2002 E66 Battery Replacement - Sorry, singing that same tune!

[Calli74]

OK, I was wondering if anyone had any recent information with respect to replacing their car batteries. I have a 2002 745Li - never had an issue with it with the exception of some secondary air valves/pumps in the the emissions systems.

Anyhow - my battery was weak yesterday and today I had to jump my car to get her going. I'm not sure if this is the original battery. I'm going to take a look later today. Regardless, I've started pricing the batteries. I've gotten quotes from $129.99 - $260.00. No labor included. BMW says it's a 1hr service. Local mechanic says it's all done within 30min - tops.

SO here is my question. Will I absolutely need to "register" my battery? :eyecrazy There are so many contradicting stories on different websites. I want to be 100% sure. Also - what is involved with the "registering" if I do go that route? Can a certified BMW mechanic do it. (Non-Dealer) What tools do they use to register? Any an all information is appreciated.

Thanks in advance!

[KeifR]

In BMW's TIS it says that "In principle, any conventional lead-calcium battery can be exchanged for an AGM battery. The use of an AGM battery has no consequence for the vehicle's electrical circuit." It goes on to specify that because of the high power demands of these and a few other cars that only AGM batteries be used.

It also says, "In principle, the battery must be registered with the BMW diagnosis system after every battery change...If the service function "Register battery change" is not run after changing the battery, the data stored in the power management will not be reset. The battery quality will then correspond to an older battery. The value for the battery quality is insufficient for the battery installed. The battery charge state may then be misinterpreted and unnecessary Check-Control messages may appear or fault memory entries may be stored (e.g. the Check-Control message "Recharge battery" even though the battery fitted is new and fully charged."

From BMW's WDS:

"Battery replacement

This function informs the power module of a battery change. The following operations are performed:

The battery capacity is reset depending on the seasonal temperature.
The current kilometer reading is stored.
The stored battery statistical values (current, voltage, battery charge state) are deleted.
The stored temperature statistical values are deleted.

The seasonal temperature is an average battery temperature value spread of the last few days

Values for the charge level following the diagnosis command "Register battery replacement" dependent on the seasonal temperature.

Seasonal temperature / Capacity value

< 25 °C / 98 %
-10 °C / 68 %
0 °C / 66 %
10 °C / 63 %
20 °C / 61 %
>30 °C / 58 %

This value is retained until the vehicle has been deactivated for at least 6 hours. Thereafter, an open-circuit voltage measurement determines the capacity. The value determined in this way is entered in the power module."


Take-aways: get an AGM (glass mat) battery and register your battery.

Some non-dealers may be able to do it, but just doing registration should be very quick at a dealer.

[02325]

i have also seen the alternator go wide open and blow your newly $200 dollar battery up. I had a tech install a new battery, go for a test drive and did not registor the battery, 5 miles later he called for a tow truck b/c the battery blew up. Check faults and it said alternator charged at 19V. before battery change no overcharge faults were stored. So I guess it is up to YOU.

And yes go with AGM only. it is best for your electrical car.