I made a critical mistake last year, I purchased a 12 volt trolling motor(was a heck of a deal). I have 2 brand new batteries under my bow that I use for my trolling motor. I was wondering, would it be better to use these batteries independently or shoudl i run them in parallel. I have them hooked to a two bank onboard charger, if that makes a difference. One more question, I have two used batteries that came with my boat (two years old) either I or the previous owner forgot to top off the water level and it appears that there is corrosion on the battery plates. Is there a way to "rejuvinate" these batteries.

Thanks for the help and good luck to all.

I just got a rig at Northern Tool for $50 that is supposed to rejuvenate a battery. Check out Model# 12117 You have to put it on to charge the battery up and then it goes into some mode that pulses and that's supposed to clean off the plates. I am only on day 3 so I can't say how well it does the job.

I don't think you gain by going parallel. You get twice the amount of time but you still have to charge them both up. If you stayed with one at a time you could switch them out and never be out of luck.

You can learn a lot about batteries by googling "deep cycle batteries" the first thing that comes up has a number of answers to FAQ's

You should never charge two batteries that are hooked up in parallel. Your charger will be getting false signals, it may not be fully charging your batteries and/or it may over charge them. You'll have big problem. If you do run the batteries in parallel, disconnect the wire that parallels them before charghing.

I have a Vector Charger from Northern Tool. It has a "recondition" mode that pulse charges the battery over a 24 hour cycle and it breaks up the deposits on the plates of the battery. I've used it to bring two old deep cycles that my wife's ex husband left in the garage back to accepting full charges. They had been sitting in the garage for about 2 years and would only take about a quarter charge when I started. I recommend it.

Did she get those batteries as part of the divorce or are you going to have the case reopened now that those batteries are working again? Don't want to cheat the guy, do you?

That's interesting. I don't fully understand why your charger would have a hard time with this. With both in parallel, both would draw current as they can or need. Once fully charged, the one with lesser charge will draw most of the available current. Are you suggesting that the other one may get overcharged as a result?

Bob

Really, it's all the same in the end.

Use one at a time, or both in parallel, the amount of total A/hr available is basically the same.

EDIT: Actually, you'll probably get more time running the two batteries in parallel. This is because the total amount of power one can draw from batteries depends in part on how fast the power is withdrawn. So, with the batteries in parallel, each is discharged more slowly, thus will give up more total power.

The charger has indepent banks which monitors current resistance. When batteries are hooked in parallel, they become like one battery with a longer reserve run time. When a two bank charger is hooked up to each battery as supposed to, it is like taking the two positive ends of the bank wires and connecting them together because of the parallel wiring. The charger will stop charging whenever one battery reaches full. This will leave the not fully charge battery undercharge. The charger reads off the highest current feedback. The current feedback from the lesser charged battery goes unnoticed by the charger because it's current feedback is less than the full battery's feedback current.

I hope that makes sense.

I picked up one of those battery minder rejuvenator things from Northern. First week I tried it - no gain in battery capacity, so I hooked it up for another week....again, nothing happening to "rejuvenate". Not sure if I need to leave it on for a long time, or what, but so far it hasn't been working for me. The battery load tests ok and charges ok....just doesn't last long at all. If I had to do it again, I'd save my $50 and spend it on another battery!

I've got my Vector hooked up to a deep cycle right now. I'm in week two and having the same kind of luck as you. No tangible improvement to the battery at all.

Perhaps your battery problems aren't related to sulphation...