08-535i sport

So I have been having the excessive battery drain or whatever it is warning....I do not drive long trips and the car sits for days sometimes. Yesterday the car was "dark" and would not start or even turn...it was dead, nothing! Based on other things I have read, I bought a battery tender yesterday and got the battery good and charged and no problems/warning since. Until a bit ago, I was parked talking to my neighbor, car was off, and I had the door open. After only a few mins, the orange battery display lit up on the dash. Does indicate alternator, or could it still be battery? I know I should/need to have the alternator tested and will check the voltage on the battery, but want to have some input from here. Thanks!

roskinc

you could always have it checked. most places like autozone check it free of charge..

my quess would be the battery, short trips doesnt allow enough time for battery to charge. if its been low for a while, or dead, it kills the battery cells. you could take a brand new battery, and if it gets discharged, even it being new will kill the cells...only a heavy duty can be drained and recharged

08-535i sport

Do I have to take the alternator out to have it tested?

SilberGrauE60

I think he was referring to the battery for the checking--take it to the store and they will put a tester on it. I would guess the alternator needs to be checked in the car while running.

There is a hidden OBC menu that will show the current voltage. With the car off it will be the battery voltage. With the car running it will be the charging voltage.

Do a search for "hidden OBC menu" ... or download/read the attached. Option 09 is the battery display, after you unlock via option 19.

BimmerFan52

+1 Check battery and alternator

Given your description it is very likely the battery.

If you go to an auto store they will hook a hand-held computer to the jump terminal and ground terminal under your hood. Nothing needs to be removed from the car.

It will measure the battery voltage before you start. Then you start your engine and it will measure the starter performance and alternator output and tell if any of the three devices appear to be defective.

In my case I went to confirm what I already knew - the alternator (voltage regulator) was putting out 17V on start up.

Search this forum for model number recommendations for equivalent replacement batteries. If you buy the same type of battery it is up to you whether you have the battery registered in the software. Registration tells the car computer that the battery is new, and that information coupled with the current battery voltage and temperature (measured by the IBS or intelligent battery sensor) allows the computer to communicate with the alternator and tell it what output voltage should be applied to the battery to keep it in prime condition. As the battery ages (computer knows how old it is from the installation date) the alternator voltage is varied (usually increased).

There is much debate as to whether registration is necessary. Some swear by it and others say it is a waste of time and money. If you get a good deal on an auto store battery (same type, size and venting capability) you should spend $100-$150. If you decide to have it registered an independent BMW shop should charge around $50.

A battery from most dealers runs anywhere from $350-$750 depending upon how badly they want to gouge you.

You may want to buy one of these handy power socket voltmeters for the future. Just plug it into the cigarette lighter and measure voltage before starting the engine (battery) and the voltage after starting (alternator).
PRIME PRODUCTS - Prime Products Digital 12 Volt Meter For Cigarette Lighter - RV Plus

08-535i sport

Thanks guys, went to Autozone, everything was testing good which means it is the battery since it was on a tender all night. I just need to confirm if the battery has ever been changed (I am the second owner). If it is the original, obviously time for new...if it has been replaced, then I am one of those terrible BMW owners/drivers that does not drive my car enough or for long enough trips to get/keep the battery charged and will have to utilize the tender.

I almost bought one of those power socket voltmeters yesterday when I bought the battery tender....looks like I should have and will be picking one up