Electronis Key Battery
 

Can anyone tell me what battery fits the key for a 1999 E320 and where do you insert a screwdriver to pry it open?? Thanks!!
Never mind---I found out the CR2025 is the correct battery for this fob and ordered 5 of them for a total of $6.93 w/free shipping. WalMart wanted nearly $5 for one so it will now allow me to replace the batteries in both fobs. Got them from Bob's Batteries in case anyone else needs any.

If you happen to have your owners manual I think it is explained in there. The only trouble I had was actually buying the battery. I went to a camera store to find it.

That's a good price on the batteries. If someone needs a replacement quickly, Radio Shack carries a pack of 3 for $12. Most Walgreens carry them too.