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Both Batteries went bad at the same time?
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Author:  J_6961 [ Mon Apr 09, 2012 12:21 pm ]
Post subject:  Both Batteries went bad at the same time?

A few weeks ago the car seemed to labor when I hit the starter button. The two, 1000A batteries were about three years old. I decided to put new ones in and I was lucky enough to get a full warranty on the existing ones, so that was great. Put the new ones in and they immediately spun the motor like they used to. Last Friday, I put the charger on them to make sure they were up before the Saturday, TnT. Saturday morning, at the track, I hit the starter and they acted like they were very low, barely turned the motor over. When I hooked up the booster cables from the truck to the car, I could hear the truck motor laboring immediately. When I hit the started with the cables attached it spun the motor as usual. Even after charging the batteries at the track, if the car sat for more than 10 minutes without a charger on it, they would not turn the motor over.

I’ll go ahead and replace both new batteries again, but it seems odd that both brand new batteries where bad. Could there be something else causing this?
The setup is old school, two 1000A liquid cell batteries with no charging system on the car. I just charge them after I get back to the pit. Batteries are Costco brand, and I've always had good luck with their batteries.

Author:  Ken0069 [ Mon Apr 09, 2012 1:53 pm ]
Post subject:  Re: Both Batteries went bad at the same time?

Alternator!

I know you probably don't want to hear that, but I started running one way back around 1990 and I'll never go back to running without one.

I also have a charging system in the trailer, ie, it runs off the truck charging system back through the trailer plug and it will charge the battery going to and from the track.

That Camaro I just sold had one battery mounted crossways in the trunk. It was a Duralast and was in that car when I bought it in 2006 and I last ran that car last August of 2011 and it was fine then. It showed 12.7 volts when the guy that bought it came and looked at the car back in January.

As for draining two that quickly, dunno but I'd bet there's a current drain there somewhere and that may even be inside the battery. Cut EVERYTHING off, then remove and replace the negative cable to see if you get a spark. That or you could connect an amp meter between the positive post and that clamp just to make sure that there's nothing drawing current when it's suppose to be off.

So how are these batteries mounted, ie, posts side to side or inline with the direction the car travels? :-k

Author:  J_6961 [ Mon Apr 09, 2012 2:29 pm ]
Post subject:  Re: Both Batteries went bad at the same time?

Yes ... an alternator is on my to-do list. =; The batteries are mounted correctly so the plates don't bump into each other, but these new ones haven't even made a run yet. Just a couple warm-up cycles in the driveway.

Author:  rick360 [ Mon Apr 09, 2012 5:05 pm ]
Post subject:  Re: Both Batteries went bad at the same time?

Makes me wonder if you have a bad connection??? Have you tried a single known good battery by itself?
I'd also do like Ken suggested measuring current draw.

Rick

Author:  Beretta [ Mon Apr 09, 2012 5:43 pm ]
Post subject:  Re: Both Batteries went bad at the same time?

GROUNDS!!!!!!!!!!!!!!!!!! Does the engine have a dedicated ground to the Battery???
You may have a draw issue but grounds are usually an issue..

Author:  gearhead1011 [ Mon Apr 09, 2012 9:06 pm ]
Post subject:  Re: Both Batteries went bad at the same time?

If one of the new batteries is bad it could drain the other good one. Measure current draw and charge and separate the batteries then let them stand for a couple of days. If one dies and the other still checks good you've found the problem.

Author:  J_6961 [ Tue Apr 10, 2012 12:07 am ]
Post subject:  Re: Both Batteries went bad at the same time?

I'll go and check all my connections another time to be sure.

Motor/block does have a proper ground back to the same ground cables the batteries are connected to.

I have not separated the two batteries, so I'll try that as well.

The only thing different from last year was adding a relay to the new fuel pump. Could a relay somehow draw down the batteries?

Thanks for the help! \:D/

Author:  J_6961 [ Wed Apr 11, 2012 11:19 pm ]
Post subject:  Re: Both Batteries went bad at the same time?

Quick update ... Charged the batteries separately and let them sit for a day or so. Tested them tonight, 12.64 & 12.61

Next up is to load test each and then we'll see.

Author:  J_6961 [ Sun Apr 15, 2012 8:12 pm ]
Post subject:  Re: Both Batteries went bad at the same time?

OK, so one of them was a bit low on the load test, but I wasn't sure. So, exchanged both anyway and installed two new batteries. I also spent the day redoing all the grounds on the car. Front to back there was a total of just under 5 ohms.

Hooked it all up and everything works good. Looking forward to next weekend if the weather cooperates.

Author:  ADAMSVEGA [ Fri Sep 14, 2012 8:56 am ]
Post subject:  Re: Both Batteries went bad at the same time?

you need to find the draw on system . put a test lite from neg. cable to battery disconected .if it lites up you have a draw. no pull each fuse and hardwired load off one at a time till you see lite go out ....fix that circuit. had a sticking relay on trans fan do this

Author:  SGDCXCVI [ Sat Sep 29, 2012 7:21 pm ]
Post subject:  Re: Both Batteries went bad at the same time?

I found this info on Bracket Talk. Might help. Make sure you watch all 4 episodes.
http://www.youtube.com/watch?v=4f-vWFOY ... ure=relmfu
Cheers Colin

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