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Old 01-21-2018, 02:23 AM   #1
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I'm hoping to get some advice on the practicality of installing solar on an old (1997 PW) Rv. It currently has a single size 24 house battery. Normally there isn't a problem since we are usually driving somewhere during the day even if we return to the same campground. But recently we spent 3 days without driving and the power ran low.......low enough to set off the CM alarm during the night. I ran the engine for a while and it stopped, but I'd rather not have to do this.

So...........I'm thinking about a solar panel to help keep the battery up in voltage while I'm relatively stationary.

Can anyone give me advice as to whether or not this is a good idea? If so, the size of the panel for this purpose? I think I can squeeze in a size 27 battery. Should I? Normal LA batteries ok? Gel?

Sorry about so many questions. Any help appreciated.
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Old 01-21-2018, 02:54 AM   #2
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Have you thought about replacing your battery? If the battery is weak, it will go down. You can go to AutoZone and have it checked. It is not an AGM, I would install one. Try that for starters; If it were mine, I wouldn't go near solar, enjoy that RT for now. If you want it downstream, it is available, but there are some really talented folks here that can discuss solar pros and cons. Stay safe, Ron.
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Old 01-21-2018, 04:16 AM   #3
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.

Solar is cheap these days.
And they are easy to install.
Lots of how-to video on youtube.
Lots of complete turn-key kits on amazon.

Plan on 100w of panel(s) for every 100AH of batteries.
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Old 01-21-2018, 12:54 PM   #4
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The first, and likely most important, question is how you camp.

If you are camping in areas that don't receive much sun, such as shady National Forest type sites, the solar will be a lot less effective. A 100 watt panel can turn into a 15 watt panel in the poor conditions, so it would take many more panels to cover even your fairly low usage, which I probably 20ah or less per day if you got near 3 days out of a group 24 battery.

You might be better off to add a second battery, if 3 days is about maximum and you camp in the shade a lot.

If you are able to get sun all, or most, of the time solar is great, but you need to have enough battery capacity to cover the poor conditions periods.
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Old 01-21-2018, 02:32 PM   #5
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Fresh battery (s) with more capacity would be the way to go.
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Old 01-21-2018, 03:08 PM   #6
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I use a folding portable 100 unit from Renogy. One of the panels broke due to my negligence and I've since added another 100watt portable folding unit. The Renogy comes with a decent PWM four stage 30 amp controller mounted behind one of the panels. I have installed the controller inside the Roadtrek, closer to the battery. This controller is adjustable for battery type and also has a direct cable to the battery for voltage readings and also has temperature compensation. All good things.

I have two 25' connecting cables so I can park under the trees and put the panels in a more favorable position and also move the panels during the day if required.

This system keeps up well for our boondocking needs even with the Fantistica fan running during the day and/or the furnace running at night. We also sometimes run a cell booster and charge various devices, and occasionally watch an LED TV with an amplifier on the antenna lead.

Our parasitic load is about 8 watts with a fan in the fridge and the newer style electronic absorption fridge running on gas with the gas engaged.

This all works for us with occasional genny usage to make up for extended cloudy weather and/or sub optimum solar conditions.

That Renogy unit is available for $259 on Amazon. The cheaper ones have cheaper controllers. The second panel I bought was an HQST which uses China panels vs. the German panels from Renogy and has a flimsier carrying case. I threw the HQST controller in the garbage as it was clearly inferior to the Renogy unit.

We really like this for extended(up to two weeks) boondocking. Genny pretty much only runs to fire up the microwave, toaster oven or run the AC for the killer attack Chihuahua if we are away for a bit and it's hot outside.

HTH and have fun. ttfn
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Old 01-21-2018, 04:47 PM   #7
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Thanks to all of you who responded. I might try adding a second battery and then see what further needs I have BUT that brings up a couple of questions.
1. The flooded type battery requires venting. Do the others? I have a dedicated compartment for the existing battery but it will only hold one.
2. I've heard that if you add batteries that you should not mix old battery with new one. That you should buy 2 new ones. True?
3. I'm assuming that the time needed to charge 2 batteries would be greater regardless of whether or not they're being charged by the engine alternator while driving or solar.
4. Is a "short" charge ( say charging up from 50% to 70%) harder on a battery than a "full" charge (50% to 100%)

Again, thanks for all the help on this..................slow learning curve on my end but with help I'll get there...............
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Old 01-21-2018, 06:00 PM   #8
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Quote:
Originally Posted by GallenH View Post
Thanks to all of you who responded. I might try adding a second battery and then see what further needs I have BUT that brings up a couple of questions.
1. The flooded type battery requires venting. Do the others? I have a dedicated compartment for the existing battery but it will only hold one.
2. I've heard that if you add batteries that you should not mix old battery with new one. That you should buy 2 new ones. True?
3. I'm assuming that the time needed to charge 2 batteries would be greater regardless of whether or not they're being charged by the engine alternator while driving or solar.
4. Is a "short" charge ( say charging up from 50% to 70%) harder on a battery than a "full" charge (50% to 100%)

Again, thanks for all the help on this..................slow learning curve on my end but with help I'll get there...............
1. They claim all batteries need to be vented, but in reality AGM can be inside the van, but I wouldn't put them in a sealed box.

2. True, if you go to two new ones get a matching pair, preferably 6v golf cart batteries

3. Two batteries will take longer to get up to about 70% full, but not double off the alternator, usually, but close. The time from 70% to full is going to be essentially the same for one or two, as you have enough amps as they taper.

4. Short charging will be faster, so you will recover a day or two of use faster off the alternator. Current recommendations for most lead acid, wet and AGM, batteries would be that as long as you get the batteries all the way to full every 7-10 charge cycles or every couple weeks if fewer cycles, battery life will not be significantly reduced.
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Old 01-22-2018, 01:57 AM   #9
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I have a single 12v deep cycle wet cell battery and a 100 watt Renogy solar suitcase. We have boondocked for five days with this setup on numerous occasions.
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Old 01-22-2018, 02:14 AM   #10
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I have a single 12v deep cycle wet cell battery and a 100 watt Renogy solar suitcase. We have boondocked for five days with this setup on numerous occasions.
I don't think anyone would argue that you can't go for days on end with one battery and 100 watts of solar. What would be of question is what the weather and site conditions are, and how much you drive. 5 days on one battery and shady conditions in the rain, would likely be completely different.

We have 300 watts of solar, but also have compressor frig, use the microwave off of the inverter, run fans, computer, tv/dvd, etc and can also go indefinitely off grid if it is sunny where we are camped. But--because we know we can't count on the sun all the time, we also have 440ah of battery capacity, that will take us for 5-7 days even in poor sun conditions with no driving. If we didn't have a lot of battery capacity, we would be done in a couple of days if not driving some.

My point is not to say folks are wrong in saying how long their solar will let them be off grid. The point is to define the conditions you do it under. I think we often mislead newbie solar adapters into thinking the maximum sun condition results we often quote, will be all the time, and this is just plain not going to happen.

Perhaps a conditions rated scale would be in order: For us":

Maximum off grid time with good sun all the time or down to 60% of the time---indefinite

Minimum off grid time with very poor sun all the time---5-7 days

Added days from driving times while camped--1 day of capacity per 15-20 minutes of engine running.

A similar list could be made for any battery/solar/alternator size system, and I think would be much more useful for the new to charging and off grid camping folks that are here to get answers.
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