Electric ram from Ultraflex, but it's marketed under loads of other names too.
It's operation is nice n quite, but a bit slow, and it doesn't hold the hatch shut, so you still need a safety device, in my case, a little rubber hook thingy, but it does mean you can get it open in the case of a battery/wiring/ram failure.
A couple of years ago I saw an HTM cat in which the engine room fire exstinguisher had broken free, it ran a-mock in the engine compartment for an hour or so, smashing amongst other things, the connections onto the hatch lifter motor!, and guess what, no facility to disconnect the ram!
, dunno what they did in the end, but I couldn't watch as they tried to prize it open