one for the caravan disconnect) when I take it overseas. These machines are tried and tested and cost no more. They fit in the palm of your hand and even have a NON HEAT humidifier option if you want it. Their opposition has just brought out a small model that costs a fortune and are acting like it is a huge breakthrough. I get so tired of people asking for special power needs at rallies and things when there are cpaps that have been running for years on a battery that fits in your pocket. Do your own research Australia and stop being ripped off by the cpap companies. Look overseas. In six years I have spent $500. Its still going strong after six years and that’s after buying it second hand. Easy to program and record your progress too.
Hi Hilto,
Good to know you found the consumption table useful – and thanks so much for contributing your very useful info on Cpap machines. I’ll update the 12Volt Blog accordingly!
Cheers,
Alistair
Thanks Alistair,
I have ordered a 500W PSW inverter.
One more question. On inspection of the dual battery system in my 2018 Jayco Basestation 23′ caravan I have found the batteries connected in parallel and all the caravan connections coming off the +ve and -ve terminals of one battery.
I have looked on the net and read that they should be off +ve on one and the -ve of the other. Then elsewhere found that either way is fine. It is obviously done this way for ease of connections as one battery is closer to the side where the leads come from. It would be a big hassle to change it as I’m sure the wires won’t be long enough.
Also, when I wire the inverter in, can I use the 2 terminals on the other battery that the rest of the caravan isn’t connected to? Otherwise there will be a lot of wires in to one set of terminals. Quite a stack of connections. Where on the stack should the inverter go?
Thanks for you help.
Cheers
Neil
____________________________________________________
Hi Alistair,
Excellent Blog. I’m very glad I found it. By far the most informative thing I have read about 12V electronics. Thank you.
I am living in a caravan in NZ and am wanting an inverter to charge my Macbook Pro whilst off grid. To future proof myself I also want to be able to charge an e-bike battery from it. It seems impossible to find the wattage required to charge e-bike batteries. I have asked in bike shops and inverter shops.
The battery I am looking at is a Giant EnergyPak 500, 36V 13.8Ah Rechargeable Lithium-Ion and the battery charger states it has input of 240V ~ 4A and output of 41.8V =-=-= 6A.
I am looking at a https://waveinverter.co.nz/shop/power-inverter/nomad-nps-1100w-pure-sine-wave-inverter/. Maybe 500W is all I need? The 350W one has a cigarette lighter attachment too which would be much easier.
I also asked the seller if I needed a circuit breaker in the power feed to the 1100W inverter and he recommended a 200A one (https://waveinverter.co.nz/shop/accessories/200a-circuitbreaker/). Seems huge. Do I need one at all? Do I need a remote on/off switch if it is wired in to a cupboard by the batteries?
By the way, I have 2 x 150W solar and 2 x 100Ah batteries.
Thank you for your time and expertise.
Cheers
Neil
In reply to Neil.
Hi Neil,
Good questions – and thankfully the short answer is: it doesn’t make too much difference either way.
With parallel batteries it is better to have one coming off the -ve and one off the +ve but the difference is tiny (milliVolts) – so the difference is not nothing, but it’s pretty close – so unless it’s easy, just leave it as is….
Same for the inverter connections – doesn’t really make much diff either way. The most important thing about inverter connections is to keep the cable as short as possible and thick enough to keep the volt-drop to less than about 0.1Volt. You can use the 12Volt Blog’s volt-drop calculator for that – for instance 1 metre cables should be 20mm (4 AWG) or thicker.
Aaah, and to your previous question about a remote switch for the inverter – good idea if it’s tucked away and hard to get at – if it’s accessible a 50A breaker/switch (e.g. Blue Sea) would be better, that way it draws zero when it’s off – some inverters still draw a bit when switched off using their remote-switch.
Hope this all makes sense – otherwise let’s keep chatting.
Cheers,
Alistair
_____________________________________________________________
Hi Neil,
Glad to know you’re finding the 12Volt Blog useful – all good!
