Ernesto13B

iTrader: (4)

I bought a Diehard Platinum battery about 2 months ago, and I look and noticed acid all over the top of the battery. I didn't even think AGM battery's could leak acid but I guess I was wrong. The car starts fine and drives ok but what the hell is up with the acid??

I thought my freshly rebuilt alternator might be overcharging, so I checked the voltage and got 14.3-14.4 volts at idle, and increased the Rpm and the maximum voltage I got was 14.6, because I believe that's what its regulated at. Last time I checked 14.6 volts max was not considered overcharging but are AGM batteries more sensitive??

My question is... is my alternator REALLY overcharging??? or is the DieHard platinum battery too sensitive and should I just go with the good old fashion DieHard Gold?

KaiFD3S

iTrader: (37)

The battery may be defective, just go back to where you bought it and replace it if you just bought it, the acid will eat your car up...

Be carefull not to get it on your clothes as it will eat it too..

Ernesto13B

iTrader: (4)

I already returned the battery today and got a new one but im scared that the problem might come back.

My old conventional acid battery was in my car for 3 months before I replaced it, and I replaced that because the car started having slow cranking, NOT because of acid leaking, that battery never leaked acid even with my rebuilt alternator installed in the car

Does anybody consider 14.6 volts to be overcharging?

94touringFD

iTrader: (30)

The gold will work just fine, that's what I have. Just take it back to sears and get another one. Tell them what happened and that if it happens again you would like to downgrade to the gold. They shouldn't give you a problem. I'm a sales associate at sears auto myself so I can tell you I wouldn't give you a problem if you were a customer at my store, and not just cause you're a fellow FD owner, lol.

I know we sell a special charger for AGM batteries but platinum series should work just fine with a new alt.

DaveW

Here's some battery info that should be useful:

http://www.windsun.com/Batteries/Battery_FAQ.htm

And, no, 14.6 volts is NOT overcharging. I have a DEKA ETX18L AGM battery on my racecar, and during the "equalizing" (brings all 6 cells to maximum charge) charge phase, the Schumacher "SpeedCharge" charger puts out as much as 15.8 volts, and I do not lose any acid.

DaveW

BTW, this assumes that the battery in question is not a Gelcell battery, which cannot stand as much charging amperage or voltage as the other battery types.

Dave

Ernesto13B

iTrader: (4)

No the battery is not a Gell Cell, it is an AGM, so I don't know how leaking is even possible. It started spewing out acid out of the vent hole and started making a mess.

DaveW

AGM's are also called VRLA (valve regulated lead acid). If too much voltage/amperage is applied, the valve, which is there to prevent the battery from exploding, releases pressure from outgassing caused by the too-rapid charging. This carries some acid with it and results in what you are seeing.

I suppose that even tho you said you only see 14.6 V, that the voltage/amperage is not reducing (faulty regulator?) when the battery is fully charged, thus giving you the problem. It could also be possible that the battery has a bad cell, which results in overcharging the remaining five cells.

Dave

Ernesto13B

iTrader: (4)

I just found my rebuilt alternator's bench test paperwork. It says the maximum set point for the voltage regulator is 14.7 volts and maximum Amperage is 121 amps @ 5000 rpm.

In real world figures on an actual car with all the loads these number come out to a little less, which is why I only got 14.6 max. Im gonna do some more testing, but from all the tests that iv'e done so far, at idle, voltage is 14.3-14.4 and as I increase it goes to 14.5 and hovers around there, but I couldn't get it to go past 14.6 volts

Ernesto13B

iTrader: (4)

Im pretty sure im overcharging, because I checked it again just now and I got 14.6 at idle, and I got 14.75 at higher rpm, and I think thats a little too high. Im pissed that I thought I had a good rebuild but I guess not. I just gonna have to buy a new Mazda OEM alternator. Also my battery has about 13.10 volts when the engine is not running, and that I know is NOT normal. Life sucks but I gotta do what I gotta do

DaveW

Actually, seeing a bit over 13V just after charging is not unusual, because a "surface charge" builds up during the charging process and dissipates over a few hours after charging is stopped.

However, having said that, there is something wrong if the battery is blowing acid out the vent, so hopefully, the new alternator will fix that.

Dave

Ernesto13B

iTrader: (4)

I really don't feel like spending $200 on another alternator, and then having to install it again, so what im gonna do is have the money for that saved just in case the problem comes back.

After doing a lot of research, supposedly AGM batteries can handle higher charges then wet cell batteries, and most people say that it's normal for the alternator to charge in the 13-15 volt range as long as it doesn't go over or below. I will keep an eye on my battery, but i'll have the money saved for the alternator just in case, this is just VERY frustrating.

My previous battery (had it for 2 years) was a wet cell diehard Gold, it lasted me 3 months with my rebuilt alternator then ONCE it gave me slow cranking. I decided to replace it just to be safe, even though the car still started fine. That battery never leaked!! this is why im so confused. Thanks for all the help i'll just take it step by step.

Ernesto13B

iTrader: (4)

There is something I didn't realize until now. IF my alternator is overcharging my battery, it should still be in warranty from the place I got the rebuild from. The warranty is one year if I remember correctly.

I checked the factory manual and according to what it says, the voltage is normal if it's anywhere from 14.1-14.7, so I don't know why im having a problem.

My voltage regulator set point is 14.7 volts which may be too high. Wouldn't I simply be able to replace the voltage regulator with another one with a lower set point like for example: 14.2 volts?