combining (2) 12v batteries

I was wondering if anyone knows the proper way to wire 2 12v batteries together so I don’t have to switch cables every time the one battery dies.

Jumper wires.. +/+ -/-

make sure you use heavy enough wire… if your running your trolling motor on these batteries and it has 8 guage wire.. use 8 guage jumper wires.

Dave’s correct If you plan on running the wire a distance, like if one battery was up front the other in the back, you would want to make sure to add a fuse as close to the battery as possible, so you do not have a long run of unprotected wire, even at 12v’s there would be enough juice to cause you a lot of problems if you were to have a short along the wire.

Not sure that applies to your case, but just wanted to mention that incase it did.

just make sure to run them in parallel (+ to +, – to -) to maintain 12 volts, otherwise you will have a 24v system, which will ruin electronics.

Do you have to disconnect the battery cables to charge the batteries? If I have an On-Board 2 bank charger do I hook a bank to each battery?

You shouldn’t have to disconnect either battery to charge. You should be able to charge through one or both batteries, check the chargers manual though

you can charge both with 1 set of leads off your charger. Hook battry 1 on + Hook battry 2 on – it will evenly charge both. I had problems when I ran 2 battries on my old 12 volt not charging evenly with my on board using both leads.

does each battery take up a bank on the charger or are they on the same bank?

I am doing this myself. It depends on the charger, but if battery 1 and battery 2 is hooked parrallel 12v here it goes. Charger/bank 1 leads for + on battery 1 +, and – on battery 2 – . This will equal out any voltage drop between the two. You can then hook your bank 2 up to the starter battery or hook it up the same as bank 1 was. My charger wants both hooked even if one is not needed so I attatched it the same and its ok. (promariner cabelas 20a 2 bank) Good Luck!!!