Poor man’s solar powered camping

[kenandterry]

I have a 9 watt solar charger (looks like small solar panel) equipped with cigarette socket style plug.

Is this useful at all for trickle charging two 12 volt house batteries in my Georgetown? I was wondering if it may help for extending my dry camping if I only have the refrigerator running.

Help anyone?

[carlsbad]

Nope.

[carlsbad]

Expanded answer: 12w at 12v equals 1 amp assuming 100% efficiency, which never happens.

Your fridge probably draws 6 amps.

Your panel will trickle charge your batteries but don’t add much useful life.

[Flybob]

No. Those small panels are essentially useless. They will not keep batteries charged even if batteries are disconnected from RV

[mogman]

Well Flybob, I have one on my Hummer and it keeps up with the drain from all the security features. If I turn it off the battery will drain in 5 days to the point where it will not start.

[TheGerman]

While responses here sometimes tend to go into total overkill, I have to agree a 9W solar panel is not gonna get you anywhere. I have a small travel trailer with a single battery and a 40W panel extends boondocking times but not indefinitely either.

Given that you have a motorhome you're probably better off running the generator for 30 min or an hour which will charge the batteries much faster than pretty much any solar setup.

[rlh1957]

If your batteries are topped off, not used at all, no draw, it would help maintain them in the unused... like in disconnected phase of storage. But still the possible 1amp of charge you'd get is less than a trickle charge would put out, with no way for it to boost if volts dropped. As mentioned above, hooking it to your car or TV batteries just to keep up with the clock, alarm system, and assorted sneak circuits that continually trickle volts out... it would keep you from coming back to a totally dead battery.

[babock]

A 9w solar panel will give 0.5A if you are lucky. Pretty much useless except to keep a battery topped off while in storage.

[UT_Grandpa]

Rule of thumb for lead acid batteries is that you can constant charge them at 1% of their Amp/Hr capacity, so a 100 AH battery can be charged at 1 Amp. You still need to check electrolyte levels and sulfation can occur.

In my trailer the CO detector and memory keep alive for the stereo are on all the time. I measured this at 50ma so, in theory, my two batteries would be dead (50% capacity) in about 2 months. So do some research on a 100-200 watt system (panel, charge controller, connectors, and wire) and you will be much happier.

[mnoland30]

A 9 watt panel will keep one battery from discharging if it is disconnected from the RV, and gets good sun every day. I had a small panel on my old truck for years, and the battery lasted 10 years, because it never ran down. I'd recommend you buy a larger panel on eBay or Amazon, with a good charge controller. The good charge controllers will surge your charge to prevent/remove sulfatin. They claim the batteries last much longer. I'm constantly amazed at how fast my batteries run down on their own when the batteries are not disconnected from the RV. Buy a cheap disconnect for your batteries while in storage. When I covered my trailer for the winter, I set a 20 watt panel facing west. That kept the batteries at 100% all winter. As mentioned, at 1%, you don't need a charge controller.

That said, I mounted a flexible 100 watt panel on mine, with a good charge controller, and quit even carrying a generator. I carry an extra 20 watt panel, for those rainy days to supplement the large panel. Putting the panel on the east side in morning and west side in afternoon, charges it pretty well even on cloudy days. The flexible panel hasn't held up that well in the sun, so I'll replace it with a glass covered panel.