Solar Battery Charging

[spasm3]

I thought about this a few years ago, and never bought anything. I am interested in charging and RV 12v battery and also in off season a 12v lawn mower battery.

Thinking about this battery minder setup with this panel. I have a camper shed thats 24 x 40 and i keep my travel trailer under it. it faces north south, so the roof gets good west exposure to sun.

Next question, Does battery size matter if they are in parallel ? Could i charge/(float charge ) an RV battery and the small lawn battery ( both lead acid) at the same time in parallel ?

Thinking about this charger , and this 120 watt solar panel.

https://www.amazon.com/BatteryMINDe...e&sprefix=battery+minder+solar,aps,765&sr=1-1


https://www.amazon.com/BougeRV-Mono...sprefix=solar+pane,aps,197&sr=8-23-spons&th=1

 

[hemitom]

Only one way to find out !

 

[AZjeff]

Not an electrician but the best orientation for panels is due South and the degree angle should be your latitude. 120W panel should be more than enough for maintaining.

 

[spasm3]

Not an electrician but the best orientation for panels is due South and the degree angle should be your latitude. 120W panel should be more than enough for maintaining.

Agreed, it will face west southwest. Will get plenty of sun.

 

[meep]

My RV has 3 150W panels and a 100AH deep cycle. I used a mppt charge controller. The panels and controller are all renology. The three panels are enough that I can telework out of it 40 hours per week with fan, laptop and large monitor. So if you are just maintaining, you can do less power. 1 150W panel is fine for both maintaining and charging. Yes, you can parallel the batteries, but I’d be judicious with fusing.

also, the controller should always have a battery on the back side of it, don’t leave it free without an anchor. Renology is a decent brand, a little better than entry level. Their panels are great. Their charge controllers are usable, but not commercial grade.

note - you won’t get full rated power with solar. I think the max amps I’ve seen in my setup is around 9-10A at 12vdc.

 

[wrcsixeight]

I expect 78 to 82 watts from my 12v 100 watt panel, aimed at sun, once it has heated up, around solar noon, within 3 months of June 21.

When solar is maintaining a battery, that was not discharged overnight, it does not need to hold battery at 14.4 for hours each day.

Yet,
Many lesser solar controllers will do that anyway, regardless and when the battery is indeed cycles deeply, and needs 4 hours at absorption, might only be allowed 2 by the lesser controller.

A programmable solar controller, with battery temp sensor, can be very worthwhile, when the owner knows how to adjust it properly, for expected depth of discharge.

Its hard to have too much solar panel, battety wise, very easy to have too little.

Its a PITA, to add.more solar panel, later, unless one oversized the wire from panel, to controller initially.

I recommemd no less than 2 watts of solar, per 1ah of battery capacity, minimum, and more more for agm or northern cloudy climates.

I lowered my battery ah capacity to achieve nearly this 2 to 1 ratio, and despite deeper discharges, achieved significantly better $ per deep cycle ratio.

I have a bluesky 2512i mppt controller, running since October '07.

I also have A cheapo ( 10$)pwm controller, that is tediously programmed to seek and hold 14.8v, no float reversion.

I also have an older Renogy controller which was a 20$ ols model clearance special, that just seeks and holds absorption voltage for 2 hours each day, no matter what, and honestly, the batteries it feeds, are doing well with this one size fits all algorithm.
It does have a battery temp sensor. i locate sensor in a hot spot, when only shallow cycles are expected, and back on battery, when cycled deeper. Also keep it on the GEL setting, despite the batteries being AGM.

 

[4WD]

Was looking at a small solar panel for my Jeep that sits for 2-3 weeks often. Most have a ”cigarette lighter” style plug - but doesn’t that circuit shut down when you stop the engine … ?

 

[ripcord]

Was looking at a small solar panel for my Jeep that sits for 2-3 weeks often. Most have a ”cigarette lighter” style plug - but doesn’t that circuit shut down when you stop the engine … ?

Some do, some don't. A lot of cars have a power port that stays hot with the ignition off.

 

[zzyzzx]

Not an electrician but the best orientation for panels is due South and the degree angle should be your latitude. 120W panel should be more than enough for maintaining.

120W is probably overkill.

 

[JHZR2]

I thought about this a few years ago, and never bought anything. I am interested in charging and RV 12v battery and also in off season a 12v lawn mower battery.

Thinking about this battery minder setup with this panel. I have a camper shed thats 24 x 40 and i keep my travel trailer under it. it faces north south, so the roof gets good west exposure to sun.

Next question, Does battery size matter if they are in parallel ? Could i charge/(float charge ) an RV battery and the small lawn battery ( both lead acid) at the same time in parallel ?

Thinking about this charger , and this 120 watt solar panel.

https://www.amazon.com/BatteryMINDe...e&sprefix=battery+minder+solar,aps,765&sr=1-1


https://www.amazon.com/BougeRV-Mono...sprefix=solar+pane,aps,197&sr=8-23-spons&th=1

I have the battery tender version of that. Set it up years ago at an old garage I used to rent that didn’t have power. Set up one small solar panel and it worked perfect. I used a 30w panel ideally angled with a clear view of the sky, and it had zero issues keeping my Chevy group 78 battery fully charged.

Dissimilar size batteries concern me more. That’s a recipe for overcharging one or undercharging the other. And can result in a fire. Not that you’re pushing a ton of current in, and it’s intermittent… but I’d personally prefer seeing different size batteries on their own charge controllers.