A question/advice requested re: solar panels ...
I've got a question re: fusing/breaker for a solar panel setup I'm installing on a van conversion - just want to sense-check my thoughts against someone else's brains, maybe someone with more experience of solar than me
Thanks in advance!
So, my panels are 2x 270w Perlight Delta All Black ones… These: https://midsummerwholesale.co.uk/pdf...ack-54-270.pdf
As I understand it, it's good practise to fuse any power source as early as possible, be that a battery or solar panel.
I obviously don't want a fuse on the outside, that'd be a pain! So am thinking that as the solar cable will come in via an entry gland that's above a top side cupboard (cupboard yet to be built!), then I could pop a circuit breaker in that cupboard - nice & convenient.
My calcs, then some questions:
- Panels state open circuit voltage of 36.07v, so I guess that's the max volts.
- They seem to say (on the PDF linked above) current at Pmax is 9.06a per panel, so that’s 18.12 amps max.
- I'll be connecting the panels in parallel (argued with myself on this... series would increase the voltage and this may be good in low light UK conditions to make sure the voltage is higher than the battery, and so enable the batts to charge... But then again if then ONE panel is shaded, I think it'd mess up the other if in series... Parallel won't increase the volts but will work better if one panel in partial shade, if I'm correct? Plus, doesn't the MPPT serve to increase the volts if needed, provided it has sufficient amps being delivered to it, to ensure the volts are sufficient for the battery to accept a charge? Of course the MPPT will be very close to the batteries to avoid any further V drop, nice thick cables too).
So with all of the above in mind, fuse/breaker size I think is:
9.06a per panel, parallel so doubled as above would be 18.12amps. Could I get away with a 20a breaker? (keen on using a breaker as I'm a bit crap at losing fuses!).
1 - Anyone sense-check my thoughts & calcs above? All opinions welcome... If I've messed up somewhere or am wrong, please do say so! Getting this right is more important than my pride for sure
2 - With cable thickness/amps capacity calcs I believe you need to add 25% as a safety margin, I'm imagining the same is NOT true of a fuse, as the fuse is intended to protect the cable (not the appliance) from overload/overheating - am I right about this? If so, what are the thoughts about a 20a breaker when the max amps is 18.12a? All good? (I doubt the MPPT would complain if somehow 20a was delivered to it, it's a 50a MPPT - plus the cable I used will be rated above that anyway)...
3 - What are thoughts on fusing both the + and - cables from the solar to the MPPT? Overkill/not needed or advisable? Been told both by solar folks in the past! Opinions appreciated.
4 - If I did go with a breaker of 20a, do you think a car audio one would work, like: https://www.amazon.co.uk/Buwico%C2%A...0175T00AS?th=1
? (NOT an affiliate link! genuine question)... Issue is that the breaker linked is a 12v to 24v breaker, from what I understand this MAY be fine, the only risk being the plastic isn't rated to the (max) voltage of the panels, so a risk of arcing through the plastic... But surely there's a tolerance here?). Or would this maybe be better: https://www.amazon.co.uk/Circuit-Bre...15&sr=8-4&th=1
Hmmmmm that's it, I think!
Cheers in advance