Key not working, then working after placed in ignition?

[DavidPartay]

Recently the transponder for one of my keys stopped working, so I cracked it open to have a look at it and possibly replace the battery.

Then, my other key stopped working today, so out of desperation I tried it in the ignition and turned it to the on position, and then it started working normally again. I put the other key back together, tested it, not working, put it in the ignition and turned it on, then tried again and it was working fine.

Here's my question? What on earth is the deal with that?! Does it sound like the battery is dying in the transponder, or is it some weird coding glitch which gets fixed up when you put it in the ignition? Or, static, or something like that? I don't understand how these particular electronics work so it's really bizarre to me.

[feistl]

Battery in the key is flat. What its put in the ignition it gets power from the car, enabling the immobilizer to be disabled, and the car started. The metal "prong" bit and the actual metal key create the circuit to power the key

[DavidPartay]

But the battery then continues to work just fine even when the key is removed from the ignition, does it store a decent amount of power into the battery? I wouldn't have thought they'd be rechargeable... The fob works just fine now.