KAF

Pre LCI refers to cars made prior to the mid life upgrade or 'Life Cycle Impulse' in BMW speak.

leo30d

so if you change your battery for any reason and dont reset or reprogram the car!! will the car still start and drive normal?

KAF

Many members have replaced thier batteries themselves without problems, others have had faults generated by the software.

Seems like you to have to hope for good luck.

Phil75070

Doesn't it also have to do with whether the replacement is exact in regard to the specs, CCA, etc? If the ratings/specs differ I can see a need to re-register the battery, but not sure that it would be necessary if the new battery is an exact duplicate. Just asking.

pete540

Phil, that is really the question that nobody knows the answer to. My suspicion is that if the battery replaced is an exact equivalent AND the old battery is not near death or completely dead, one could probably get away without registration . No actual knowledge of this fact but intellectually your battery loses juice everyday from non-use . I have left car for three weeks and restarted on return without any faults, so obviously one is going from a partially discharged state and the system can deal with this. I can't see how it would even distinquish one battery from another.

KAF

I wondered that, surely a battery is a battery.

Then I got to thinking about all the complicated electronics in these cars, if they have been running off abattery that is close to death, it might only be shoving out 8-10 volts at times. The power modules would shift power around to make sure essential items got all they needed. They would have to maintain a 'memory' of the power distribution for each start up.

If you then put a new battery on, dishing out the full voltage, the power modules might start putting too much power into some systems, on the assumption it is still dealing with a reduced supply.

registering resets it to original settings so replicating factory levels for each system.

Just a thought............................probably wrong, but a thought.

My car died three times in the winter, had to use starter cables to get it going from my wifes car, so it certainly will have had some fault codes stored somewhere as the i-drive went haywire when trying to start it.

cobradav

Most electronics do not run directly off battery voltage. There will be a voltage regulator that will step down to the typical electronic module to 5v range for standard electronic computers and microcircuits. THere may also be some that operate at lower or higher voltages but again these voltages are "regulated" so they can operate over a broad range of input voltage from the battery/charging system. Generally anything between 14.4 and 8-10 volts will get the correct output to teh desired circuit. However, going too high in voltage is another matter and can cause temporary overvoltage protection to kick in thereby rendering that module non functioning until voltage drops back to normal range.

EuroCarFan

First of, stupid question. What does AGM mean?

Second, I had replaced my stock battery with a lightweight "motorcycle" type battery (Deka ETX30L) a couple months ago to shave weight on my car. I saved 37lbs from the swap. The car ran fine for about a month even after I let it sit idle for several periods ranging from 2-3 days. Then out of the blue I got an increased discharge warning. It would come and go even though I was driving the car everyday so I got annoyed and swap back the stock battery.

I thought either the battery was too weak for application on the M5 or that it was just a bad unit but perhaps I needed this recoding done? Hmm.....

thedreamshop

AGM is different from the typical lead acid battery. AGM stands for absorbed glass mat, which means instead of lead plates in a pool of acid it is fiberglass matt with an acid gel absorbed into them. Usually this design allows more deep cycles than a lead acid battery and it has less resistance so it can charge faster.

thedreamshop

I think you are on to something here. The TIS document for the AGM battery states that you must not charge the battery above 14.8 volts. I have the ACM on my car which gives me a voltage indicator, usually it is around 14.1 volts when driving ( 13.6-13.8 with a/c fan on high and or headlights on ). But if my battery is low and needs recharging the car will raise the charge voltage as high as 15.3 but steady at 15.1. I believe you would need the software update to change the battery program to the AGM specifications. Otherwise, every time you exceeded 14.8 volts you would damage your $600+ AGM battery. ( real oem shows two AGM part numbers, both are over $600 ). A lead acid battery has more resistance in it so it can handle higher charge voltages up to around 15.5 volts.