Portable Solar Trickle Charger

[VetPartTimer]

Any recommendations for an inexpensive, portable solar trickle charger for when my RV sits in storage for extended duration?

Just wanting to keep my house batteries topped up, but also don’t want them overcharged.

[RickLight]

Something cheap!

Do you have trouble currently? You should be able to go many months without major loss. Is your disconnect really cutting it all off?

[Captain8]

I use this for my trailer and seems to work great. 20w solar charger.

https://a.co/d/4fmukMp

[VetPartTimer]

Originally Posted by RickLight

Something cheap!

Do you have trouble currently? You should be able to go many months without major loss. Is your disconnect really cutting it all off?

After spending $600+ on batteries, I don’t want to take any unnecessary chances of weakening them.

[VetPartTimer]

Originally Posted by Captain8

I use this for my trailer and seems to work great. 20w solar charger.

https://a.co/d/4fmukMp

I’ll check it out, thanks!

[BCam]

Keep in mind that the larger the panel, the greater the need for a controller. There's some variation in the recommendations so here's a search so you can make up your mind as to whether you need a controller or not:

https://www.google.com/search?q=what...hrome&ie=UTF-8

Personally, I have an old 50W panel that I hang on my ladder with a simple bracket that allows pointing it at a near optimal angle, feeding an inexpensive controller. Fortunately the rear of my MH is facing southward. My MH is in a storage yard and the panel has been undisturbed for a couple of years in contrast to the two cat converters that have been stolen. This is a temporary measure until I install my rooftop panels. I think 20W is adequate, 10W is minimal, the nature of your sun exposure.

I also have an Amp-L-Start installed that keeps my starting battery charged as well. Unfortunately, they are no longer available but there are other options including a dual bank controller or even two separate low cost panels, one for the house and one for the chassis.

[Stuff-Happens]

Amazon has lots of options at various price points…. Where I got my suitcase solar panel which I also use when parked in a shady area….

[Persistent]

A solar panel plus an appropriately sized solar controller will do the job. Cheap solar controllers are probably set to provide 13.6 volts maximum to the batteries. That is the maximum you want applied for storage purposes.

A better storage voltage is 13.2 volts. Some solar controllers can be set to provide 13.2 volts.

The panel and controller need to be sized to replace parasitic drain from the RV and self discharge within the batteries.

New batteries have very low self discharge. Old batteries have ever increasing drain.

Different RV's have different parasitic drain. A good way to know for sure is to measure voltage on the battery terminals. Get a cheap digital voltmeter at your local hardware. Fully recharge for 14 hours before voltage drops below 12.4 volts.

See attached file for how to store lead acid batteries.

[SailorSam]

Assuming you have sky access, I use a Coleman 2 watt panel. Just enough power to counter the self discharge rate. Won't overcharge. I use the provided alligator clips to connect directly to the battery posts. I get afternoon sun on the panel. Mine is outside in the elements. No issues after 3 years. Currently listed at $17.

https://www.menards.com/main/electri...os=4&exp=false

[wopachop]

Originally Posted by VetPartTimer

After spending $600+ on batteries, I don’t want to take any unnecessary chances of weakening them.

What did you buy? Its tricky with your situation storing the trailer. Leaving them hooked up to a small solar charger is not ideal. But even worse is letting them discharge too far.

Is the storage facility far away and does your trailer have a generator? You could ditch the solar charger all together and just visit the trailer once a month to start the genny and charge the batteries. You could disconnect the batteries and it would take several months to self discharge. Or you could pull out the fuses to the propane detector and anything else that might have a draw.

If you do end up with a solar charger and storage is close you could leave it hooked up for a week. Then disconnect for a month. Go back and repeat the cycle depending how convenient it is to visit storage.

I personally wouldnt leave the brand new batteries on a solar charger unless you were forced to be gone for say 6 months. Depending of course on how quickly they discharge. Will be quicker in the summer temps if its hot where you live.

