2007 4.8i DOA...
 

Put gas in my car yesterday morning, 10 miles round trip. Came back home, parked the car and went about my day. Went to go out at 6PM and it wouldn't fire up. The idrive screen turned on and there was a Christmas tree of lights on the dash but the starter wasn't clicking.

Threw the battery charger on it last night (CTEK) and it says it's still charging this morning. I have a high capacity AGM in there that's only 4 months old....any idea's on what could've happened? Did the car get stuck in a loop and never go into sleep mode during the day and burn the entire battery down?

Edit 1:
I read a few other posts, and it seems like it could be bad gas, or that the fuel pump is shot. Hopefully I can get it up and running and it doesn't need to be flat bedded to the dealer.

Edit 2:
Battery Charger said the battery was fully charged after 18+ hours on the charger, Checked the voltage, and then tried to start it, fired right up. Checked to make sure it was charging and it was. What a weird gremlin I've got in my car.

Edit 3:
And dead again, up to the dealer it goes. This is super redic. Hopefully they can figure out what the issue is.

Sounds like a batt issue. I know AGMs are tough, but your symptoms seem to point that way. Im curious to see what the dealer says.

Doing this from recall, but when you replace an old(er) battery, you need to tell the car's computer system that it there is now a "new" battery in the car (go to dealer). The reason behind this is that the computer is programmed to continuously update the output from the alternator over time as the battery ages. After about 4 years or so the alternator may now be putting out 20% to 30% more charge just to keep the weak battery at peak capacity.

If you don't reset the computer, the "new' battery will now be over charged because the alternator is still putting out the charge for an old(er) battery.

Overcharging can be disastrous to the sensitive electronics in the car over time. But I suspect that what might be happening in your case is that the system quit charging the battery and that you basically ran the car from a fully charged battery, until such time that the battery charge was used up again ...

Get the car reprogrammed at the dealer. Count on doing this every time you replace the battery (unfortunately).

Dealer was the one that performed the initial install of the new AGM battery and did the reprogramming of it.

They actually determined that there is a bad cell in the battery and it will never be reach a full charge....being replaced for free under warranty tomorrow. No big deal...besides the inconvenience factor.

There is a simple 'registration' process ("programming") that can be done with any BMW computer... it is NOT as critical as your recollection suggests. It will only result in POTENTIALLY a shortened new battery life- like 25%. (IMO)...It should NOT cause this excessive drain or inability to charge/hold a charge.

Simple registration
 

Ard, is this simple registration process something the DIY owner can do? If so, would you please elaborate?

TIA,
Dick

Please explain. I can understand how overcharging can shorten a battery's life, but can see no way this could damage any other electronics in the vehicle, since the voltage regulation always keeps the system voltage within the design range of the electronic components.

What is your source of this information?

Car has been fine since they replaced the battery, guess we can just chalk it up to bad luck

It's current (amps) not voltage that causes damage. Much of the cars sensitive electronics draws micro-amps ... it doesn't take much.

I learned this in high school ... and from a close friend of mine who is a BMW master mechanic who has seen his share of BMW's get towed in because of fried electronics due to a lack of reprogramming the cars computer after replacing the battery ...

No, it not going to kill your sensitive electronics (they can do that well enough without any help) its just something BMW programmers made to help lengthen the life of your battery, agm batteries can be fickle. Plus that cars are super rough on batteries, with large stagnant draws, and the battery needs all the help it can get

Sent from my SGH-i917 using Board Express