Solar Questions

BeerBrewer wrote:
I'm interested in adding solar power and lithium batteries to our trailer, but I'm getting lost in the weeds.

For starters I calculated what I think would be our worst case power need (without using AC) if we went go off grid. First, it is just my wife and I, so no kids. We we wouldn't be using the Microwave, hair dryers or electric coffee pot when off grid. I calculated our power load to be about 120 amp hours a day. We wouldn't winter camp off grid, but I did assume that we may need the heat on for a couple hours, just to remove the chill. We'd only use the batteries for LED lights, to run the frig, charge up cell phones & tablets, run fans, to run TV and DVD player a couple hours at night and of course the other parasitic loads. Does my 120 amp hour estimation sound logical?

Assuming that my power swag is somewhat correct, I was thinking that we'd need two 100AH lithium batteries. Sound about right?

As for solar panels, I read that you can get approximately 30 amps from a 100 Watt solar panel, so I'd need four 100 watt panels or 400 watts worth in total. I know that I need more "stuff but does my plan seem logical so far?

Not clear what the 120AH is all for. We use about 75AH for 12v things per day not counting furnace. That 75 includes using the MW off a 2000w inverter off four 6s for say 15 minutes a day, plus watching a DVD movie.

With furnace add another 75AH for 150AH per day. If it is really cold all day near freezing make that over 100AH for furnace and the 75 stays the same whatever. We have seen 200AH days near freezing ambient.

A 100w panel will get in about 43AH lying flat on roof at 49N on a sunny day all day in May. It varies hugely by latitude and time of year and amount of clouds. There are on line tables for estimating that for different locations and time of year.

Lithiums are not magic. An AH is still an AH. If you do 30-80s with yours, then that is 50AH each 100AH battery. So we would need at least three for a 150AH day, no solar. (There are a lot of no solar days around here!)

I would never spend that on lithiums. I would spend that on ordinary 6s and a big inverter with a big charger and generator (100a charger and a 3000w portable gen) and live better with no scrimping, than pee away all the budget on Li batts. YMMV! :)