Solar window charger for two batteries?

[afinepoint]

Is there such a thing as a solar charger that can charge two batteries, swap to a safe float charge when done yet sit inside the RV? Or at least a battery tender that will hold the charge? The batteries are 24s I believe.

The idea is to keep the batteries at 100% while the RV sits in storage. My desire is to keep the electronics including panel(s) away from the weather and the curious.

I've seen those large units but they seem to be for use at the sites.

I inquired about solar chargers before but can't seem to pull up that thread.

Thanks in advance for any help.

Reg

[afinepoint]

Thanks

[Almot]

afinepoint wrote:
Brand and model for my needs? Let's go conservatively large.

Brand doesn't matter. Small "maintainers" are expensive, usually small, and only have a night diode, no controller.
Conservatively large? 50W is already enough for your bank if you disconnect the loads. Make it 80W if you feel like.

[Almot]

afinepoint wrote:
50-60w for two batteries?

Yes.
You only have 170 AH bank. Completely disconnected (which you should do), 170 AH bank will lose 30 AH in a MONTH. 50W flat panel, even in winter, will collect that much in a few DAYS. Unless it's covered with snow, or it's raining heavily all day long.

[afinepoint]

Brand and model for my needs? Let's go conservatively large.

[KD4UPL]

afinepoint wrote:
My concern is summer storms and the panels being unattended. If the panel(s) can withstand high winds, rain, hail and wind driven debris I'm sold.

If you're talking about a UL listed solar panel then it had to withstand 1" hail at 70 MPH to gain it's listing. I've had a panel blow off the roof of my camper (it wasn't fastened, just lying there) in a wind storm. It landed face down 10' away and was undamaged. I've got a good friend who had a horse step on one and not damage it.

Those little "maintainer" panels are extremely expensive on a watts/dollar basis and they don't do much. A real panel with a good MPPT charge controller will keep your batteries up and provide some useable power if you're camping without a hook-up.

[afinepoint]

hmknightnc wrote:
Search on solar in the forum to see a whole bunch of examples

Pulled up 452 pages. Don't have that kind of time.

Now that I'm aware of their durability just need recommendations on manufacturer, size for charging two batteries. I probably won't do a permanent mount just something that will stay put in all weather while in storage. I'll remove when moving. Is this impractical?

Reg

[afinepoint]

You only need 50-60W if all the loads are disconnected. CO detector often has its own AA batteries, and smoke detector probably has its own 9V battery.

50-60w for two batteries?

[Almot]

old guy wrote:
the propane and co2 detectors use up more than that {1.5 A) panel can replace.,

You don't need CO and propane detectors in storage. CO detector is for your lungs, if there are no people inside then you don't need it. Propane detector you don't need either, when propane tank is disconnected. The only thing that you need in storage is a smoke detector - if there are any people around to hear it.

[Almot]

afinepoint wrote:
If the panel(s) can withstand high winds, rain, hail and wind driven debris I'm sold.

The panel itself is very strong. Haven't heard of any problems with flat-mounted panels on L-brackets (i.e. ripped off the roof), and some people have huge 200-250W panels. You only need 50-60W if all the loads are disconnected. CO detector often has its own AA batteries, and smoke detector probably has its own 9V battery.

Make sure that "flat" panel actually has a few degrees slope, to shed
water and dust.

In very humid and hot marine environment (think tropical Mexico) you "might" have corrosion problems on panel connector box after some years, then you'll need a new panel.

Flexible panel like Unisolar is an easier option if you're not comfortable with brackets and drilling. You can glue it to the roof. But they are long, about 10ft. Check Amazon for Unisolar.

[mlts22]

If you are willing to take the dent in the wallet (they are $2/watt as opposed to conventional panels which are .75/watt) and a dent in efficiency, there are flexible solar panels that don't need a frame, and just attach to the roof with tape and caulk. That and a MPPT controller (I always recommend MPPT for the ability to capture every last watt from the limited space available for panels) will go a ways to keeping batteries charged. Given space, 100 watts is minimum, but ideally, 200-300 watts would be what one should look at (rule of thumb -- match the panel wattage to the total amp-hours of your battery bank. Not perfect, but effective.)

Of course, there is the option to have a fold-up stand with some panels on that. That will get you 100-200 watts depending on panels. However, once you get roof panels that handle the job regardless, it is hard to go with other means.

[westend]

afinepoint wrote:
My concern is summer storms and the panels being unattended. If the panel(s) can withstand high winds, rain, hail and wind driven debris I'm sold.

A solar panel is more durable than the roof on your house.

I'd go with the 100w+ model, too. Once you experience hands off battery charging, it's hard to go back.

[hmknightnc]

afinepoint wrote:
My concern is summer storms and the panels being unattended. If the panel(s) can withstand high winds, rain, hail and wind driven debris I'm sold.

Permanently mount on the roof using L brackets, no problem. A whole bunch of use have them and travel down the road hundreds of thousands of miles. Search on solar in the forum to see a whole bunch of examples

[2oldman]

old guy wrote:
and co2 detectors use up more ..than that panel can replace.,

CO1 not co2.

[old_guy]

if you are talking about the little 1.5 amp solar that harbor freight sell, save your money. they do not keep a battery charged. the propane and co2 detectors use up more than that panel can replace.,