This is not a RV application but there seems to be a lot of solar knowledge on here so I thought I would ask.I run a 12V system in my remote cabin for LED lights and RV size water pump and CD player. I charge the batteries (2 12V deep cycles) every couple of days or when they get down to about 12.2 or 12.3 V. To charge the batteries I hook up a 4,12,25 amp auto charger and run it in auto mode. The charger is powered from a Honda E850 generator. I recharge to 90% or so then shut down the generator.When I leave the cabin I leave the generator running with the charger hooked up. It runs out of gas after about 8 hours so the batteries never get back up to 100% unless I take them home and let them charge for a day or so.What I am thinking of doing is installing a solar panal to bring the batteries up to 100% while I am away from the cabin. I only go to the cabin every couple of weeks during the summer and not at all during the winter so a solar charger would have lots of time to bring the batteies up to 100%. The main issue with solar in my application is that the cabin is in heavy timber in a rain forest on the north coast of BC so it gets very little direct sun light even on a sunny day.Can someone suggest how much solar panel (watts) I would need to charge, and keep my batteries charged, in this environment?Thanks for any inputStew

Solar in the woods is a waste of money. You get zip no matter how many watts you have. In the situation, IMO just take the 2 batteries back and forth to home/cabin. Same routine at the cabin for partial recharges, but now at home get them to full and leave them on a maintainer charger.I use this Can Tire one that works great and holds at 13.4v forever, so it is a perfect Float charger. Often on sale at half price. Watch the flyers.http://www.canadiantire.ca/en/pdp/motomaster-eliminator-intelligent-battery-charger-2a-0111506p.html#.VFAfGGd0xjoBTW don't get any solar anything at Can Tire! They want at least twice what they ask at proper solar places.

What about a small hydro turbine, if there is any flowing water?Google: micro hydro

SunElec.com They sell 100 - 150 watt panels, even some in the 250+ watt range. The price is reasonable, a lot less than what you have tied up in the generator. I have a 400 watt system on my motorhome, and it can make up 120 amp hours daily. I could watch about 5-8 hours of TV via a 300 watt inverter, and still get a full charge the next day. . Check out HomePower.com Magazine. They offer a lot of information in each magazine, and include the ad from Sun Electronics above. Good luck,Fred.

A friend of mine had a similar issue with a cabin on his property that is mainly a glorified shed. It wasn't too expensive to slap up a set of panels, a PWM controller, and some LED lamps to light the cabin and the outside.If things got too low (around 50-60% SOC), he had an el cheapo Harbor Freight ET800 clone generator that he would fill up and let clatter away on the porch of the outbuilding to charge the batteries using a cast-off car battery charger. After a few hours, it runs out of gas and shuts off... but the 800 watts is good enough to get the batteries to 90% or so SoC, where the panels can go from there. Of course, the generator isn't quiet... but the only things that will hear it are some deer and an armadillo or two.

Best shot for solar is a pick the sunniest spot and use some high voltage panels and MPPT controller. Good chance it will fail to maintain the batteries in those conditions. Especially in winter. You can spend hundreds and it may not work.Partially charged batteries are easy to freeze and get ruined.I agree with bringing the battery home.For in season consider an extended run fuel tank to get a 24 hr 100% charge as you leave. But again by the time you haul fuel you may as well haul the batteries back and forth.Do you have a picture showing some sun?

Solar Question | Good Sam Community

42 Replies

Almot
Explorer III
Oct 30, 2014
Meanwell-shmoozehell. The entire energy budget of the OP is probably 20 or 25 AH a day. I don't know what possible logical reason can be there - other than difficulties of getting big panels to this location - to run a generator and then finish it up with small treetop solar, rather than doing it all on a big-wattage high-voltage solar.

... should cost less than one Morningstar 30a mppt controller.

Morningstar makes 30A MPPT controller?
jrnymn7
Explorer
Oct 30, 2014
He has two 12 volters in parallel, but yes, the purpose of the solar is to float, not do an 80-100. The Mean Well will more than handle that part, within the OP's specified time frame.

And because the Mean Well has adjustable voltage, it can be set to a decent boost/abs voltage, as well as a suitable float voltage. Moreover, if the need arose where the batteries required a good top charge, or even an EQ'ing, due to lost capacity, falling or unequal sg readings, unequal voltages across each battery, etc., the Mean Well's 13.5-18v range can handle any job required of it.

According to the OP's original post, the issue is with the existing charger not getting the job done fast enough. But the Mean Well will put out ~ 40 amps, compared to the 25 amps of the existing charger. And because the rsp-500-15 has a high PFC rating, it will not overtax the generator while doing so.

As for how much solar will be required to supply 1 Ah / day, a small panel mounted up high, in the sun, (not on the roof in the shade), should easily provide enough power, on average, to replace the 1 Ah / day of self-discharge.

The entire set-up should cost less than one Morningstar 30a mppt controller.
Almot
Explorer III
Oct 30, 2014
jrnymn7 wrote:
The OP appears to only want to supplement generator charging with solar, not replace it.

It depends on how much "to supplement". 10% of his total 225 AH bank? Or 20%? Or more?

There such thing as a self-discharge current ~ 1AH a day for a pair of 6V batts. Small 20W panel will barely put out 5AH on a sunny day. In deep shade I wouldn't expect more than 0.5 AH or 1AH a day, i.e. it will barely keep the battery from self-discharging and will never bring the charge from 80-90 to 100%.

Yes, he needs a bigger "boat" to bring 200W panels.
jrnymn7
Explorer
Oct 30, 2014
Almot,

I believe BFL was suggesting supplementing the use of a more appropriate charger (on generator power), with the small panel, for continuous maintenance between charge cycles. The charger I suggested would indeed get the job done well within the OP's specified time frame of 8 hours.

The OP appears to only want to supplement generator charging with solar, not replace it.
BFL13
Explorer II
Oct 30, 2014
He has a jet boat. For all the giant solar stuff you guys are insisting on, then like the guy said in "Jaws", "You're going to need a bigger boat!"
Almot
Explorer III
Oct 30, 2014
Small treetop panel like 20 or 40W - yes, maybe, but he wants "full charge in a reasonable amount of time". Not to maintain the already charged battery. Now, charging requires a bit more wattage, so it has to be 200W or larger total panel area (considering shade), and on solid mounting brackets.

Stew - in low-light conditions a high voltage panel and/or amorphous panel is not a preference, it's a must.
BFL13
Explorer II
Oct 30, 2014
Several examples (except these are not small ones) here scroll down

http://www.wegosolar.com/pages.php?pageid=6
jrnymn7
Explorer
Oct 30, 2014
Awesome idea!
BFL13
Explorer II
Oct 30, 2014
For just a battery maintainer you can use a low wattage panel and it does not have to be on the cabin roof in the shade. I have seen such cabins with the panel up a tree nearby where the tree-top is in the sun. You can use really long wire and it won't matter for this low amperage job.
StewB
Explorer
Oct 30, 2014
Thanks very much for all the input and suggestions.

Security is not much of an issue as the cabin is only accessed via 2 hour jet boat ride. Very few people go into this area.

I bought the generator new in 1978 and it likely has at least 2000 hours on it so cost of generator is not a factor. Gotta love honda

I like the idea of getting a full charge in a reasonable amount of time with a good charger so I will investigate this opion.

I will also take a look at the high voltage panels option.

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