Wiring batteries in parallel

[AaronW]

Hey all, I have a battery question.

My bass boat came wired with the electronics, aerator and trolling motor running of one 12 V deep cycle battery. At the end of a 12 hour fishing session the other day, the battery was basically complete drained. I was wondering if it's safe to wire two 12 V deep cycles in parallel to increase the amp hours. I have an extra one lying around.

If anyone has done this, let me know.

Thanks!

[MarkFromSea]

Yes.... If you just want to try it out first before hard wiring, I've used a pair of standard jumper cables to accomplish this for longer run times in my jon boat. It essentially doubles your available running time, slight deviation.
https://www.google.com/search?q=12+volt ... B336%3B384" onclick="window.open(this.href);return false;

[AaronW]

jumper cables .... good idea, thanks a lot!

[MarkFromSea]

You're welcome! I'll add, in my opinion, I'd stay off the highest speed on the trolling motor for long runs. I let the smoke out of a min kota pushing a much heavier boat for long trolling distances years ago. It's possible, it was just time or possible the extra available amps wasn't anticipated by the manufacturer. Short spurts at the highest speed has never been an issue since with the new minn kota.

The jumper cables allow me to place the additional battery towards the bow of my lil jon boat.

[BentRod]

Two things to be aware of:
Make sure it's parallel and not in series or you'll run 24 volts through your system.

When pairing two batteries to run together (parallel or series), it's advised to use two of the same size and freshness.
Otherwise, an old or depleted battery can act like a leach and shorten the life of a new battery over time.

This website is geared towards RVs, but the concept is the same and there s a lot of good info here:
http://www.marxrv.com/12volt/12volt.htm

[hewesfisher]

When pairing two batteries to run together (parallel or series), it's advised to use two of the same size and freshness. Otherwise, an old or depleted battery can act like a leach and shorten the life of a new battery over time.

^^^^^^Exactly. Using another battery of unknown age and capacity may be worse than the one you're using. Make sure you are using the correct type battery for your trolling motor, it needs to be either a true deep cycle or dual purpose (most RV/Marine batteries are). Smart to match your battery to the load as well. Determine the max amp draw for your trolling motor then select a battery with the highest reserve capacity you can afford.

As long as you wire in parallel, you retain 12v, and your motor won't care if the battery has 50 minutes reserve capacity or 1000 minutes reserve capacity. The "extra amps" won't hurt your motor, it will only draw what the motor requires for the speed you're using. You could connect 4 12v batteries in parallel and it wouldn't matter, the motor still sees 12v and will only use the current required by your power setting.

All extra capacity does is allow you to run longer on a single charge. However, you do need to think about battery maintenance and charging. You now have twice as many batteries to charge, so your recharge time will be double unless you have two chargers or a 2 bank charger.

[AaronW]

Thanks for the info everyone.

Sounds like I've got a decent setup to handle this with a pair of 12v batteries and a dual bank charger.