About that inverter, looking at the specs you’ve given for the e-Bike charger, a 500 Watt inverter would be fine, with a bit of spare capacity too – and good to see you’ve got your eye on the pure sine wave ones – they’re the only ones worth having!
From the manual it also seems the 500W model has an internal fuse, so you’ll be protected if anything goes wrong with the cables to the inverter. You might look at an Anderson connector to make it easy to plug in and out too.
And don’t be tempted by the 350W one, it might handle the e-Bike charger but the cig-lighter plug will have to take up to 35 Amps, and that would stretch a friendship way too far!
And the 1100W is an overkill for your needs – plus it will use heaps of power just to keep it ticking over – bit like replacing your Honda generator motor with a V8…
(;-)
Enjoy!
Cheers, Alistair
Thanks Alistair,
I have ordered a 500W PSW inverter.
One more question. On inspection of the dual battery system in my 2018 Jayco Basestation 23′ caravan I have found the batteries connected in parallel and all the caravan connections coming off the +ve and -ve terminals of one battery.
I have looked on the net and read that they should be off +ve on one and the -ve of the other. Then elsewhere found that either way is fine. It is obviously done this way for ease of connections as one battery is closer to the side where the leads come from. It would be a big hassle to change it as I’m sure the wires won’t be long enough.
Also, when I wire the inverter in, can I use the 2 terminals on the other battery that the rest of the caravan isn’t connected to? Otherwise there will be a lot of wires in to one set of terminals. Quite a stack of connections. Where on the stack should the inverter go?
Thanks for you help.
Cheers
Neil
Hi Neil,
Good questions – and thankfully the short answer is: it doesn’t make too much difference either way.
With parallel batteries it is better to have one coming off the -ve and one off the +ve but the difference is tiny (milliVolts) – so the difference is not nothing, but it’s pretty close – unless it’s easy, just leave it as is….
Same for the inverter connections – doesn’t really doesn’t make diff either way. The most important thing about inverter connections is to keep the cable as short as possible and thick enough to keep the volt-drop to less than about 0.1Volt. You can use the 12Volt Blog’s volt-drop calculator for that – for instance 1 metre cables should be 20mm (4 AWG) or thicker.
Aaah, and to your previous question about a remote switch for the inverter – good idea if it’s tucked away and hard to get at – if it’s accessible a 50A breaker/switch would be better, that way it draws zero when it’s off – some inverters still draw a bit when switched off using their remote-switch.
Hope this all makes sense – otherwise let’s keep chatting.
Cheers,
Alistair
Alistar,
Thank you so much for taking the time to create this blog. I’ve been looking for this information for weeks and finally found it all in one place. You’re a superstar and saving lives, as far as I’m concerned. Keep up the good work!
Hey Michael,
No worries at all – great to know you’re finding the 12Volt Blog useful!
Cheers,
Alistair
Hello Alistair
Thank you so much for all the information here and on the battery page. It has made sense to me!
We purchased a new van that had a solar panel, enirgi battery and projecta battery charger installed but had no idea how they all fitted together or what they would power when free camping.
Using your guidelines I think we can free camp for three days before needing to go for a drive. We don’t have a large Ah/day usage.
We need some usb fitted in the van and I will now be able to speak to the electrician with at least some correct ‘lingo’ Thanks once again for all your research and presenting it so clearly.
cheers
Helen
Hi Helen,
Glad to know the info is useful – that’s what it’s all about!
Free camping is the best, and to do it with some confidence is just great.
Enjoy!
Alistair
Hi Alistar,
I have to agree with others, I’ve been on the net for weeks trying to find info and your blog and replies are so helpful.
We have recently started to go free camping and off grid for between 3 days and a week at a time.
We found on our first week trip we had to come back to a powered site mid way through to recharge our system up.
We have an Engel Battery box with a 125A AGM battery. We have a 250W solar panel that is connected during the day.
We are running a 110 CF Waeco Fridge (Yes old but still seems to work well enough) It seems to draw around 45Watts.
