battery could be knackered, seen batteries with 12v on meter but current reading less than 1amp, cells had gone low resistance, check battery resistance with meter.
Anybody got a decent service checklist i can have a look at for cctv / access. Just in the middle of rewriting ours for, so far intruder has been cut down to 12 points which is now going to be cut down to 11 as i think the last two are the same question.