[turbolover]

I have a 2008 BMW 335xi 2dr, fully loaded. I noticed if the car sits for 2-3 days the battery gets low some how? The car will still start with no problems but I keep having to reset the date and time, and the "!" indicator shows up and on the more detailed side the service options in the navi screen says a generic mesage something like "batter discharge, something is draining the battery when it's off?"

I called a few BMW dealerships, one dude said change the battery, another dude said get a bettery tender? and this is so common, because the car has so may electricals in it the battery is usually never off 100%?

Is this true? Do I need a new bettery? Or did bmw do this to where I am forced to drive my car all the time! LOL

Anyone have any input?

[ajsalida]

Same problem here, took it to the dealer and they said battery was good still just needed a charge + "software update". Fine for 6-8 months. Then started doing it again this winter. Always seems to happen when it gets cold. Anyway I charged the battery on 2 amp trickle for 2 days (until light went green on the charger), appears to be fine now.

I think the whole charging system/software is far too complicated for its own good on these cars. There is an internal software model of the battery charge state and alternator output etc., if anything gets skewed it reads "battery discharge while not running" and zeros out the trip odo and other settings. Like when it gets cold.

Really stupid IMHO.

[NiVeDh]

If it's an '08, it's about time for a new battery.

[fazman]

I had the same problem on my CPO 2008 335xi sedan, when I first bought it. Problem was two fold.

1) Bad IBS cable, it eventually tossed a code and the dealer replaced it under warrenty.
2) It also had to do with me driving so little in the beginning. After the IBS cable was changed and the dealer charger up the battery for me... everything has been smooth so far (knock on wood).

I also agree with the others, my car has build date of June 2007 (Model year 2008). That means my OEM battery is 5+ years old now, it is running on borrowed time. I've started researching where to change the battery and costs + battery registration. One dealer quoted me $300, I think that is a good price for a dealership to do it (but realistically the battery should only cost about $120 + $30 labor so they are making a mint even at that price). I'm going to see if my SA will just do the registration for me if I buy and install the battery myself... but I'll have it done when I pay them to do the next oil change.

FYI - All batteries tend to die in the winter months, because it's the worst time to work on a car and also the days get darker faster <sigh>

WARNING - never-ever have anyone jump start from the actual battery in the trunk, you have a positive and negative post that is run into the engine bay from the trunk. USE THE BATTERY TERMINALS IN THE ENGINE BAY to jump start with your BMW. If you do it from the actual battery in the trunk... you will blow out your Junction box and that is a cool $1k to have replaced and recoded to your car.

- Faz

[ajsalida]

Update to my original post above, I found that trickle charging the battery @ 2 amps for a day or two gets it to a charge level where this does not happen anymore. I think the internal software model is such that it is not accurate WRT charge state of an older battery in fall/winter and it gets into this loop of not charging enough while running.

Before getting a new battery and all the headaches that entails (reprogramming ECU) I'd try giving it an overnight trickle charge or two, thru the under hood posts as above is fine.

[vapore0n]

My battery comes up with this error when I detail the car. Too much opening the doors, or leaving them open (even with the lights inside off).

Wish this car had a real off switch. That way I could work on the car and not drain the battery.

[ajsalida]

Originally Posted by vapore0n

My battery comes up with this error when I detail the car. Too much opening the doors, or leaving them open (even with the lights inside off).

Wish this car had a real off switch. That way I could work on the car and not drain the battery.

Put the key fob far away, if it is in your pocket while you wash or fiddle with the car, it keeps the ECU awake and waiting to do something. I do this now always when I work on the car. Lets the ECU go to sleep and stay asleep so the battery does not drain.

[linlaoboo]

which dealer quoted you $300? My dealer quoted me $366. I tried slow charge and rapid charge last night and the start button, glove compartment and trunk lights keep flickering making this weird noise throughout the car. My charger doesn't have a trickle charge function but it has the maintain function. Is that the same?

My battery might be beyond saving since the round window on the battery stays black and it measures 4.6V . . .

Originally Posted by fazman

I had the same problem on my CPO 2008 335xi sedan, when I first bought it. Problem was two fold.

1) Bad IBS cable, it eventually tossed a code and the dealer replaced it under warrenty.
2) It also had to do with me driving so little in the beginning. After the IBS cable was changed and the dealer charger up the battery for me... everything has been smooth so far (knock on wood).

I also agree with the others, my car has build date of June 2007 (Model year 2008). That means my OEM battery is 5+ years old now, it is running on borrowed time. I've started researching where to change the battery and costs + battery registration. One dealer quoted me $300, I think that is a good price for a dealership to do it (but realistically the battery should only cost about $120 + $30 labor so they are making a mint even at that price). I'm going to see if my SA will just do the registration for me if I buy and install the battery myself... but I'll have it done when I pay them to do the next oil change.

FYI - All batteries tend to die in the winter months, because it's the worst time to work on a car and also the days get darker faster <sigh>

WARNING - never-ever have anyone jump start from the actual battery in the trunk, you have a positive and negative post that is run into the engine bay from the trunk. USE THE BATTERY TERMINALS IN THE ENGINE BAY to jump start with your BMW. If you do it from the actual battery in the trunk... you will blow out your Junction box and that is a cool $1k to have replaced and recoded to your car.

- Faz

[VMRWheels]

Originally Posted by fazman

WARNING - never-ever have anyone jump start from the actual battery in the trunk, you have a positive and negative post that is run into the engine bay from the trunk. USE THE BATTERY TERMINALS IN THE ENGINE BAY to jump start with your BMW. If you do it from the actual battery in the trunk... you will blow out your Junction box and that is a cool $1k to have replaced and recoded to your car.

- Faz

Good info. Ty.

[fazman]

Originally Posted by linlaoboo

which dealer quoted you $300? My dealer quoted me $366. I tried slow charge and rapid charge last night and the start button, glove compartment and trunk lights keep flickering making this weird noise throughout the car. My charger doesn't have a trickle charge function but it has the maintain function. Is that the same?

My battery might be beyond saving since the round window on the battery stays black and it measures 4.6V . . .

Bloomfield BMW, NJ on the GSP north @ exit 148. My SA is Jin Yoon, tell him that trouble maker faizal sent you. and bring him one of those starbucks ice coffee's in the glass bottles

- Faz

[fazman]

Originally Posted by VMRWheels

Good info. Ty.

Your welcome... and I found out because this happened to another guy and my mechanic was trying to fix it for them (learn from other peoples examples).