We have 5 LED lights each with an individual switch so not all are use at the same time.
We then charge our phones and UEboom (bluetooth music speaker)
During the day the solar is bringing in more than enough to cover the outgoings. We are finding the issue is overnight with the fridge running the battery drops significantly and then the solar is not enough to get it back up to fully charged while running the fridge. Hence after 3/4 days we needed power to get back up there.
Any tips for reducing the draw overnight? Is turning the fridge off overnight a possibility or will it have to work too hard the next day to cool back down? Should we get a smaller fridge or use an esky for the beers. (Reduce the amount of times the fridge is opened)
Should we mount the solar panel outside the vehicle so when driving between sites we get charge. We tend to move every two to three days to a new location so there can be 3 to 5 hours of no charge to the system.
I appreciate any tips you can give me.
Thanks
Jenny
Hi Jenny,
Apologies for the delay in replying – we’ve been away! And thanks for the positive comments – glad you’re finding the 12Volt Blog helpful!
Plenty of great questions, so let’s start with the CF-110 fridge – heaps of space, but yes, being an older fridge it doesn’t have the upgraded insulation of the newer CFX range, so it’s going to draw more. My table above says about 65Ah per day average, but that’s for 80 litres, so yours will be more than that, probably above 75Ah/day. So you’ve definitely found the main culprit – now what to do?
The 250W solar will give you an average of about 75Ah/day in Perth – so this is right on the edge – any cloud or camping in Tassie (v.litte sun!) and the system will be going downhill.
The 125Ah battery will also be working pretty hard, but if you only camp every month or so this will be okay (see blog posts on 12V battery life), although bigger would better to get through cloudy days.
So battery & solar are marginal, but the real issue is still that fridge.
Getting an esky for the beers would help, but probably not enough, and adding a smaller fridge would mean the 12V system now has 2 fridges to run – so not really great options.
So how wedded are we to the CF-110? The biggest in the CFX range is 65 litres, and if this is enough, then hey presto, we have a solution! (about 30% less power draw).
But if the CF-110 is a must-have, then there are a few things we need to do.
First is to get a cover for it – this will reduce the amount of “coolth” being lost and therefore reduce the power consumption.
Second, double the battery size – this will store more for night-time use, and see you through cloudy periods.
Third, we simply need to get more power in, so I reckon another 150W of solar would do it.
Maybe start with the cover and see if that’s enough to get you through – if not, well then it’s either the CFX option, or more solar and battery.
Hope this helps!
Cheers,
Alistair
Hi Alistair,
Thanks for getting back, this time of year I’m sure everyone is off camping. I hope you had a wonderful time.
Yes the fridge it seems is the next item on the list to replace. It does have a cover by the way, it’s just old and doesn’t zip closed anymore. When I mentioned getting a smaller fridge I did mean as a replacement to the existing one, not as a secondary. It just means we put the beers in as we drink them so there are always cold ones :-). Any tips on fridges? We were thinking engel or waeco. We just need to save the pennies as they seem on the pricey side.
I went camping solo for 3 nights just this week and had no issues with power as I turned the fridge off overnight for the last night and everything stayed cold and I had 61% battery when I left to drive home. It had been cooler weather so the fridge was not working anywhere near as hard as when we went for the week.
The engel battery box takes a maximum 140 battery and the battery shop I went to only had the 125. I’ll definitely get the biggest one next time it needs replacing.
We are hoping to go camping more often but for now it will be approx once every two months and only for a weekend/long weekend so for the time being we should get by ok. It will give us time to save for next Xmas when we can get away for longer trips.
As for extra solar if we had a solar blanket can you connect that into the system so that both are pumping into the battery? I’ll have to look into that more. Are they linked one to the other and then to the battery or do they both go directly to the battery?
I’m already starting to think I should have got a bigger trailer 🙂
Cheers
Jenny
Hi Jenny,
Yep, I agree that replacing the fridge is probably next up – Waeco & Engel are two top brands, although Evakool is also worth looking at – they’re Australian owned and have a huge range of price-quality options.
