dead battery.....

[SmbFD3S]

Ok guys so found out why the alarm keeps going off, cos it\'s sensing the battery voltage drop....most annoying but at least it\'s a simple fix hopefully.
 
Just wanted to ask, is it critical which battery goes in?
 
Standard RX, no fancy gadgets or anything although do have an Apexi PFC and commander. Basically i have a spare battery, which is rated at 55ah, would this be ok ??  If i can get away with not buying a new one that would be good.
 
Btw, only just fitted the PFC and wondered how you guys have secured yours as the original ECU was screwed in ??
 
Cheers, Scott