Hi Tony
Welcome to the forum
The idm4 alarm has a back up battery that needs to be recharged every 8 months max, if you look at the alarm battery housing you will see a jack plug for a charger as far as I am aware the 12v input is only for day to day running of the alarm the back up battery is for drained /stolen leisure battery but for some unknown reason the 12v system doesn't charge the alarm battery. Must be a caravan thing!?
The backup battery may /probably will need renewing if it hasn't been charged, please see attached image for specification of charger.
Gra
