Spare/2nd X5 key no longer starts car. How to recharge key?

[TurnAround]

2003 X5 came with 2 keys. My wife and I share the car, but I drive it 90% of the time. Her key has worked all these years, until this month. We went on a trip, loaned her key to a friend so they could drive the car to keep the battery topped off, and we received a text at the end of the trip, "Stranded. Car won't start".

We get back, try my key, and the X5 starts right up. Her key.. nothing.

So I'm thinking, "ahh... the key's battery is dead, which means the ignition won't recognize it". Funny thing is though, her key still unlocks/locks the car. Just won't turn over the engine.

Do you think it's as simple as a "dead key battery"? But, maybe the battery can still be recharged? How do I do that? Like.. maybe just put it in the ignition and turn to position 2 and leave it for a few hours??

Or... I've read gnarley stories about having to replace the key for $$$.

Thanks

[jsoto]

TurnAround -

Sent my key in here....https://www.bmwgm5.com/
$50 per key.

Working after repair - about 2 months sofar

[jsoto]

Option 2 FWIW

For a $160, get a brand new key.
It will be 100% weather sealed so it depends what ROI you want...

[TurnAround]

Thanks. Those are good options for replacement.

But.. so.. the existing key can't simply be recharged?

Also, is the diagnosis even confirmed?; Is it that the key battery is dead? Or, are there other trouble scenarios? I guess I don't mind replacing the key, but I'd like to know what went wrong. Did I just need to use that key once a month for an hour, or something like that?

Thanks

[gatojurko]

Rechargeable battery can last about 10-12years... purchase reachargeable battery from China for 10-20$ and done!
5h on position 2 it will be an end for your car battery! It will be just empty!
Key unlocks doors manually or with buttons? Does work any other options with options? Panic alarm,windows,interior lights?

[jsoto]

I had same symptoms....
It was neither. A wild guess is the coil in the key is bad.

[TurnAround]

I just tested it again. The key will reliably unlock or lock the car remotely, over and over. Windows and interior light also work as normal. It just won't start the car is all.

So... maybe the chip in the key has partially failed.

Replace the key, eh? Sounds like that's the situation.

[gatojurko]

Something with chip or signal reading! U could take it out and place it more closer or try to place second key near ignition hole and start with 'broken' key

[wpoll]

You will need to replace the key or have it repaired.

The battery only powers the remote central locking - and clearly the battery is fine, as that is working.

The ignition is enabled by the prescence of a small externally powered transmitter in the key fob - it transmits a security code to the car when the key is in the ignition. This transmitter is powered by a small electric field generated by a coil around the ignition switch. A similar field charges the battery for the central locking remote function.

It's possible that one too many drops of the key has damaged this small transmitter in the fob - which is basically just a tiny aerial coil and a chip. They can be repaired if its a simple mechanical fault (broken wire or solder joint) but beyond this, it's time for a new key.

I have built a new working key from components purchased from eBay but for a VW, not a BMW, and I still had to get a VW dealer to re-program the car to accept the new key - something BMW delers cannot do.

[upallnight]

Originally Posted by TurnAround

Thanks. Those are good options for replacement.

But.. so.. the existing key can't simply be recharged?

Also, is the diagnosis even confirmed?; Is it that the key battery is dead? Or, are there other trouble scenarios? I guess I don't mind replacing the key, but I'd like to know what went wrong. Did I just need to use that key once a month for an hour, or something like that?

Thanks

Battery in the key is only for remote locking and unlocking the doors. There's a transponder chip in the key that work with the EWS to start the engine. No battery is required to activate the transponder in the key.

Since the key still unlock and lock the doors most likely the transponder circuit is damaged. Did you tried the wife key before giving them the key? Did your wife ever drop the key?