Got a 24V trolling motor, need a solar charger. Have wiring questions...

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DeanHensler

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I have a pontoon boat that stays in the water at the dock all summer. It is completely exposed to the sun. I recently installed a 24V trolling motor. To get 24 volts I hooked two 12V batteries in serial. This is working well and providing 12 volts to the boat's lights, gauges, ignition, etc on the main battery and 24 volts to the trolling motor off the second battery.

I want to hook up a solar charger so that I don't have to remove the batteries and take them home to charge them. How can I wire the solar charger up so that it charges both batteries? Here is the charger I'm thinking of purchasing. Amazon.com: Instapark? NEW All Black 10W Mono-crystalline Solar Panel with 12V Solar Charge Controller: Patio, Lawn & Garden

Here is a diagram of how I've got the batteries wired up right now. Trolling Motor Wiring Diagram.jpg

Thanks for the help!
 

bruceb58

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Re: Got a 24V trolling motor, need a solar charger. Have wiring questions...

You would need two of those solar panels and it would supply around 0.5A, maybe, to each battery. If you had a 100A hour battery that was 50% down, it would take 120 hours of sun to charge each battery. So looking at over 2 weeks to recharge the battery.

I would rethink the solar charging option. You would need a roof full of expensive solar panels for this to be feasible.

That panel is really only useful for keeping a battery topped off.
 

fishrdan

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Re: Got a 24V trolling motor, need a solar charger. Have wiring questions...

^^^ Correct, that panel wouldn't do much for charging depleted batteries.

Leaving a battery low on charge is harmful and will shorten it's life. So even if that solar panel would eventually charge a battery after a few weeks, the battery would be damaged over time from being left in a discharged state.

You would need a couple of big solar panels and controllers to charge the trolling batteries within a reasonable time frame, though I'm not sure the price would be worth it...
 

DeanHensler

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Re: Got a 24V trolling motor, need a solar charger. Have wiring questions...

Thanks for the replies. Putting the solar charging conversation aside, is there a way to wire a single charger that would charge both batteries at the same time?
 

bruceb58

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Re: Got a 24V trolling motor, need a solar charger. Have wiring questions...

You could put them in parallel and charge them or buy a dual bank charger. Putting them in parallel would be my last choice.

You can also get something like this that will charge 2 batteries in series(individually) from a 12V source like your alternator.

http://www.amazon.com/MinnKota-MK-2-DC-Dual-Alternator-Charger/dp/B001PTHKJY

Just get that solar option out of your head.
 

fishrdan

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Re: Got a 24V trolling motor, need a solar charger. Have wiring questions...

Whats your power source is going to be, 120V shore power, 12VDC? Marinco's 12/24 receptacle and plugs would facilitate charging off a single 120V charger, batts wired to receptacle independently, then a series plug for the TM and a parallel plug for the single charger. This option would cost a good bit of a new charger and I'm with Bruce that it's not the best option.... A 120V shore powered dual bank charger (or this one), would work best.

The MK Alternator charger Bruce posted would take a long time to charge as it's limited to 10amps/bank, long run times on the engine. If you run around a lot and use the TM little, it may work just fine.
 

bassman284

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Re: Got a 24V trolling motor, need a solar charger. Have wiring questions...

^^^ Correct, that panel wouldn't do much for charging depleted batteries.

Leaving a battery low on charge is harmful and will shorten it's life. So even if that solar panel would eventually charge a battery after a few weeks, the battery would be damaged over time from being left in a discharged state.

You would need a couple of big solar panels and controllers to charge the trolling batteries within a reasonable time frame, though I'm not sure the price would be worth it...

Actually that looks pretty good for someone who's out in the boonies and has a need. Smaller and less expensive than I would have thought. Any idea how much of the 8.25 amp max output would result in actual throughput to the battery?
 

Silvertip

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Re: Got a 24V trolling motor, need a solar charger. Have wiring questions...

For a 24 volt system you would need two panels, one for each battery unless you added a switching system that broke the series connection and put the two batteries in parallel. But even then, there would only be 4 amps to each battery. At $327 each, $654 plus the cost of two charge controllers makes this a very pricey setup. And at nearly five feet high and a little over two feet wide they take up a fair amount of space and at 30 pounds they are not light either. 8.2 amps is at full sunlight, for however long a period that is, is what goes into the battery. Much less on cloudy days and nothing at night.
 
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