I dont think the battery is charged from the car. As far as I know the batteries are not rechargeable and I cant see any way contact on the key.Do these not charge in the ignition ?
Might be an idea to drive around with that key in the igntion for a day or two and see if it charges if so ?
Unfortunately no recharging on these, unlike in some other cars!I thought some of them used induction charging.
If the original batteries are non rechargable then I assume not.
Panasonic VL2020 Rechargeable Battery BMW E46 Key Fob | eBay