Compatible Models:
BMW E39 and E46 keys (Diamond Keys).
BMW E90 /91 /92 /93 as well as many BMW key fobs from the early 2000's
The keys can be recharged (using induction) when inserted in the ignition. However, like any rechargeable battery, they are only good for about 1000 charges. The keys are sealed and typically cost between £150 - £250 to purchase from BMW. But with this battery, you can simply replace the battery yourself. To do this, you will need to cut open the key with a sharp object, replace the battery, and then reseal the key. There are many guides available on the internet to help you with this process.