Your 61% after a few days sounds pretty good – switching off can help (if the insulation is good, and outside temperature cool) – and of course not having the fridge in a hot spot (the back of my SUV goes over 50°C – easily) means it doesn’t have to work so hard.
Solar blankets: the ones I’ve seen often have the regulator close to the panel (not good – see blog on Folding Solar Panels) – and if you’re reading 61% on your regulator it sounds like a good one. If your regulator can handle the extra Amps from the blanket, just connect the blanket’s solar output direct into the solar terminals of your regulator. If your regulator can’t handle the extra input, then simply put the blanket’s regulator-output direct onto the battery.
Happy camping!
Cheers,
Alistair
Good idea would be to install a DC-DC charger to charge the battery while you are driving and then use the solar while at camp.
Thanks again Jerry – agreed! – there’s a bit on DC-DC chargers in the blogpost “How to Charge 12Volt Batteries”.
Cheers,
Alistair
you have made a simple man understand the basics of 12 volt camping in 5 minutes where i have been on the net for hours, you should publish this piece thanks gary
Hey Gary,
Glad to know it was useful mate – that’s what it’s all about!
Cheers,
Alistair
Hi Alistair,
Great bit of information and advice, thank you.
I’m new to this camping caper and any advice on running equipment will be greatly appreciated. I want to take the wife and 3 kids free camping this year for the first time and don’t want to end up with a disaster and the wife and kids not wanting to free camp again!!!!
I’m looking at buying a Maverick 145AH deep cycle battery to run a 70 Litre fridge, 4 bar LED Lights on dimmers, sink tap and x3 devices (Phones). I already have 140watt portable solar panels.
All equipment will be “plugged” into a Thumper Extreme battery box.
I believe the fridge draws 0.16KWH/24 Hours which I think is 45AMP Hours per day.
Will my solar panels be enough to replenish the battery each day (Depending on sun) I believe the battery can only be allowed to discharge 30% capacity.
Any advice will be welcomed.
Regards and happy camping
Richard
Hi Richard,
Free camping can be great fun – and having a few basic home comforts makes all the difference!
So, the fridge – that’s going to be a life-saver but it’s also about 80% of the power draw, so let’s focus there first. Your 45Ah per day agrees with the figures I’ve got for a 70 litre fridge, so that’s a great start.
Now comes the question – how long? – are you planning to be out there for a few days or more like a week?
If it’s just 3 days then the fridge will use 45×3= 135Ah during that time, and the 145Ah battery will be just fine, even without help from the solar. (the 30% discharge figure is only for long-term installations, for camping we can use 100% of the capacity – have a look at the blog on batteries).
But if it’s for a week or more, then we need to find that 45Ah for the fridge every day – so this has to come from the solar. If we take Perth as an example then using the solar calculator it comes out at about 150 Watts of solar to support the fridge – so you’re close, but not quite there, especially when we factor in the other 12Volt stuff you’ve got.
The other thing is if the 145Ah battery will fit in the Thumper box. A battery box simplifies things heaps, with all the plugs, gauges, etc. so stick with that, and if you can get the 145Ah in there, great.
Might also be good to check the blog on portable solar and then have a look where your regulator is.
Ok, enough for now – aahh, one last thing – the more you can keep the fridge closed, the less power it’ll use (I’ve also got kids, so good luck with that!)
Cheers,
Alistair
Hi Alistair,
Just wanted to offer a quick thank you – I’m helping a friend set up a solar power system for his mobile (and currently, only) home, and your blog is by far the best source I’ve found on the subject. Your being from Australia is an unexpected plus – living in Israel, we enjoy(?) similar weather patterns, so the data is all the more relevant.
Keep up the good work, mate!
Hi Sagi,
Thanks for the kind words – and really glad you’re finding it useful!
A mobile home can be a challenge but usually the big plus is plenty of roof space for panels!
Good luck with it – any tricky questions, just give us a yell.
