Just bought a jump starter as a backup in the event of a flat battery which happened twice a couple of years ago. It was a faulty battery even though the RAC guy said it tested as good. I chose this one (just search Amazon for "DBPOWER 1200A" if link no worky). One of the reasons I chose it was this one has an added feature of being able to charge the car battery via the accessory socket, which I would prefer to use if I'm not in a hurry as it would be safer on the cars electronics than an actual jump start. I guess the ignition would have to be turned on to enable charging via the accessory socket but that would be using power so I bought an adaptor to connect direct to the battery for charging. When it comes I'll check the amps it pushes in via the accessory socket and report back. I might even fit a permanent flying lead accessible from under the car, one like the Optimate uses. That would allow charging of the battery even in the event of a lock out, assuming I could get in the boot to get the power pack out. My blade key works fine, already tested it. Seems like an option others may be interested in as I've heard of a few problems with flat batteries that lock you out. Mainly on the two battery cars I think? Anyway, thoughts would be appreciated.