The idea is TD, not to let the battery 'die' in the first place. My last battery died after I had been on holiday for 2 weeks. Neither myself, or the RAC bloke could get into the car forcing the key.
Had to put a current through the starter motor to get into the car.
I think, and so does Mark, that the charger would provide enough current to operate the doors by remote.
Although I have a double garage, my car will not fit in it, so it tends to get left out on the drive, the project seemed to be an easy way of charging, and an emergency power supply source, if needed.
If the battery ever dies again, and the charger will not provide enough current to open the doors, I can easily connect another battery to the socket, without (a) trying to force the lock, or (b) crawling under the car to try and get some current through the starter motor.
What I shall do, next time I go on holiday without the car, is to connect the charger to a timer, and give the battery a trickle from time to time.