[EngMarc]

I took a slightly different approach.
My 2022 wayfarer came with a go-power BP-PWM-30-UL which isn't terribly expensive (so if you want to add it to your Tiffin it wouldn't be much expense - about $130).

I had one 175 watt solar panel on delivery that comes with the Tiffin Solar package.

I purchased 6 x 100 watt Renogy RSP100DL-36 panels which are limber and can conform to a surface within reason. I mounted 5 of these on my roof (see photo) and have one extra for special occasions or odd setups. The Go-Power charge controller will tolerate 36 amps of charging from solar panels (about 600 watts). I'm getting about 14+ amps on a cloudy day and closer to 20 or so amps on a sunny day. Some of my panels are on the curved front so they don't get direct light when the flat panels do. This was by design for times when you're driving into the sun, these panels will charge most.

So, for two weeks now after installing these panels my RV has been isolated and holding a charge despite use and some losses.

I do realize this might be a bit more than most want to do but thought I would share as it is a project of mine to have the least amount of dependance on fuels and plug-ins. Ideally, I want to be almost independent when traveling and not have to burn generator time or plug in unless it's for a good reason (e.g. 25 degrees).

[Persistent]

Protect your new battery bank. Don't hook up a solar panel without a solar controller. If you get a panel big enough to keep the batteries charged, it is also big enough to "boil" the batteries dry.

Many portable solar panel kits come with an appropriate sized solar controller. Sometimes the controller is built into the panel. These are a good choice.

It is not helpful to follow others experience as to how big a panel is big enough. Different RV's and even the same models used by different owners consume different amounts of current when idle (parasitic draw).

Most people are successful when they choose a panel that is bigger than they need and include a controller that regulates voltage. As posted above 13.6 volts on the battery terminals is the maximum for long life and low consumption of water. 13.2 volts is the optimum for long term storage and 12.7 is adequate. Fully recharge 14 hours before battery terminal voltage drops below 12.4 volts. Monitor voltage frequently until you know how well your system will work.

12 volt Side of Life part 1
http://marxrv.com/12volt/12volt.htm
12 volt Side of Life part 2
http://marxrv.com/12volt/12volta.htm
Some of the information is a little dated, but it is still pretty good.

Battery University https://batteryuniversity.com/articles
How does the Lead Acid Battery Work?
https://batteryuniversity.com/articl...d-battery-work
How do battery chargers work
https://batteryuniversity.com/articl...-chargers-work
How to Charge and When to Charge?
https://batteryuniversity.com/articl...when-to-charge

You can get a cheap digital voltmeter at your local hardware store for about $15. Use it to monitor battery terminal voltage during storage and while camping. It is cheap insurance.

[Jkwilson1989]

Originally Posted by SailorSam

Assuming you have sky access, I use a Coleman 2 watt panel. Just enough power to counter the self discharge rate. Won't overcharge. I use the provided alligator clips to connect directly to the battery posts. I get afternoon sun on the panel. Mine is outside in the elements. No issues after 3 years. Currently listed at $17.

https://www.menards.com/main/electri...os=4&exp=false

2W is not going to counter self discharge or account for the propane detector. 2W is around 150 milliamps on a bright sunny day. Propane detectors draw about 75 milliamps day and night, rain our shine 24/7. Even in the best scenario of sunshine every day, the panel won’t keep up.

[BCam]

Originally Posted by RickLight

Something cheap!

Do you have trouble currently? You should be able to go many months without major loss. Is your disconnect really cutting it all off?

Most OEM disconnect switches don't completely cut the power. Things like propane alarms, etc. stay on. These are commonly known as parasitic loads and will run down your batteries over time. Likewise, starting batteries are subject to such loads. Don't drive your car for a month or so and see if it will start.

The only true disconnect solution is to disconnect the neg cable from your battery bank or, alternatively to install a mechanical disconnect switch between the battery post and neg cable. Even then, it's best to check on how long your batteries can go without charging. This can vary by battery type.