Charging Batteries, 3 of Them

[Moss Man]

My Peterbilt 378 has three batteries and at least one of them has gone bad. I don't use it on the road right now, but when I go to start the ole girl it's a no go. I boosted it yesterday and it fired up. Ran it for 20 minutes, shut it off and it went again. Today, she no go again. Pulled every terminal off and cleaned them all, battery end and starter end. Also cleaned the ground to frame wire.

I tested the voltage at the batteries with them all hooked up and got 10.65 volts, not good.

Two questions.
1. How do you tell which or how many are bad?

2. Is it OK to charge all 3 at the same time with all the terminals hooked up?

 

[hanniedog]

You need a battery tester in order to find the bad one. You will need to disconnect all the cables to check each individual battery. Yes you can charge all three at one time.

 

[Moss Man]

Hello,
Could you have a slow leak? If it started back up after a short while, the batteries may not be bad, just slowly losing their charge. Just a thought. Thanks.

I tested all three batteries after they had charged overnight, one was 10.7 volts. I removed that one and it starts well on the 2 good ones, at least while warm weather holds out.

 

[Oly's Stump]

Buy a good tester. Get one with a switch to put a 10 second load on it.

 

[ShoerFast]

Best test I know of uses a volt meter , your engine and starter, tested while cranking.

Fully charge the batteries

Pull the fuel-stop or disable the injectors (kill switch) and crank it for 15 seconds testing each battery +post ~ -post.

Good batteries hold 9.6V or higher for 15 seconds while cranking, those that have bellied up will drop like flies, most of the time you do not even need to crank for the 15 seconds.

 

[CalTreeEquip]

Good advise.

All good advise above.
I would want to determine the age of all he batteries and they're life span.
If they were all bought at the same time and they're close to they're life span, then replace them all. Other wise, if you replace just one the older ones will over work the new one as they get weaker, next month.
Also check the fluid levels and specific gravity, that will tell you if one can hold a charge or not.
I usually just pull the batteries out, charge them up, test them, let them sit for 24 hours and test them again. If they won't hold a charge you know. Testing under a load is just as good. Just make sure there is water in them.

WWW.CALIFORNIATREEEQUIPEMENT.COM

 

[380LGR]

Is it worth 300 bucks for the truck to start when you want it to?? If so go get new batts if not keep torturing yourself.

 

[Moss Man]

Is it worth 300 bucks for the truck to start when you want it to?? If so go get new batts if not keep torturing yourself.

Torturing myself? We have varying opinions on torture!

The two good batteries tested very well and start the truck so well the third won't be needed till cold weather sets in. The bad battery was all the way down to 10.7 volts after a 24 hour charge was applied....junk.

I don't believe the two good batteries are going to have much affect on the new one when I install it.

Tossing $300. at a problem that can be solved with $100. seems a bit of a waste to me. Perhaps I will eat those words when I am 300 miles from home and the sucker won't start!

 

[380LGR]

Once one goes the others arent far behind on all my equip with 2 or more batts i change them all out when one goes bad.