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?

Using 120 AHs a day is a bunch for a couple. Check your energy survey again. 30 amp production for a 100 watt panel is very optimistic. 20 to 25 is more realistic. “Run the fridge” as in a residential unit?

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! :)

Yep....having a smallish generator might be better in the long run. You may end up under trees (if you're really camping and not "parking at a resort") and get ZERO out of those panels.

A 100 watt solar panel will produce no more than 100 w / 12v = 8 amps if you are using an MPPT charge controller. If you are using a less expensive PWM controller then you will probably only get about 6 amps out of a 100 watt panel. Either way, this takes absolutely perfect conditions: bright sun, perfectly aimed panel, no shading, and cool temperatures. This hardly ever happens. How many AH (notice the difference, Amps vs. Amp Hours) this gets you depends on where you are and what time of year it is. Here in VA you get the equivalent of about 4 hours of full output per day (8 amps x 4 hours = 32 AH.) If you are in the desert southwest it's more like 6 hours. If your in the Pacific Northwest or New England then only about 3 hours. Of course this will be slightly more in summer and less in winter.

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BFL13
Explorer II
Mar 22, 2020
Inverter time does add up. 10 minutes of MW at 125 amps is 21AH. Add some movie time 3 hours at 8 amps is 24 AH.

We do pig out on 12v stuff. I read somewhere that the average RVer uses about 50AH a day.

Furnace time!
BFL13
Explorer II
Mar 22, 2020
The OP said no winter camping (for now anyway) but here is an example with the 5er with six batts doing four nights with temp near freezing in January:

After two nights, next morning 12.1v (50%) and down 292 AH. (146/day)

Recharge with gen/charger (no solar) for two hours --constant 150 amps for 0.5 hr and 1.5 hrs tapering now down 78AH, restored 214AH. Figured that meant at 87% SOC of 584AH full. (Not new batts down in capacity near freezing)

So do third night, now down 227AH so 227-78 = 149 used. Now need another night, and 227 + 149 = 376 down, so would be at 208/584= 36% SOC. Oops, have to recharge again to top up to stay above 50% next day before going home.

The Trimetric monitor being very useful!

So can't continue with every second day recharge. Can restore 214 in the park gen time 9-11am and using 149/day, so can keep going if recharge every day.

You do get an extra 10% AH the first day from starting at full before going into 50-90s which can help on a weekend trip.
StirCrazy
Moderator
Mar 23, 2020
BFL13 wrote:
Inverter time does add up. 10 minutes of MW at 125 amps is 21AH. Add some movie time 3 hours at 8 amps is 24 AH.

We do pig out on 12v stuff. I read somewhere that the average RVer uses about 50AH a day.

Furnace time!

Ah, see I don't use the microwave when dry camping, and my TV/dvd is under 2amps. we started out with a tent trailer with two "car batteries" then went to a trailer where I put the four 6v batteries on it and converted everything to "power efficient" versions and the habit has carried on with the 5th wheel. with the trailer (no solar) I could go camping for a week in the Island winter on 475 amp hours, with the 5th I am not sure now as I have 480 watts of solar and I have never seen the batteries down when I go to bed in the evening. haven't taken the 5th winter camping yet though as we live in Kamloops now, but I have done late September in mid Alberta and in Banff with no power concerns.

Steve
BFL13
Explorer II
Mar 23, 2020
2 amps for TV/DVD is very low. I measured a couple of 32" TVs a few years ago in the 5er and got:

Samsung- Movie 70w, Standard, 80w, Dynamic 120w so divide by 10 for the amps.

Another TV (LG?) was: Vivid 8.2 amps, Standard 7.4 amps, Cinema 6.0 amps

The latest TVs might be fewer amps, don't know. It does show how your picture choice can matter.

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