I have a question, that I am sure some Bass Resource expertise can help me with. I have a 12V trolling motor. I am thinking of getting two batteries wired in parrellel to get more fishing out of a full charge. I understand that I need identical batteries and all that good stuff, I want to know if someone has done this. Is this a logical solution or is taking another 12V battery still the most logical? It's just so much trouble to get back there and change it out.

You only "need" identical batteries, if you hook them up in parallel. Otherwise they can be used as they are.

If I were using two, I'd hook them in parallel, and charge them both when I returned, rather than running one down, and then switching to the other battery. A battery should be charged as soon as possible when it is run down. Bad things start to happen when a battery is at a state of discharge. In parallel, the first battery does not reach such a state of discharge. By starting with one and running it down then switching, you'll soon end up with two unequal batteries.

Identical batteries are recommemd for optimal performance but not totally necessary when in paraller. If in series, the MUST be identical.

If you want the most run time, connect them in parallel, you will get as much as 20% more run time over running one battery at the time. If you want that safety cushion and know it's time to head back to the ramp, run one at the time. When the first is run down, you will know it's best to start heading home with the other.

The heavier the load on a battery, the fewer the Amp hours they will give. A 105 amp hour battery may only give 75 amp hours of use under a heavy load (TM running on or near max). If there are two batteries in parallel, the load is cut in half so the two 105 Ah batteries will equal 210 Ah and that same load that was on one battery will provide about 180 Ah of use. That's 15 more Ah per battery than if running one at the time. Keeping the TM speed at about mid speed or lower will give you max run time.

Thanks guys! Two really good responses. Thats why I love Bass Resource, so much knowledge in one spot. You guys pretty much just reenforced my current train of thought. I was getting really tired of trying to change over batteries after one gets low. I'm just going for more time. I have been getting a good 6 hours of "hard trolling" out of a battery, I just wanted to push it on out to 8 or 9 for those good days. I am going to go with the parrallel 12V batteries. I think this is alot better. Ok....a question on charging. Can I charge them while still in parrallel? Would I be better off with a trickle charge or higher amp charge for doing that?

Yes, you can charge them in parallel but you have to use twice as much charger. You should use a 15 - 20 amp charger if going to charge them. The recommended charge rate is 10% of the batteries Ah capacity. If you have two 105 Ah batteries in parallel, that's 210 Ah, which for optimal charge should be 21 amps. A 10 amp charger can do it, but you are looking at a long time to charge.

Before I upgraded to a bigger TM, I had a 12 volt system with two batts in parallel. It made a huge difference in my case going from one batt to two in parallel. W2S is right on with the answer on charging. Give em a good hot charge right after use.

I encountered this issue years ago with my previous boat, so here's what I did. I was fishing 150 to 300 or so acre conservation lakes and I was concerned about running out of batteries so I got 3 deep cycle batteries and ran them in parallel. I solved the charging issue by getting a 3 bank charger (it was supposed to be an on board charger) I didn't install it in the boat, I just kept it in my garage and once I got home I'd wire it up to all 3 batteries (which took less than5 minutes) and just plug it in and leave it. I had other issues with that boat, but I never ran out of battery power.

I also got new batteries every other year.