Sizing panels to controller

mountainman · June 2019

I currently have 400 watts for camper dc loads. now I have the chance to get 4 310 watt panels.

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This will be for a 24 volt inverter system. For television fans phone charger etc. I'll b using a150 volt cc. 4 in series GC batteries. Panels 2 p 2 s . 100 foot on 10 awg remote array 4.52 volt drop but that's what I have. What amp mppt cc would fit. And what amp hr batteries would i need? I realize sizing is normally by loads. But with my finances this is how i have to do it.

Estragon · June 2019

1200÷24v=50a minimum, but I'd go bigger. Actual current max would likely be less, but IMHO it's better to go for a bit more capacity to run cooler.

4 x GC batteries would be ~225ah@24v. You could maybe do 4 x L16s for ~350ah depending on the application, other charging sources, etc.

mountainman · June 2019

So you'd suggest a larger than 50 amp cc. Since you suggest a 350 ah Battery bank . I suppose 1240 watts would normally put out 35 amps~? Thinking ahead. wouldn't i be able to add 2 more panels with a 80 amp cc? 1860 watts. 1860÷24 =77.5. Then if I used 8 GC batteries of 208 ahs. 416 x 29÷.77x .12℅ charge rate 1880 watts. 1250 watt hours on 4 day reserve. Or 4 l16 with out having any in parelel say 435 ahs that would put at about 11.5℅ charge rate.t hat give me about 1300 watt hours with a 4 day reserve. Am I doing the math right. Thoughts?

Estragon · June 2019

Your math looks about right.

Doing a single string of L16s has advantages (eg fewer cells to check/water), but 2 strings of GC has the advantage of being able to stay somewhat lit if/when a battery goes bad. GC also tend to be more widely available, easier to lug around, and may be a bit cheaper per WH.

Sizing panels to controller

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