Tandem Set Up, Trolling Motor Battery

[CFRay]

I have a 12V MinnKota PD wired to one,three year old battery which works fine. I'd like to add a second battery in tandem. Do the two batteries need to be the same brand, same age? or can I add a new second battery of the same size/rating as the current battery? If anyone knows the answer and could respond I'd sure appreciate it. Thanks & Good Luck.

[Giant_Jackpot]

You can do it. The only thing is the power won’t last as long a two fresh batteries would. I would make sure the second battery is the same size and capacity as the original, no need for them to be the same brand. Connect positive to positive and negative to negative and you are good to go.

[Moose-Hunter]

As Giant_Jackpot said, yes it can be done. However, if you're looking to increase your running time, don't expect it to double. As water seeks it's own level, so will the interconnected batteries. When two batteries of different conditions are connected together, the newer of the two will attempt to "charge" the older unit. With this "cross charging" taking place, it will "wear out" the new battery faster to match the state of the older battery. Even with both batteries fully charged, they will discharge at different rates just due to age and number of duty cycles.

I ran this kind of set-up in my old boat and before I replaced the batteries in pairs, I saw very short battery life. Ultimately, replacing both batteries with new is the way to go.