Posted by alistair on 01 Dec 2016 /
2 Comments
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To get Daily Peak Hours of Sun see Solar Irradiation for Australia.
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2 Comments
Hi,
I’m interested in the W Hours calculation.. If I am correct 350w panels X 5 hours (Qld) would only give 350 x 5 = 1750 watts which is equal to 12 Amps.
My calculation is that 1750 w would be 145 amps at 12V..
12 amps for a 5 hour day would not charge a decent sized battery?
Cheers
John
Hi John,
Apologies again for the delay in responding due to my spam-filter going feral on me.
Your first calc is good – 350W panels x 5 hrs = 1750 but I’m going be a pain and insist on Watt-Hours.
I’m not sure though where the 12 Amps comes from. You’re using a MPPT so maybe your 350W panels have a total short-circuit current of 12 Amps? If so, then the panels are at a higher voltage than 12V and the MPPT converts this to 350W/12V = 29 Amps for a 12V system. Over 5 hours (Qld) this would then give you 145Amp-Hours into a 12V battery. And if we have a nice 200Ah battery, the 145Ah solar input would take us from flat (zero) to over 70% (145Ah/200Ah), which is pretty good.
MPPTs can get a bit tricky to calculate – they down-convert the voltage to 12V, but they also up-convert the current – the watts remain the same though, so there’s no magic pudding in any of this…
Hope this helps.
Cheers,
Alistair