Should I install a solar panel on the roof?

[jtcpartners]

I am researching the possibility and feasibility of installing a solar panel on the roof of my Jayco Seneca 36MS 37' Class C RV. When dry camping would a solar panel allow me to use the tv or 1 air conditioner? Are the results of installing solar on the roof worth it? If someone could explain this in novice terms the benefits of installing a solar panel I would greatly appreciate it. I'm just trying to decide if I want to further research this or just forget about it.

[pianotuna]

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.

[Almot]

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.

[pianotuna]

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.

[Almot]

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.

[pianotuna]

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

[Almot]

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.

[mlts22]

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]

Thanks again!

[KJINTF]

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

[Just_Jeff]

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?

[jtcpartners]

Thanks everyone for your information and thoughts. I have lots to consider and study!

[RoyB]

After playing this game plan of camping off the power grid for the past 5 years or so I think the best way to do this is to plan out all the low to medium wattage 120VAC things you want to run from an Inverter as well as the 12VDC items direct connected to the battery. This will determine how much battery capacity you will need for a one day/night run off the batteries.

This works great if you can re-charge your battery bank the next morning when allowed to run your generator by direct connecting with the trailer 30AMP shore power using the RV30A-15A long adapter. This will allow your "SMART-MODE TECHNOLOGY" Converter/charger unit to re-charge your battery back up to its 90% charge state so that you can do this all over again for the next day/night run off the batteries. For me this was the only successful way I could do it.

Having solar panels trickle charging your batteries during the day time when the sun is out good and bright will only add to less time needed to run the generator. You might get to skip a day maybe of even running the generator.

The generator is a required item to be successful as some days will be cloudy maybe even four or fives in a roll. You would be dead in the water then just depending on the solar panel. To be successful I think you must store all of the solar power using your larger battery banks.

We are able to run all the things we want to run now off our batteries and can do the 50% to 90% charge cycles for about 10-12 or so times in a roll until we have to do a FULL 100% charge state to the battery banks otherwise it will start doing damage to the batteries. This requires about 12 hours of running the generator using smart mode technology which of coure will not happen if you in a place where they won't allow you to run your generator that long of continuous time period. This is usually when we head for the house on our trips.

This is what I would plan for if you really want to start camping off the power grid with your trailer for extended times and be SUCCESSFUL about. This does not include using your air conditioner or high wattage microwave. It also gets exciting when the cold days are around and you have to use the propane furnace and high current 12VDC blower system for extended times. This cuts into your battery usage plan big time.

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....

This is why I really got very familiar with what I need to do to live off the batteries first and then adding solar will be icing on the cake.

It all takes alot of planning

just my thoughts
Roy Ken

[HiTech]

It depends if it would be worth it to you, if you are already running a genset for the AC (because it takes a big battery bank to run AC for just a few hours, basically regardless of how much solar you cram on top of a tiny RV roof).

You would save gas but that may or may not be a concern. It would keep your batteries in good shape in storage, but if you have power in storage and a great converter that may not matter to you.

It will let you watch TV for longer with no genset noise, when it is cool enough out not to need to run the genset.

Jim

[time2roll]

100w to 250w of solar should serve you well to keep two+ batteries charged. The batteries should have no trouble running an inverter to power a tv. Air conditioning not so much unless the entire system is scaled up about 20x.