Cheers,
Alistair
Hi Alistair I’ve finally found out how to run my 12volt 240volt 2 way 72 watt fridge continually on 12 volt while on holidays,and that is by replacing the old 2 older 64 watt solar panels with two new 250 watt panels and replacing the 380 watt mppt30 sunyoba controller with a new one that can take 500 watts at 12 volts this will keep the two new 105 amp full river deep cycle batteries charged for 32 hours or continuously hooray no more turning off the fridge every time I park and stop the engine Apperently my boss said Ito understand it I had to understand Ohms law which is volts x amps equals watts and watts divided by volts equals amps thanks Alistair
Hi David,
Great that you’ve found an answer that works for you!
Yep, that’s a serious amount of solar – 500 Watts! – that should keep your batteries very happy indeed.
Yeah – good old Ohm’s law -can’t beat it, and it’s right every time (;-)
Cheers,
Alistair
Hi Alistair Will a 50 watt 3way fridge flatten my 2 x105 Deep cycle batteries while using 12 volt power after all Winnebago would have known that 2 batteries is all that’s required.thanks alistair
Hi David,
50 watts sounds a bit low for a 3-way fridge – they’re usually closer to 150 watts or so.
Is it possibly a thermo-cooler?
Have a look at the blog-post on Fridges – there are some clues there about the different types of fridges.
Cheers,
Alistair
Hi Aaron the previous owner of my Winnebago replaced the 80 litre 3 way fridge with 12 volt 240 volt upright fridge which will flatten the 2 news deep rivers 105 batteries quickly I do a lot of free camping so I need a fridge the van has 2 solar panels producing 64 watts each and the fridge which is an aldis special called a ybeier produces 72 watts it ha a seperate freezer and it runs very quiet and reliable but I have to turn it off when I stop my engine otherwise it will flatten the house batteries within an hour Should I replace the fridge with a 3 way fridge or should I try and increase the solar capacity Thanks Aaron any advice would be very much appreciated David
Hi David,
Apologies for the delay in replying – I’ve been dealing with quite a bit of spam lately.
A 3-way fridge is very greedy on 12Volt, so when you’re parked up it switches over to gas, so it shouldn’t take any power from the batteries when the vehicle is stopped.
When you’re travelling along, a 3-way fridge takes power from the 12Volt system to keep things cold (for safety reasons we can’t use gas during travel).
I’m not sure what the replacement fridge is – sounds like a Waeco upright or similar. These are the most efficient if you’re free camping but they will still use about 90Ah each day – this means your 2x105Ah batteries will last about 2 days without charge, which is not great, but it’s ok. The batteries also get charged from the alternator while you’re travelling along.
To replace what your upright compressor fridge has taken out of your batteries, you will need quite a bit of solar – probably around 250 to 300 Watts in total. If this sounds a bit much for your setup then maybe reconsider the gas option which is back to the 3-way fridge.
That aldi fridge sounds very much like a thermo-cooler fridge – if that’s the case then you’re using close to 100Ah each day which is huge – you’d need well over 300 Watts of solar to keep that going, so that’s not really practical for such a small fridge. (have a look at the blog post on Fridges too).
Hope this makes sense – if not, let’s keep talking!
Cheers,
Alistair
Those fridge draw figures are invaluable. Thanks for doing the testing.
I found with my 60 l compressor fridge to get a ‘real-world’ idea of consumption I needed to at least double the figures published by the manufacturer.
No worries Ziggy,
Yep, real-world figures rule!
You’ll also see that Aaron commented previously on this. He did some testing on his own fridge and found the usage was way more than he thought – and they were pretty similar to the figures in this Blog post too – all good!
Cheers
Alistair
Hi Alistair,if I put 2 more 105deep river house batteries into my Winnebago would that stop the 72 watt fridge flattening them.
Hi Alistair
I assume your power usage figures allows for fridge cycling?
Is there a rough guide to cycling on off times ?
