Why does my '08 Impala SS eat batteries every 2 years?

[Bminder]

Back in 2010 I bought an '08 Chevy Impala SS with the 5.3 V8.  An extremely fast car with an extremely crappy suspension, steering feel, throttle body, transmission, body, paint job, sound deadening... I wish I hadn't bought it.

But anyhow every two years since it was new, the oem AC/Delco battery goes bad.  Since the battery is always still under warranty, I keep getting a free AC/Delco to replace it. But two years later, it starts to crank slow when starting and then one day will be dead.  The parts store puts their testing machine on it, it says the charging system is functioning normally, it's just the battery going bad.  It's  now on battery #4.
Anyone ever had this problem?
I'm wondering if the charging system is overcharging the batteries and slowly killing them or something.
Any ideas?

[TexasDave]

How often do you drive it?   Dave

[Bminder]

Every day. My wife drives it the most.

[the fan]

Aftermarket radio or alarm?

Sounds like there is a small but constant draw on the system. Had this problem on a van I used for hauling bikes and the combination of the alarm and the power source for the sterio memory would draw on the battery causing premature failure.

[TexasDave]

It could be a loose or corroded ground and thats the first thing I would check. With a bad ground you can still show the battery getting the required voltage off the alternater but not enough amps to fully charge the battery. Been there done that.  Dave

[TexasDave]

Aftermarket radio or alarm?

Sounds like there is a small but constant draw on the system. Had this problem on a van I used for hauling bikes and the combination of the alarm and the power source for the sterio memory would draw on the battery causing premature failure.

Yes--have seen this on an aftermarket alarm system also.  Dave

[FJ_Hooligan]

Either keep with the "free new battery every 2 years" plan or try switching to a different battery.

If you drive it every day and don't notice any slow discharge (like cranking slowly first start every morning) then maybe the batteries really are just going bad.  No telling who really makes the AC/Delco batteries (probably a chinese low bidder).

[TexasDave]

Lead acid batteries work pretty well as long as they are kept charged up. If they are not kept fully charged the ph level falls and the lead plates start developing lead oxide. A lead acid battery will discharge at a rate of 1 1/2% a DAY just sitting on the shelf. Yours is not getting a full charge or has a larger than normal draw on it when it is not running. If she just drives short distances the battery might not have a chance to fully charge. You could put a charger on it every couple weeks.  Dave

[Bminder]

All stock.
I'll try cleaning all the grounds I can find.
I wondered if it's overcharging it.

[Dads_FJ]

I had the same issue and the issue was the same as "the fan", a slow current draw on the system (it was an aftermarket phone accessory.  Measure the current draw when the car is off, I'm sure there's a spec for it. Could be as simple as a trunk or hood light not turning off.

[Earl Svorks]

  Hi Bminder,
Battery issues, I've had a bit of experience there.
I think that any sort of hidden key off draw will show up in a short time and leave your battery discharged in the same time frame every time. A simple recharge and you're good until the next cycle, or until you locate and repair the grief. This is a matter of typically a couple of days, or a week.
Your battery is not just becoming discharged, it's dying and will not take a charge (if I understand
your post correctly) We used to call this "Taxi Batteryitus" when I wrenched with Yellow Cab.
I went all the way to the battery manufacturer looking for the answer to this. What I learned from them  served me well over the years following .That being,,, the battery will live longer in a cooler
environment.The temperature under the hood can go way past what's best for the battery.
Your particular geography doesn't have the coolest of weather, this probably doesn't help.
Put the battery in the trunk, customize some welding cables,,,
  This isn't too long,, is it?