Should I install a solar panel on the roof?

RoyB wrote:

Running everything in a 30AMP trailer from solar panels only will not work without a "hugh" battery system to store the solar energy for those times when your solar doesn't work because of not enough sun light to operate them....

Roy - what would you consider huge enough for a 30amp Class C to run everything except A/C and microwave?

I too would like to know what you consider a huge battery bank

We are NOT full timers but do go for a month or more at a time during the spring, summer and fall, no winters in the rig for us. For the past few years we have not been able to get the battery bank below about 65% SOC even with the 8 amp furnace blower motor running for hours in the evenings. The battery gets to 100% SOC typically by 11:00am this time of year and is only a meger 220amp/hr bank (two 6Vdc CG batteries). The 550 watts of PV array is more than a battery charger I consider it almost an unlimted power source during the daylight hours. It easily supplies the 40 amp draw from the compressed air system with no issues.

As you we do not run the microwave or the over head AC from the battery

Thanks again!

I'd do your homework to find out how much things cost, but with a 37 foot rig, there should be plenty of space for panels and a decent charge controller. With a few panels, you can easily get enough watts to offset the furnace's drain in the wintertime.

This won't run the A/C or microwave, but it will help with keeping batteries topped off, regardless of access to power.

jtcpartners wrote:
When dry camping would a solar panel allow me to use the tv or 1 air conditioner?

TV yes, AC no.

jtcpartners wrote:
Are the results of installing solar on the roof worth it?

Hopefully this isn't a trolling. If you are not DIY type, the cost will be much higher. It is worth it if you can afford it then, and if you need those benefits (see below).

jtcpartners wrote:
If someone could explain this in novice terms the benefits of installing a solar panel I would greatly appreciate it.

Quiet. No generator. Practically endless stay with enough panels, which is in your case feasible. Enough = 400W minimum total.

jtcpartners wrote:
I'm just trying to decide if I want to further research this or just forget about it.

You surely have to further research this if, again, you need those benefits. Mostly you have to research the conservation side of solar life. A lot of items - I would say most 120V devices - become impractical to run off the battery. Some of them you will have to learn how to live without, some need to be replaced. If boondocking is about a week, the task is easier, you can then allow battery charge to drop slowly, because you'll be going home soon. If the goal is a long term living, more conservation is needed.

Edit - PS: about microwave. This is one of things that you better turn off. You CAN use a microwave with solar, but you need a good inverter, and constantly keep an eye on your battery charge, and likely to limit the use of MW. Good news is that most things can be done on LP stove same well. For me it was easier to learn how to live without MW while boondocking. You can live without popcorn for a week, and reheating leftovers you can in a double boiler, aka Baine Marie like This one. Have found a matching lid for a few bucks. It is a slow reheating in 20 minutes, but the results are much better than MW. The food remains moist, not dried out and rubberized like in MW.

Here is a simple flow chart.

Budget-->Energy Audit-->Battery bank size-->number of watts-->PWM or MPPT.

Here is a link to the rather special spreadsheet that N8GS has created to help size solar battery charging systems!

Solar spreadsheet by N8GS

To what Pianotuna said, a disagreement - it can be number of watts first, and battery bank second. Or just maximize both as the budget and space allow. There is a rough estimate of 1 watt per 1 AH of battery. It won't hurt having "too much" panel - you will get some juice on even cloudy days then. And it will help having "too much" battery, as you will be able to ride through 3-4 rainy days (overcast will still give some charge, rain is worse).

With low draw - no MW, cat heater in place of furnace, LED lights, no 120V devices other than TV - you are golden. 400 AH bank will last 3-4 days then, with no sun at all, which doesn't happen very often. It is easier to crank the generator up though, so oversized battery bank is less important than too much panel.

You may try running a few 12V fans as a substitute for AC, solar will provide enough juice for that. Good fans, like Fan-Tastic. It's not the same though.

Hi Almot,

Solar is about battery charging. Generally if there are enough watts to effectively charge the battery bank, there are enough watts to meet the daily needs. A 400 amp-hour bank needs between 240 and 600 watts of solar.

Yeah, but it is not quite clear how many watts is "enough" to charge the battery on a cloudy day :) Or - on a cloudy day in winter... 600W doesn't sound unreasonable, in winter, with flat installation. For me, 400 AH bank would last 4 days or more (before dropping to 50%), if conditions would force me to. For somebody else - maybe less than 2 days. With the prices of solar panels now, I would rather err on the up side. His energy needs are not clear, TV is normally neither the only nor the biggest draw.

Hi Almot,

After flooded batteries are at 85% charge acceptance is about 12.5 amps per 100 amp-hours. That works out to 150 watts of panels. You can charge faster at a lower state of charge--but given the cost per watt I think 150 watts per 100 amp-hours is a good rule of thumb upper limit.

Below approximately 5 amps, it is hard to equalize a battery bank, that translates to 60 watts per 100 amp-hours as a lower limit.

And, of course, an energy audit is certainly a good plan.