When to change batteries

[Scissorshand]

Just changed, cost me $400, they came over my crib

 

[Nmr Nik Soh]

Finally i decided to not register my new battery on my car, bimmer who own 5 series/bmw owner workshop at subang bestari n my friend mech at subang bestari also(he was ex karamjit singh mech. n expert on subaru) give me their opinion..

 

[Scissorshand]

Apparently the installer had the engine running while changing the battery hence I didn't need to register the new battery

 

[kolamp]

We need to register the new batteries because from what ive read, BMW uses an "intelligent" alternator variable algorithm that monitors the attery condition (charge, rate of discharge, etc) and simply shuts on and off depending on this condition. That reduces engine load thus increasing efficiency -power and economy.

From my understanding, old battery should have higher charging or discharging rate due to wear & tear compare to new batteries which require lower rate. Thats why we need to 'tell' the ECU that ure replacing new batteries so that the ECU won't overcharge ur new batteries thinking its still running on old battery. It just to prolong the battery life but if u don't register ur battery, u can still can start ur car no worries :rock:

 

[Nailofar]

you need to register new battery if you change to different capacity battery. for my case, i changed from din88 to din100. slightly bigger capacity. ECU need to know the new battery and act accodingly such as alternator charging, etc to prolong battery life.