Community Forums

Daryl molly · 09-27-2021, 06:32 PM

We travel in a 30' MH with limited needs for power; Ref is the primary, a Norcold 8cu. I am wanting to use a portable 100W solar panel to maintain batteries (2 deep cycle) and I would also be running the Generator as needed! Any thoughts on weather the 100W would be adequate? We dry camp for a max of 4 days on average. Thanks in advance!

JHinman · 09-27-2021, 08:59 PM

If you can keep the panel in good sun, it can certainly extend your dry camping time. 100 watts at 13 volts gives you something on the order of 7 amps at the best. My experience with a fixed panel is that I would often get a lot less than the maximum rated output, but a portable panel may do better.

If you get half the rated output for 6 hours, that is some 20 to 25 amp-hours. That can be a significant input, and if you get more that is all gravy.

UTTransplant · 09-28-2021, 06:59 AM

Short winter days or cloudy weather make a huge difference in available power. In our 27’ trailer, we used 300 watts and two 6v batteries with a 220 amp hour capacity. Seldom had to run the generator. You may be more power conscious than we were, but a battery monitor would be a good idea to first determine your real needs which will be at night (furnace and refrigerator mostly).

Marine359 · 09-28-2021, 07:22 AM

Our experience this last year with just a 110w bi-fold portable with 30ft cable to mppt:
1. 50% of the time we were camped in NP or SP totally canopied, so it was useless.
2. When we had sun we’d always find ourselves putting it away because we couldn’t leave it out when we left the campsite. It’s the first thing that would sprout legs.
3. Our panel puts out about 6 amps in ideal sun. Not enough to meet our consumption needs, even if we have it out all day. That’s because we have a compressor fridge.
4. Conclusion. If you have a compressor fridge, you need 300w on the roof. Works well charging our portable power station. Our LiFePo4 house batt can absorb 100% of the panel charge amps. Don’t believe it would work as well with AGM or FLA batteries.

Persistent · 09-28-2021, 08:02 AM

Quote:

Originally Posted by Daryl molly

We travel in a 30' MH with limited needs for power; Ref is the primary, a Norcold 8cu. I am wanting to use a portable 100W solar panel to maintain batteries (2 deep cycle) and I would also be running the Generator as needed! Any thoughts on weather the 100W would be adequate? We dry camp for a max of 4 days on average. Thanks in advance!

Two batteries maybe 200 amp hours. Mostly consumed in 4 days is 50 amp hours per day.

8 amps from solar for 6 hours daily is 50 amps.

Technically it is close to being enough. However, actual world conditions will not be optimum. It will help a lot, but ultimately there will be many conditions that will not be enough.

A good combination is to run your generator for 1 to 2 hours in the morning before the sun is strong and then let the solar finish a lot of the charge.

The generator powering your converter/charger can supply 30 amps or more. When batteries are deeply discharge they will absorb a lot of that. Later the batteries won't absorb as much. The low current from the solar can finish bringing the batteries up to 80 to 90%.

A good quality state of charge meter would help a lot to manage your needs.

John Hilley · 09-28-2021, 11:29 AM

Use a larger residential higher voltage panel such as 330 watt and a MPPT Charge Controller

ByeTheWay · 09-28-2021, 10:19 PM

If your fridge is electric only a 100 watt portable panel won't do much. I started with a portable panel and found myself moving it constantly to avoid shadows. It worked much better on the roof.

Daryl molly · 09-29-2021, 05:21 PM

I wanted to confirm a few things; we have the 2 way RV fridge. We are not using much else except lights (all LED) and we run water pump and furnace only when Generator is on. What battery charge minder would you all recommend? lets start there.

JHinman · 09-29-2021, 08:55 PM

If you are using lead acid batteries a good voltmeter works. You correlate battery voltage to state of charge. Years ago I picked up a little digital model that reads a narrow band of voltage to 1/100 of a volt. Worked really well, but I don’t know if it is still available.

