[jknight]

Back story: So a few days ago I got a message from my car one morning that there was excessive drain on the battery and that if this message continued to see the dealership. Well, the next few days everything seems fine and no new message appeared. Took the car out Saturday night and all was well, Sunday I did not use it, Monday morning it was completely dead. Wouldn't unlock, no lights on the dash, no beeps, nothing. I checked the battery at it was at 8 volts, and so I tried to jump the car. Even after like 15 minutes while being hooked up to my other car, no lights, nothing. I then hooked up a battery charger and after a few minutes it would tell me the battery was bad. I tried that a few times an keep getting the message, so I disconnected the battery from the car, and hooked up the charger to just the battery, and it has been charging for 10 hours fine. So it does not appear to be the battery.

Any thoughts what is going on? I should at least get power when the car is being jumped by another car. Did a computer in the car die? Or just some large fuse blew? Thanks for all your help. - Jeff

[chiefneil]

There's a lot of electronics between the charging posts under the hood and the battery. It's certainly possible something is messed up - I'd get it checked out by the dealer.

[tex2670]

I've seen a number of threads about this issue here and on other BMW forums over the last 2 months. Do you drive mostly just short trips?

[jknight]

Thanks for the replies. Most of my drives are to work which is 35 miles away. I worked on Friday, so Friday evening it "should" have had a good charge then. Saturday was probably a couple shorter 5ish mile drives. So I am guessing its not short drives as the problem. Also, the weather where I live is not terribly cold (Southern california). 40's at worst during the last week, so probably not a cold problem either.

[F30ed]

Originally Posted by jknight

I checked the battery at it was at 8 volts,

It is waaaay low. The CAS would shut down confort access at around 11.8v. After that current consumption is minimal, only fro key radio receiver. If it dropped to 8v, than it is either an uncounted consumer present, or battery is defective.
Do you have anything plugged in or connected directly to battery or anywhere to 30B terminal bus? radar detectors, dashacams..?

[jknight]

The only thing added was a Burger Stage 1 tuner. And a USB thumb drive into a USB port, but that can't be it. I would love it if its just a bad battery.

[jknight]

The battery is only a year old and looks really clean. But I know they can go bad much earlier than expected. I do use the stop/start tech, and I know that's harder on a battery.

[Billfitz]

Originally Posted by jknight

I should at least get power when the car is being jumped by another car.

Not necessarily. When a battery is sufficiently drained it just sucks up all the juice that the other car provides. It's not unusual in that case to have to disconnect the battery to jump start the car, then reconnect it afterwards, rather than leave the car doing the jumping running for an extended period until the battery charges enough to stop draining all the power away.
For it to go all the way to 8v either the battery is toast or something that's not influenced by the power management system is draining it.

[jknight]

Thanks, I will take the battery into a place and have them check it.

[401FlaGATOR]

When a 12V battery drops to 8V there is usually no coming back. A battery at 100% depth of discharge will drop to around 10.8V. Many battery connected devices such as solar charge controllers will have an LVD (low voltage disconnect) that disconnects the load from the battery at the 80% DOD (depth of discharge or 11.1V) to protect the battery from damage. The AGM batteries used in solar applications typically have thicker plates with less surface area than those used for automotive as more surface area is required to generate the higher cranking amps. As a consequence of this automotive batteries will often become damaged with a single discharge to 100% DOD, the plates can't handle it. It sounds like you had a constant load, a short circuit ( not a dead 0 ohm short but the higher resistance variety) that has discharged the battery slowly when the vehicle is turned off. You can try to replace the battery and monitor the new one closely with a DMM so that you can prevent the same thing from happening to the new one. A 100% charged 12V battery will range between 12.5 to 13V depending on temperature and battery chemistry.

[jknight]

Thanks 401FlaGATOR, that is very informative. What is a DMM?

[jknight]

Ah, just a digital multi meter.

[chiefneil]

Originally Posted by jknight

Thanks, I will take the battery into a place and have them check it.

If you're under warranty why not just have the car towed to the dealer and get a loaner while they check it out? You're going to want them to investigate why a 1 year old battery died regardless of what the battery place says. And I suspect you'd rather have the dealer replace the battery under warranty than buy a new one yourself, and to do that you'll need to bring the car in to the dealer. So all roads lead to Rome....

[HFW003]

Originally Posted by chiefneil

If you're under warranty why not just have the car towed to the dealer and get a loaner while they check it out? You're going to want them to investigate why a 1 year old battery died regardless of what the battery place says. And I suspect you'd rather have the dealer replace the battery under warranty than buy a new one yourself, and to do that you'll need to bring the car in to the dealer. So all roads lead to Rome....

