Every time you drive the car, the alternator should be keeping the battery fully charged. If you had the dash-cam switched on and recording for 18 months without driving the car, then, yes, it would definitely flatten the battery. However, it shouldn’t really pose any threat to the alternator. It doesn’t really matter what’s draining the battery, be it a dash-cam or the headlights or the stereo system; if the car gets regular use, the alternator should be able to stay on top of things and keep the battery charged and in good health. This sounds more like your dealership blaming the dash-cam as the cause of a failed alternator, when the problem was possibly a dodgy alternator all along.  Don’t accept nonsense like this. Take the car to an auto electrician and have the thing diagnosed properly. Then by-pass the dealership and contact LDV’s Australia customer service number. Your vehicle should still be under factory warranty, so make it LDV’s problem. And if the car’s alternator can’t support a dash-cam, then it’s probably not fit for purpose, at which point the ACCC and Australian Consumer Law might be interested.