Leisure battery

Bigmarkh9019

My compass 634 main battery is going flat and i suspect the alarm.  i have heard about the alarm module back up battery could be duff.  Anyone know the best place to get one and where it may be located.  Im sure ill find it but simply asking to save time. 
Is an EHU enough to recharge the battery or do i need to take it out and put it on a charger