Or are your figures for 24 hour continuous running
Cheers
Peter
Hi Peter,
The power usage figures are the total Ah measured every 24 hours, averaged over weeks and months of testing. So yes, they do allow for fridge cycling. Continuous running figures are very seldom realistic – it will get close to that when running as a freezer in hot weather but it will still cycle off now and again.
Glad you’re finding the info useful!
Cheers
Alistair
Hey mate,
Good to see you got the comments working. Yep. I’ll be testing the system out with 9 days off the grid, so we will see how it goes. Planning on 400W of panels, semi permanently mounted to a camper boat rack. Cheers for the information.
Yep, I’ve seen a few calculations about it. Did some testing – the Evakool draws about 600-800 Watts over 24 hours, so quite a bit more than I earlier imagined. I’ve ordered solar panels and a regulator, along with two 150 Ah batteries, so should cover it well.
Nothing as convincing as doing the testing yourself – nice one!
600-800 Watt-hours per day is about 50-67Ah/day at 12Volts, so looks like our tests that got 45-65Ah/day for that size fridge agree pretty nicely with your tests.
Always good to have real-world figures, especially when they agree – thanks for adding that!
Cheers
Alistair
Pretty great post. I simply stumbled upon your weblog and wished to say that I have truly enjoyed browsing your blog posts.
In any case I’ll be subscribing to your feed and I hope
you write once more very soon!
Thanks for the kind words – glad you’re finding the Blog useful!
Cheers
Alistair
I’m interested in knowing whether it is possible to have a simple solar panel to 12 volt water transfer pump connection – with no charge controllers and all that sort of thing
Hi David,
So you want to avoid the cost & complication of a regulator & battery, and are happy to use the pump only when the sun is out – right?
If so, the short answer is Yes, we can do that – and the longer answer needs some questions first.
Because a 12Volt panel gives us more than 12Volts – somewhere between 17 and 23 Volts – we will damage a 12V transfer pump if we connect it straight to the panel. But if we use a 24V pump, then it’ll operate quite happily – a bit slower, but it still works well.
So, questions:
– how much flow do you need? A small DC transfer pump can do around 15 litres/minute – do you reckon that’s enough?
– and how high does it need to lift the water? – so the height-difference between intake and outlet. Again, the same small DC transfer pump can lift the water by at least 5 metres – is that going to work for you?
So once we know a bit more about the application, we’ll be able to size the pump and also pick a suitable size panel for the application.
Cheers,
Alistair
Great article mate. 12V systems are very easy to mess up when not enough knowledge is applied. We are currently setting up a camper trailer to run a 55L Evakool Freezer. Enjoying the rest of your articles!
Hi Aaron,
Thanks for the kind words – much appreciated.
Nice fridge too – and while you’re in the setting-up stage, cabling to the fridge outlet is probably the most important thing. You’ll have seen the typical consumption is 45Ah/day (so just under 2Amps average current) but to calculate volt-drop on start-up we need to use the start-up current of around 6-7 Amps. If the cable run is under 5 metres then 6mm Auto would be a good size – you only want to do the install once, right?
Have fun!
Cheers,
Alistair
Having read your solar usage and requirements, we have a new motorhome, a conversion, and have noticed that so many of the new items have tiny lights , the solar panel itself, the standby on the TV the lights on the satellite and one or two others, although these little lights are tiny they must still draw quite a bit of ongoing power as they stay on continually..
Hi Fran,
Good question, and the short answer is yes, they do draw power, but fortunately it’s very small – down in the milliAmps. So compared to say the TV itself, the current is about 500-1000 times less.
This will not be significant while you are travelling and have power coming into your batteries (solar, battery charger, etc).
However, once you get home and the batteries are standing idle, that’s when those small currents become more significant, and they will certainly flatten the batteries over time. So it’s a good idea to disconnect the batteries altogether, through a heavy-duty battery isolator switch in the positive line. That way the battery is only subject to its own self-discharge, and will only need a top-up every few months or so.
Hope this makes sense!
Cheers
Alistair