He's in Simi Valley though

[chiefneil]

Originally Posted by HFW003

He's in Simi Valley though

Are you confused by my use of the phrase "All roads lead to Rome?"

That just means in this case that it sounds like OP is trying to avoid the dealer but no matter what he does, he'll end up there eventually. So might as well bite the bullet and just go now.

Every once in a while there's a post from someone under warranty going to great lengths to self-diagnose or repair their car on their own. I don't really understand what that's all about, personally. Unless you live hours from the closest dealer or somewhere really remote like Newcastle, I guess.

[jknight]

Thanks. I have no warranty, otherwise I would have taken it in), but yea, I may very well end up at a repair center.

So using a charger, I was able to get enough juice in the batter for the car to run. Which a charge in the battery, I noticed that when the car is off, there is often a 33 amp load and with that load, I noticed that the water pump is running. It does not run constantly, but I don't really notice a pattern. I have no idea why it would run at all when the car is not hot. But maybe it just runs for a while after the car is run or after power is restored? Also, when the water pump is not running, the load is like 5-8 amps, which still seems high. What kind of load should I see if the car is off?

I had read threads where the water pump went bad and ran 100% of the time which killed the battery, but mine does go off, so maybe thats the issue, or maybe not.

[Billfitz]

Originally Posted by jknight

Also, when the water pump is not running, the load is like 5-8 amps, which still seems high. What kind of load should I see if the car is off?

8 amps at 12v is 96 watts. That's a lot. One of your headlights is only 55 watts, and that will easily drain a battery overnight.

[ajob]

When you turn off a hot engine, you may have a 5-10 Amp current drain from the battery for 5-20 minutes, caused by radiator fan and water pumps, depending on engine type, engine temperature, etc.

When all this turns off, you may have a permanent 5-20 milliAmps (mA) drain for the alarm, remote door opening system, etc. In some cars this is further lowered after a few days.

Anything above that is abnormal or self-inflicted (satellite trackers, forgotten chargers, etc, but never above some 100 mA).

Based on your short (overnight) battery discharging time, I would bet that you may be suffering from a suddendly faulty thermostat that does not switch off the cooling pump after the engine has cooled - the repair center needs to check this.

[otay]

Originally Posted by jknight

Thanks. I have no warranty, otherwise I would have taken it in), but yea, I may very well end up at a repair center.

So using a charger, I was able to get enough juice in the batter for the car to run. Which a charge in the battery, I noticed that when the car is off, there is often a 33 amp load and with that load, I noticed that the water pump is running. It does not run constantly, but I don't really notice a pattern. I have no idea why it would run at all when the car is not hot. But maybe it just runs for a while after the car is run or after power is restored? Also, when the water pump is not running, the load is like 5-8 amps, which still seems high. What kind of load should I see if the car is off?

I had read threads where the water pump went bad and ran 100% of the time which killed the battery, but mine does go off, so maybe thats the issue, or maybe not.

Hmmm. 2015 328i with no warranty?

Could be many things...I once had a switch in the trunk go bad which left the trunk light on all the time. Took me forever to figure that one out. This is a complex machine...best to take it to the dealer.

[jknight]

Thanks everyone. Yea, I did research and it should be in the 50 milliamp range, but the car may have a higher draw than that for maybe the 15-20 after the car is turned off. I will try to track down the leak on saturday (with a current meter and pulling fuses one by one) and if I can't, take it in.

[jknight]

Ok, some followup.

When the trunk is open (or door or hood, etc), the car wakes up, which can including thing like the water pump running, so that is what I was reading. I saw this behavior when I closed the trunk and the water pump stopped immediately. So I tripped the trunk latch so it thought it was closed, and then I watched the amp draw for 3.5 hours. For about 5 minutes after the car was turned off, the draw was like 5-8 amps, then for another 5 minutes it was about 2 amps, then it sat at 30-70 milliamps for the rest of the time. That all seems Ok to me and confirmed what I had researched online.

So I was kinda stuck and took it to a friends shop that works on Lexus. The mechanic had me check the voltage when the car was running, and it was 15 volts! Which is too high. Luckily he was friends with the BMW shop next door, so he introduced me to the mechanic there. The BMW mechanic (after telling him my story), suggested it was probably the battery, and the high voltage was because the car knew it was dying and was trying to keep it alive.

I just finished putting in a new battery and registered the battery with the car (that was an adventure) and fired the car up. The voltage when the car is running is now about 14.2 which I believe is more reasonable. So I am hoping this is resolved. If my problems come back, I will reply back to this thread, so if someone else goes though this, they will know possible solutions.

[tex2670]

Originally Posted by otay

Hmmm. 2015 328i with no warranty?

I'd kind of like an update on this? Have you driven 50K miles in the past 2 years?