Killing batteries

[vforge]

Hello, we have a M939 with the original battery setup. Recently, we found one of the batteries was not getting fully charged. Cell levels were fine in it. I put it on a charger, it wouldn’t charge to 100%. We drove it around and I checked the voltage and the battery was low. Just that one battery, the rest were fine. I decided to try keeping them all on a maintainer to keep them evenly charged but the one just wouldn’t hold a full charge.

We decided to replace it with a fresh battery a few days ago. Now the same thing is happening to another battery in the group. I got a battery load tester, I had it on the charger till 90%. Battery tester shows the voltage dropping and CCA was 480 (rated 875, others tested 1100).

 

[NDT]

End of life? Are you running 6TLs?

 

[vforge]

End of life? Are you running 6TLs?

Yes. Batteries are only 2 years old.

 

[NDT]

Ya gotta use maintainers with these or 2 years is about it. Most of us are going to group 31s. Some of us are going to group 31 AGMs, with a maintainer, those can last 6-8 years.

 

[SCM35A2]

It's been suggested, but run the group 31 batteries & you'll only have to use two of them. I swapped them into my truck right after I got it & that's been 4 plus years ago.

 

[vforge]

I'll probably go the group 31 route then. A group 31 AGM is the same price as a 6TL. I'll make the switch as soon as another one of these batteries start giving me trouble.