AGM Battery problem

[mustang50lx]

I bought a Braille Absorbed glass mat (AGM) light weight battery for my car. It seems to lose voltage as I drive. When I got it it was low so I charged with my regular battery charger. It would only charge to around 80%. I bought a Shumacher battery charger that would properly charge an AGM battery. It charged to 100% and still the same problem. The battery will be around 12.9 volts when I leave for the track. It will be 12.7 when I get there and 12.6 after 2 passes. I just charge it at the track but this can't be right. I also sent the original battery back and got another one from Jegs. Nothing changed. The alternator is putting out the right voltage, but I didn't load it to check the amp output. I had no problem with the old battery at all.

[Balaska347]

Is it a stock alternator or a 3G? And do you know what amp alt it is?

[Martin0660]

If you have a 3G alternator, they will die fast if connected to a battery low on charge. They overload with a big recharge rate cold.

Also AGM batteries do not like to be charged by the car if low on volts. Add the 3G issues to the AGM issues, and a low battery will kill one or the other. It was said, it is like a lightning storm inside the battery if cranking when low on volts, then the charge circuit turns on.

Also, starting a car on a low AGM really beats it up. I was told that if you use the car to charge the battery from a discharge state, it substantially shortens the life of the battery. Although they are designed to be deep cycled a lot, not three step charging them would shorten that to something like 10 cycles.

I've never heard a single good thing about the Braille batteries FWIW. I've got very good service from my Oddysee, with the only failure being when my voltage regulator stuck high and cooked it to death (20+ volts). I deep cycle mine a lot running my fan, but always watch the volts before starting the car.

[Balaska347]

I ran a similar battery for about four years and it was more hassle then it was worth. I threw it in the trash and put a regular battery in.

[mustang50lx]

It's still a regular stock alternator. I was looking at Oddysey Batteries, but I was a little concerned about using one with a V-8. I try to keep it charged between rounds. I might send it back and put the regular one back in. IDK. I'm kinda POed that I drilled a bunch of holes and rerouted wiring and now I may not be able to use it.

[Balaska347]

I think the stock alt is your biggest problem. My stock alt wasn't enough for my car once I put the pulleys on.

[SK@StreetLethal]

Oddysey makes batteries in all sizes. We've installed them in quite a few cars with no issues.

[mustang50lx]

I think the stock alt is your biggest problem. My stock alt wasn't enough for my car once I put the pulleys on.

I was wondering if the underdrive pulleys were a problem.

[pRojekt02GT]

Had a charging issue in my old 02 GT after I installed UDP's. Ate up the battery quickly, never figured it out afterwards..dawned on me that it was probably the alt.

[Balaska347]

I had to put a 3G 130 amp on mine

[mustang50lx]

I had to put a 3G 130 amp on mine

Did that totally solve the the problem? Where you still running an AGM battery at that time?

[Balaska347]

Not really, it just didnt hold a charge well. I now run a red top optima which I have no problems with.

[mustang50lx]

The underdrive pulleys seem to have been the problem. The battery held a full charge all day yesterday while driving to the track and racing. The water temperature also stayed alot flatter or smoother. With the UDP's the gauge would float around alot. Now it is steady. I only lost a couple hundreds in the 1/4 if anything too. No more UDP's for me. With that said I have a nice set of Steeda UDP's for sale. Probably didn't give the best sales pitch ever. Kinda like one of those "truth" cigarette comercials.:D