2oldman wrote:
I'd consider putting those panels in series if you go longer to cut down on line loss. Your controller will handle it.
mike-s wrote:
dewey02 wrote:
So can the Grape Solar 40 Amp PWM controller really handle those to 120 watt panels in series and still output to charge a 12 volt system battery? I didn't think it could, but you've said yes. If it can, then I would definitely want to wire in series. Thanks.
You do not want to wire 12V panels in series to connect to a PWM controller, even if the controller can handle it. Panels in series increase the voltage, but not the amperage. And charging always occurs at battery voltage, so series wired panels would just have their voltage pulled down to the battery's level, with little increase in current over a single panel. So there would be no advantage to doing so, in fact it would basically make the 2nd panel useless. Wire them in parallel - the panels will put out more current to the battery, guaranteed, and that's all that matters.
BFL13 wrote:
No. Solar controllers have a limit on total Voc in their specs. PWMs are in the 40-50 zone. Two 12v panels with 22Voc each is 44 and you need some margin for when Voc gets above rating, such as in the cold.
The only reason to spend more on high voltage MPPT for this job is the thinner wire but fatter wire is cheaper than a big MPPT controller. If the whole idea is to park in the shade and set out the panels where there is more sun, it is likely there will be some trees or whatever around and part of the time you will get partial shading. For that you want to be in parallel anyway, NOT series.
OK. Thanks. I'm glad I re-asked that question. What you've said is what I originally understood, but another poster said to wire in series and the PWM could handle it. As you can see, it gets confusing for folks trying to learn. I certainly appreciate the info that people are providing, and I'm trying to sort it all out.
