Series Battery Replay

[johnboat]

Two Interstate 27's in a series for a trolling motor, 24 volt. They have always been together. Same charge and run time, stored together, same everything. One goes bad, won't complete a charge. Other one is perfect. All cells test at 100%.

The battery that went bad was connected to the positive on my trolling motor.

I had the same thing happen 3 years ago.

One went bad, the other perfect. Again, the one that went bad was connected to the positive on my trolling motor.

Coincidence, or does the positive terminal battery take more of a beating?

JohnB.O.A.T.

[ffishman]

Something sounds amiss. You have to make sure it is wired correctly. Put the trolling motor on low and on off. Remove each lead one at a time and put a test lamp inbetween. Turn the trolling motor on and check the reading. The draw should match from each battery. If you take one lead off and try the motor, and it works, then it is just operating off 1 battery.

[Hawker]

It sounds coincidental, somewhat amiss, but coincidental nonetheless! When you say all cells test 100%, may I ask in what manner the cells were tested?? A load test (after batteries are as fully charged as possible) will give you an overall performance evaluation of each battery, but to test each cell individually and correctly, a "specific gravity" test of each cell is the best test to run! (not with a cheap floating ball tester)

In regards to your series jumper from positive to negative, is that jumper at least a 6 gauge jumper?? I'd recommend a #4 myself, but that's just my personal choice! Do you happen to have any 12 volt accessories (radio, locator, lights etc) connected to either battery? Are you using an onboard charger or two seperate 12 volt chargers? What size charger(s)? Kind of a perplexing situation I know, but the more information you can provide we might be able to be of some help!!

[johnboat]

Yes I'm using 4 guage. The trolling motor is hooked up right, and has always worked fine. Both batteries have always been charged on the same Minnkota on board charger, and no other electronics are hooked up to these batteries. 3 years is what I expect to get out of my batteries, so it's no big deal. But since the same battery (#2) in the series went bad, as before, I was just wodering If the positive charge side of a series took more of a beating. I'm leaning to coincidence myself. And yes just using a cheapo ball floater for testing.

[Hawker]

I can't help but think coincidence that it was the same battery both times! In a series connection, your only doing externally with a jumper, what each battery does internally! I'd be curious to know if you had only one cell in the second battery go bad, or if they all deteriorated at much the same rate if you happen to know! I too (just a month ago) had to replace batteries but instead of two, it was four! I also run a 24 V TM and as a guide have to rely heavily on my TM to perform. I parallel battery one & two, parallel battery 3 & 4, then series those two banks to get my 24 volts. I had both batteries on the negative TM connection side go bad on me, but the other two were still showing near 100% of life so relegated them to bait tank air pump & recirculating/filter pump service, and for running all my electronics respectively! The last set of batteries were 27 series batteries and I jumped on up to series 29 and thus far all is working fine.

I'm wondering if maybe one side of your onboard charger is possibly overcharging the battery in question? I too run MinnKota onboard chargers (two 3 bank) and have notice when checking with a voltmeter while charging that one bank will be charging at a higher voltage than the other two, or visa versa the times I've checked! This last time that I replaced the batteries, I switched the battery charger leads around just to see if that made any difference, only time will tell!

[Hot Runr Guy]

maybe that bank of the MinnKota charger is a little flakey?

HRG

[haybay larry]

At the ned of each season why not rotate the battery position around. This would even out any possible issues with one of them charging differently. It may also extend the life of your batteries.

[johnboat]

Originally Posted by haybay larry

At the ned of each season why not rotate the battery position around. This would even out any possible issues with one of them charging differently. It may also extend the life of your batteries.

That makes WAY to much sense. No wonder I never thought of doing that.......................untill next season!

Thanks for the tip!

[JAK]

Originally Posted by johnboat

That makes WAY to much sense. No wonder I never thought of doing that.......................untill next season!

Thanks for the tip!

I was thinking the same thing about one bank of the charger being bad. However, I wouldn't change the battery around ...I would just switch the charger leads.

[Paul H]

30+ years ago, Delco had those "eye" that showed if water was low. We were instructed to always place om the 2nd cell from the positive, they said it was the 1st to go low, 1st to go bad.