Dropped keycard and battery came out, now it doesnt work halp?

Hi guys dropped keycard and battery fell out when i put it back in its coming up keycard not detected, how do i fix this? a;so where do i insert it into the car ive only just bought it and forgot to ask, 2006 197
 
might need soldering..search youtube..think i've seen a video on how to do it...
 
What do people think could be? Locks and unlocks intermittently no matter how long it has been driven. Main battery? Apart from that car is normal, headlights dim when first start and manoeuvre out of a tight spark for example.
 
If you take the key out that is in the key card it has a + symbol on it, that tells you what way to put the battery in. On topic my key card has packed it in all together so does anyone have a link for the soldering vid on YouTube?
 
Thanks [MENTION=41063]Pav[/MENTION]. Hopefully get it sorted mate as I like to have a spare card in the off chance something goes wrong!