Old battery experiment
 

What would happen if you had a 4 year old battery and went through the INPA registration process and registered it as new?

In theory, it would attempt to charge it at an incorrect rate. Why not simply buy another battery? Depending on what you have, not a bad idea to replace them every 4 to 5 years as preventative maintenence

If a 4 year old battery was inadvertently registered as new with INPA, you mentioned in theory, it would attempt to charge the battery at an incorrect rate.

Many people have bought new car batteries that have been sitting around for months and did not hold a full charge when installed. When those batteries were registered with INPA or other scanners:

a) how did the BMW charging system know the correct rate to charge the depleted battery?

b) when a battery is 4 years old and has always been on a Delran trickle charger with a full charge, how does the BMW charging system know the proper rate to charge the old battery?

The IBS also measures the "state of the battery charge" and temperature in addition to the date of registration. Depending on the state of the battery as measured by the IBS, the charge system charges as necessary. If your battery is 4 years old, but been on trickle charge all that time, then I would consider it "new", and register it as such.

Go ahead and try the experiment and see! After all, you presumably "know" what the "true" state of the battery is and won't be surprised if problems come up later.