Battery low warning sign on dash even after new battery?

[pablom2c]

Hi,

I have a 2008 135i which I think still had the original battery, I have owned the car for around 2 years now and it only has 35,000 miles. Anyways since I bought the car when I stop to fill gasoline it would show on the dash the battery low warning sign and cut the power, and the angel eyes and rear lights would stop illuminating when unlocking the car for example, but the battery never got low enough to the point of losing the time or other functions (I have read in other threads that this happens when battery is extremely low). I used to put a battery charger every month and these symptoms would get fixed temporarily for a week or two and then come back again.

Recently I replaced the battery with a new one and programmed it with Carly BMW app, and I still have the same problem with the same symptoms. I never leave my car unlocked and I don't have any modifications or devices plugged in draining the battery. If I charge this new battery the charger tells me it is at like 95% and reaches 100% very quickly, so it doesn't seem to be really low? After charging everything works fine, and in less than a week the symptoms come back. I do drive short routes everyday of around 15 minutes to and from work, but this has never happened with other cars I've owned doing the same. Also why does it discharge so fast if I keep charging it anyways. The only time I leave the car unlocked is when washing it but only when cleaning the interior which would take me 10 to 15 minutes, later when I wash the outside I lock it again to avoid draining the battery.

Is this related to the battery cable recall in the glovebox in any way? Unfortunately in my country they don't do recalls like in the US so I guess this was never done on my car.

What else could be the problem? Is this caused by bad programming of the battery? Should I try again with the Carly app even if the battery is a few months old now?

Thanks a lot.

[kprocivic]

Maybe sounds like the alternator.

[pablom2c]

By the way the battery I bought is a BOSCH S5 Mega Power.

Should I get any codes for the alternator?

[kprocivic]

I didn't, and if I remember correctly mine went out when the battery went out.

[Mr Gasser]

When the car is running hook up a volt meter. It should read 13 to 14 volts...indicating that the alternator is charging. If it is at 12 or even less, its shot.

[chris_flies]

My alternator makes an annoying whine. My less-than-knowledgeable friend asked if it was a supercharger. But, it still charges fine.

[02Pilot]

There should be fault codes stored if the battery charge state is low. You should also be able to read the battery charge state over the past several days via the car's own computer. When you registered the new battery, did you check for and clear any fault codes?

That said, running for an extended period of time with a bad battery is a really good way to kill an alternator. If the battery is not charging properly, replace it immediately.

[Matticus91]

Originally Posted by kprocivic

Maybe sounds like the alternator.

Originally Posted by Mr Gasser

When the car is running hook up a volt meter. It should read 13 to 14 volts...indicating that the alternator is charging. If it is at 12 or even less, its shot.

+1 to both these guys it sounds more like the alternator to me. If the battery is new and it's not holding a charge even on basic functions then either the battery is a dud or there's something going on with the electrical system. An alternator failing on an 08 makes sense to me. Just check the voltage like Mr Gasser said or bring it to any shop and they can do that for you, likely for free since it would take literally one minute.

Originally Posted by 02Pilot

There should be fault codes stored if the battery charge state is low. You should also be able to read the battery charge state over the past several days via the car's own computer. When you registered the new battery, did you check for and clear any fault codes?

That said, running for an extended period of time with a bad battery is a really good way to kill an alternator. If the battery is not charging properly, replace it immediately.

Not necessarily, these cars get weird with low voltage. I had the alternator go bad on my first 1er and nothing ever showed in the system. On my second 1 the battery was toast but the car didn't display any warnings until it was at an extreme point - where it was a gamble getting it to start after sitting for 5 minutes stopping from a 2hr trip.

[pablom2c]

Thanks a lot for your comments guys, I will get it checked following your advice.

[Dackelone]

Do you have access to a VOM(Volt/Ohm Meter) ?

With the engine running... you should have at least 13.4 volts DC volts across the battery terminals in the trunk.

With the engine OFF your battery voltage should be at least 12.8 with a fully charged battery. Nothing lower than 12 dc volts - or your battery is not holding a charge.

With the engine running... check to see how many AC volts you have across the battery terminals(plus and minus)... anything more than 1 AC volt and your alternator is shot.

With some LONG test leads... measure DC volts from the NEG battery post in the trunk and with the other test lead put it on the engine somewhere that's grounded. Start the engine and have an assistant check for peak voltage. ANYTHING more than 1 DC volt and you have a ground issue.

Also checking for ohms with the engine off... measure the ohms from the neg battery post to the chassis in the trunk area. You should not have more than ONE ohm. Really you should have no ohms... ie direct contact - zero ohms.

Make sure your battery cables are good and tight. Especially the negative cable at both ends where the other end attaches to the body/trunk of the car. Try to wiggle the cables... there should be no movement. Also you should have no corrosion at the battery terminals.


Can you have the shop who sold you the new battery "load test" it ? Just because a part is new doesn't mean it is a GOOD part. No telling how old that "new" battery is or how long it sat on the parts shelf.


Maybe this video might help you out...

[pablom2c]

Wow thanks for the detailed reply, will get the shop to check next week as I don’t have the tools.

What I tried tonight using an OBD adapter with the OBD Command app says the battery is at 13.6v with the engine running. I also connected a battery charger and it read 12.5v with the engine off but the charge is at 74% only.

[pablom2c]

Just went to check the charger and in less than 10 minutes it went up from 74% to 90%? This doesn’t seem right? With my old battery that would take hours not minutes or did that happen because the old battery was definately bad?

[02Pilot]

You're likely just reading surface charge. Do the multimeter test and see what it shows with the engine off after letting it sit overnight, or alternatively after running the headlights for five minutes with the engine off. You have to remove the surface charge from the battery to get an accurate reading.

If you can, get plugged into a proper BMW scan tool and check the battery charge state over the last few days.

[NorthernDancer]

Buy a DVM like in Dack's video. They're dirt cheap. And learn how to use it. Otherwise, you'll be into the shop often and paying huge amounts of money.

[Mr Gasser]

Having a good alternator will ensure the battery will last a loooong time too.