Hey all

Driving a '06 523i with 82k miles on the clock.

Had to replace the battery recently after a number of failures to start. The new battery is going great but I never registered it with the ECU. As a result, the rear-window demister refuses to work and the aircon fan only operates at the lowest speed (intermittently).

After reading up on the IBS in these cars, I decided to unplug it the other day. All problems have now gone away. My question is this: can I leave the IBS unplugged indefinitely? What issues, if any, would this cause?

Cheers.

 

When the IBS detects the battery is in a low State of charge (SoC), it turns off the rear screen heater and fans down to 75% of max and a few other things down/off. Now the problem is, when you swap batteries over, the car doesn't know how full or empty the new battery is, which is why you "register" it, it resets the SoC value.

The car uses information form the SoC to determine how much to charge the battery by (on start up, my voltage is 14.5- 14.7, after a motorway run, it's around 14.2- 14.4.

Not having an IBS means the battery could wear out prematurely from overcharging, it won't get charged intelligently, and you won't get the power saving features when the battery is low on charge but it can't switch off non-essential electrical items.