The other option is a coulomb counter, which actually measures the energy going into and out of your battery. You can see the instantaneous current draw at any time. The lithium batteries need that technology because the voltage varies so little as the batteries are discharged. Victron makes a popular one, but I think there are some that are cheaper.

twogypsies · 09-29-2021, 10:31 PM

Quote:

Originally Posted by Daryl molly

I wanted to confirm a few things; we have the 2 way RV fridge. We are not using much else except lights (all LED) and we run water pump and furnace only when Generator is on. What battery charge minder would you all recommend? lets start there.

I think your 100 will do just fine for what you want to use it for with a supplemental generator. However, compare a 300 panel... you may be surprised at the little cost difference and you wouldn't have to use the generator at all. We had 300w and boondocked as long as we wanted. Fully charged by noon. Of course, we were in the West with lots of sun.

Once, we even spent a week in Apgar campground, Glacier Nat'l Park .... a week of clouds and rain and we were in the trees. We were able to park with the panels under a big open space and it got enough light; no sun, to charge enough. Of course, we really conserved because of that.

hclarkx · 09-29-2021, 11:08 PM

You'll be okay, but plan for expansion. Almost making it through without the generator will get old and with the low cost of solar, you may be going 200 or 300 in short order.

Arrange the panel and wiring so you can easily add a second and third panel.
Buy enough MPPT controller to handle two or three panels (very small incremental cost)

Your batteries will appreciate being fully charged more often and you will like not worrying so much about taking life out of them via excess discharging. And, did I mention wishing you didn't have to get the generator out to run for 20 minutes so you have enough charge to get through the night?

DavidEM · 09-30-2021, 07:20 AM

Quote:

Originally Posted by Daryl molly

I wanted to confirm a few things; we have the 2 way RV fridge. We are not using much else except lights (all LED) and we run water pump and furnace only when Generator is on. What battery charge minder would you all recommend? lets start there.

My Thor Axis uses about 25 amp hours daily for the same usage pattern as yours, but no furnace and no generator running. Since your batteries are probably 70Ah G27s and you shouldn't run them down below 50% routinely for best life, you are limited to 3 days with no generator or solar input.

With 100 watts of solar in a sunny camp site, you should be able to extend the 3 days to 4 or 5 days.

Battery voltage is a very poor indicator of state of charge. Voltage is dramatically affected by coach loads when you measure it.

A shunt based battery monitor (a coulomb counter as noted above) is a much better choice. Here is a good one I installed on my Axis: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

garage man · 12-06-2021, 09:18 PM

Quote:

Originally Posted by DavidEM

.

A shunt based battery monitor (a coulomb counter as noted above) is a much better choice. Here is a good one I installed on my Axis: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

I wish the had a better translation as it is all new to me and a little hard to understand but I am ordering one.

I have 1200 watts, 6 panels, 3 in series and then paralleled with a Renogy 100 amp MPPT. Despite this I seem to have very little capacity. Batteries are new flooded, 220 AH, 4 6volt paired to get 12 volts. That should give me 440 AH if I understand the math.

I will get this installed and see if I understand better what is happening.

rarebear.nm · 12-06-2021, 10:11 PM

Your math is fine. But understanding may still be a little off. With any lead acid battery you do not want to routinely exceed about 50% SoC without doing some long term damage. I know some others will disagree with the 50% value. That means of the 440 AHr capacity you should use only about 220AHr. With lithium batteries you can go to 0% or close to that depending on make.

Portable panels are nice in some ways. You can pretty well by moving them all day as the sun angle changes. That may be ok if you are in camp all day. Not so good if your driving that day or want to go somewhere. With a roof mount panel system it will recharge while driving. Also you set it and mostly forget about it, just works. Typically I see many people eventually installing between 300 and 600 watts of solar. May take an upgrade or two.

On our 5th wheeler we have 1050 watts and 4 6 volt FLA batteries. In four years it has always reached 100% SoC by 10:30 except once. That was above the Arcitic Circle under some trees in a deep canyon. It did reach 100% by 1:30. I designed that system with that capability in mind. Used commercial grade solar panels and not common RV panels.

I strongly urge anyone thinking about solar to do an energy audit first and key is a good battery monitor with a shunt. Many thread about doing energy audits. That way you use real data and not some guesses to plan your system. What works for someone else may have no bearing on what you need.