Can I Run My Batteries In Parallel?

Mossyoakglock · August 28, 2009

I am wanting to run some batteries in parallel but I'm not sure if I can. I have two trolling motor batteries in my boat. Each battery has a cable running off its positive and negative. So that makes 4 wires that run to the front of the boat where the trolling motor plugs in and all 4 wires meet at the plug. Since all the wires run to the trolling motor, can I still put the batteries in parallel, or since they all run to the same plug, are they already considered running in parallel? I attached a very crude drawing of how the batteries are ran to help explain it better.

brims · August 28, 2009

If the negative wires are joined together and the positive wires are joined together at the plug, then they are already in parallel. If there are 4 pins in the connector, then they could be in parallel or series inside the motor, and you'd need to take the motor apart or find a wiring diagram to find out what's going on with it.

pwall · August 28, 2009

If you have a voltage meter, you can test the voltage at the plug. That will confirm how the plug is wired, either parallel or series.

WaterGuy · August 28, 2009

Even thought you have 4 wires going into the plug, the plug could have jumpers built in so that you truly only have 2 outputs.

Or....

The mate to that plug could be jumpered.

By being in parallel you get the amplitude (power) while the voltage stays the same. In series you get voltage increase.

Many many years ago in the early days of lead-acid batteries, my dad inserted a large nail into the top of the battery and was able to tap out 6 volts. That was used for ultra-slow trolling.