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Brisco
06-07-2013, 07:29 PM
Greetings y'all.

I currently have a two battery setup in my Lund. Battery "A" is isolated and exclusively for cranking up my big outboard. Battery "B" is wired to power the minnkota. I'm considering adding a 3rd battery to this setup. I'd like a 2nd battery for the minnkota trolling motor.

My question is what is the best way to wire it up. I've considered a lot of different things and there seems to be a lot of varied opinions. The one thing I know is that I will not mess with current battery "A". It's staying isolated for safety purposes.

I have two basic ideas on how to wire in a 2nd battery for the trolling motor....

1. Wire them in parallel (pos to pos and neg to neg). I have a 12v Minnkota and I really don't want to buy a new motor to upgrade to a 24v system.
2. Wire them to and A/B Switch so that as one bat runs down I can just switch to the other.

Both seem to have their advantages and disadvantages.

By wiring them in parallel I would most likely never run down the combined batteries to an extremely low point meaning they'd have less cycles and theoretically the batteries would last longer. Also if I go this route my understanding is that two batteries in parallel will run longer at the same draw than they will separately which I think is a good thing. More run time is good!

The drawbacks to the parallel plan seem to come into play if one of the batteries has an issue. If one of the batteries is weak the 2nd battery in parallel is going to perform at the weak level as well. This would also shorten the life of both batteries. My understanding is that you would also need to make sure that your two batteries are as close to identicle as possible for the same reasons.

The last concern I would have is can my minnkota 3 bank onboard charger function properly if two of the three batteries wired to it are in parallel. In the instructions for the charger it shows you can use it for 3 batteries in SERIES but says nothing either way about PARALLEL. It's a 315D if want to know.

Anyone have thoughts?

dragonfly
06-08-2013, 10:42 AM
Brisco I switched from 2 group 24 and switchable to a group 24 marine start and 2 group 27 deep cycle ran parallel and run my battery tender just like normal with no problems you can see how in this section "what are we doing to our boat" I believe on page 4 along with the schematic hope this helps. dfly

Trackerg
06-10-2013, 04:42 PM
I installed a second deep cycle battery using the battery selector switch. I like knowing I have a full battery left when the one gets low on power.

SuperD
06-11-2013, 12:02 PM
I've never installed a back up battery to my starting battery since I've got 2 batteries in the front for the trolling motor.