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Onboard battery charger

J

JAJ

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Joined
Dec 17, 2003
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197
Location
Cleveland, TN
So, couple years ago I bought a onboard charger from BPS, 2 bank since i have a battery in the front of the boat that runs the trolling motor and one in the back for cranking the motor. At the time, i didn't have any electronics on the front of the boat, just at the steering console. Last year i got a deal on a nice humminbird so i bought it and mounted it on the front. Well, you guessed it, my front battery life took a hit. My question is, if i buy a second battery for the front, hook them up in series so I'm still running 12 volts, do you think that 2 bank charger will still work or should i upgrade?
 
I think you will want to hook them up parallel to keep the volts constant like you would do on jumper cables, with positive to positive and negative to negative. That will not change the volts but give you greater amp hours. Your battery charger may be able to handle it depending on the charger. I have mine set up with two batteries, parallel for the trolling motor and one on everything else and it works fine.
 
If you charge both batteries at the same time, you can ruin one battery. When the better battery is fully charged, the charger will still read that more charge is needed and the one that is fully charged will be overcharged. If you do this, keep a check on water levels in both batteries. When a battery is overcharged, they tend to "boil" more and evaporate the water. That is why a good battery charger slowly goes down in amps as the battery is fully charged.
 
TNLynn":mas41oq3 said:
If you charge both batteries at the same time, you can ruin one battery. When the better battery is fully charged, the charger will still read that more charge is needed and the one that is fully charged will be overcharged.
Click to expand...

This. You will ruin a battery. Don't ask me how I know. I did it with a 3 bank charger hooked to 3 batteries. I had 2 batteries in parallel so even though I had a bank for each battery the charger saw the 2 as one big battery. Get a 3 bank and disconnect the wires between the 2 batteries in parallel while charging.
 
Spurhunter":xrg3mwik said:
TNLynn":xrg3mwik said:
If you charge both batteries at the same time, you can ruin one battery. When the better battery is fully charged, the charger will still read that more charge is needed and the one that is fully charged will be overcharged.
Click to expand...

This. You will ruin a battery. Don't ask me how I know. I did it with a 3 bank charger hooked to 3 batteries. I had 2 batteries in parallel so even though I had a bank for each battery the charger saw the 2 as one big battery. Get a 3 bank and disconnect the wires between the 2 batteries in parallel while charging.
Click to expand...

You can accomplish this with one of those marine battery switches. When you get home, flip the battery switch to make each battery independent of each other and plug in your onboard charger. When you unplug the charger to go fishing, flip it to run the two trolling motor batteries together. Oh and put the switch where its protected but you can reach it easily. On my dads boat you have to get down on your hands and knees and reach up under a compartment to reach the switch. Not much fun when its cold and the floor is wet.
 

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