Bad Battery or Alternator?

[carbonM]

I get the battery discharge warning every now and again right when starting the car or turning the car off. Never have gotten it while driving.

I put a meter on the battery connections under the hood while the ignition is off and I get 11.7v. Switch the ignition on, it drops a bit to 11.4v. Turn on the engine and I get roughly 14.4-5v.

Seems like it would be a battery issue? Shouldn't the voltage be 12.4-5v when ignition is off?

[bandwagn]

How old is the battery? They are known to go through batteries every 3-4 years

[carbonM]

Looks like it was replaced back in June 2013.

[Naz24]

Originally Posted by carbonM

Looks like it was replaced back in June 2013.

You'll probably need a new battery.

You may be able to extend the life a bit by hooking up a ctek battery tender and charging it. see what happens

[Thecastle]

11.7v is an extreme state of discharge. Car batteries are often damaged by that low of voltage.

I’d replace it since it’s an auto battery and discharging it below 50% aka about 12v ussally damages them.

[carbonM]

Here is a picture of the battery label, which says 92ah. Most of the batteries I see at local auto stores are 95ah, so I assume I would need to register a new battery.

[grayghost11]

I also get that message every so often. Hooked it up to standard battery tender and it usually solves the problem.

[philly42]

The proper way to do this test is with a lot of electrical load.

Turn on the car and switch on as many electrical items as possible. essentially inducing a heavy electrical load.

-Max AC
-Heated seats (front/rear)
-Vented seat/active seat
-High Beam
-wipers
-Radio

Then check your volt meter. If you see the voltage starts dropping below 13v, you might have an issue with your alternator or voltage regulator.

[Thecastle]

Originally Posted by carbonM

Here is a picture of the battery label, which says 92ah. Most of the batteries I see at local auto stores are 95ah, so I assume I would need to register a new battery.

Whenever you change the battery you should register it. It’s resertting the charging scheme on a bmw to account for the fact the battery is new.

But like I said, you have an automotive battery not a deep discharge battery. Automotive batteries have very thin/high surface area led plates which are great for short bursts of high current for starting. However the plates are easilty damaged when the battery is more than 50% discharged. Your battery has been deeply discharged and will likely need replacement

Just go to autozone and have them do a battery and alternator load test. They do it for free, and will tell you exactly what’s wrong.

[RichardR0404]

These batteries arent build to last anyway..... battery lprobably dead already. Mine went through 3 batteries already, its a 2013 model so...