Comment by spuz
3 years ago
What is the story here exactly? Is there an official way to replace the battery that doesn't require a dongle? What does the dongle do exactly? Why does a new battery get drained if you don't follow this process carefully?
The charger learns how worn the old battery is, and overvolts old ones to get a bit more useful life out of them. When you disconnect and reconnect the battery it doesn’t reset the training algorithm, so it overvolts the new battery, reducing its lifespan to roughly 30 days.
There’s no official way to reset the charge algorithm without a dealer-only dongle, so you take it to the dealership to replace the battery (~$400 labor, $100 parts).
They could solve the problem by adding a “register 12V battery” option to the service menu, or by having it prompt the next time you start the car after 12V power is interrupted.
That makes sense. Manufacturers keep proving to us they don't value making maintainable products so it seems obvious they need to be forced to do that one way or another.