12/24 Volt System & Batteries

Okay all you electrical/battery gurus, I have a couple of questions. I have a 67 lb thrust trolling motor on a standard 12/24 volt set up. I am starting to have some trouble. Probably a bad cell, but I want some input before buying new batteries again. Lately fishing in windy conditions where I have been using the tm alot, I am running down one of the batteries totally. The last time was this past Sunday in only a few hours. When I switch over to 24 volt I have power again. Shouldn't both batteries run down somewhat equally during use since they are wired together? When I switch to 24 volt am I simply switching over to the other battery since I again have power? I do notice when I do so that the tm isn't as strong on 24 v as normal. Is this problem as simple as a bad battery or should I be checking other things as well? I put the batteries on charge as soon as I return and they stay charged via my on-board charger. If it is time for new batteries I will probably go with Optima this time. Who/where has the best deal on the blue tops as well as one for cranking (yellow top?)?

Thanks.

What happens if you start on 24v? If the batteries go down at about the same rate you don't have a problem. If just the one does you likely have a bad battery.My boat is set up so on 12v it just runs the one battery and then if you go to 24v the other kicks in. I usually just leave it in 24v and run lower speeds when I don't need extra power. I'm no expert but hope it helps.

Always run a 12/24 system on 24 volt. This will discharge both batteries at the same rate. JMO...

Crankin's on the money, a 12/24 TM runs off one batt in 12V mode. When you switch it into 24V both batts are in series, so you're using the combined voltage of both. My TM is a 24V, but when I had a 12/24 I always just ran it in 24 mode and used the thrust control at the pedal. In 24, both batts discharge and wear evenly, and should easily last thru a whole day's fishing. The only time my old 12/24 would weaken was after a long day of crankbaits, or maybe fishing ledges on a windy day.

If you don't have a temperatur compensated refractometer to check your electrolyte you can check each individual cell with a multimeter. Just take the cap off the cell and place the red lead in the cell electrolyte and the black lead on the ground terminal and read the voltage from each individual cell each should read about 2 volts DC. If you find one that is reading much lower it is the bad one.