If you do decide to cut the lock off one of these pesky devices, leave them a new lock (with it's keys) exchange is no robbery.These 18v cordless will work fine from a 12v car battery. Just pick up a cheap one - perhaps with a duff battery, cable it up with a pair of crock clips one end and leave it in the car boot..... just in case you need to cut a padlock of a certain device - which shall remain nameless.
Power to the people.... and your angle grinder!
Wotan