Solar battery maintainer: worth buying? capacity needed?

[Elkins45]

I’m thinking of getting a solar battery maintainer for the trolling motor battery on my boat, since it’s normally parked out in the yard where it would be annoying to string an extension cord. How much trickle charge capacity does the average lead acid battery need? Are there any particular units you would recommend? Harbor Freight sells a couple. The cheapest one is only 1.5 watts so that’s like 0.1 amps and probably barely enough to maintain a lawn mower. I’ve seen a couple of 30 watt units, that’s 2.5amps and would likely do the trick, right?

 

[930.engineering]

.
First off, what capacity is your battery? With 50 - 100 Ah I'd get at least 10W or 1A. With 0.1A it could 'charge' the natural drain, but hardly to charge a weak battery. The latter task is better suited to conventional chargers instead of solar maintainers.

Btw, 'capacity' is what your battery has, explained in Ah (Ampére hours).

 

[FastLane]

I think some of the solar panels are not regulated so they tend to overcharge. I've also heard that they don't put out nearly the amount of amps that they state. 2.5 amps will charge up a deep cycle battery. It would take some time thats for sure!

 

[Vercingetorix]

If you really want something to work I would get an OptiMate. They have different panel sizes.

OptiMate Solar 10W - OptiMate

6-step 12V 0.83A sealed solar battery saving charger & maintainer

optimate1.com

 

[zzyzzx]

I have been using a 1.5W unregulated panel and it's worked great for years. I'd buy another, but the same HF one now is unreliable.
At 1.5W, the output is so low that you don't need a regulator.

 

[Elkins45]

Home Depot has a 2.5 W Schumacher for $28. I like that it’s a brand I’ve heard of and I like that it’s waterproof since I can’t put it under the windshield on an exposed boat.

Schumacher Electric Automotive 12-Volt Solar Battery Maintainer with Quick-Connect Clamps and DC Accessory Plug SP-200 - The Home Depot

With Schumacher’s 12-Volt Solar Battery Maintainer, you can harness the power of the sun to trickle charge your vehicle’s 12-Volt battery. The solar battery maintainer is ideal for extending the battery

www.homedepot.com

 

[Chevyc10]

I use a 15watt solar panel with controller from Deltran, charges winch battery on car trailer. Not used often. If you use boat often it may not fully charge.

 

[thastinger]

I’m thinking of getting a solar battery maintainer for the trolling motor battery on my boat, since it’s normally parked out in the yard where it would be annoying to string an extension cord. How much trickle charge capacity does the average lead acid battery need? Are there any particular units you would recommend? Harbor Freight sells a couple. The cheapest one is only 1.5 watts so that’s like 0.1 amps and probably barely enough to maintain a lawn mower. I’ve seen a couple of 30 watt units, that’s 2.5amps and would likely do the trick, right?

Save yourself some money, disconnect the battery, bring it into the garage and hook the regular battery charger up to it every 3 months.

 

[Elkins45]

I use a 15watt solar panel with controller from Deltran, charges winch battery on car trailer. Not used often. If you use boat often it may not fully charge.

I only need it to maintain it while off the water. When I’m using it I can plug in the onboard charger every night.

 

[Nesterenko]

I would go with a 10 watt charger, it should do the job of maintaining. No controller needed. I use a 7 watt panel and its just enough to keep the battery from losing it's charge. Mine is amorphous technology which is apparently better from what I've read because it charges better in lower light conditions than crystalline. It's made by Coleman.