Mine is an 8 year old JumpStarter : looks like
http://www.diytools.com.au/default.a...}#imagegallery less the compressor (I have a heavy duty one for pumping up my tires after I leave the sand).
I have never needed to jump start myself with it , I have driven my Engal 39L carfridge for lots of hours with it, and run the occasional 12v bulge pump (as a live bait pump with it all night, more than enough power to run a GEM.
I also have a couple of my old 4x4 batteries that I keep charged up that I can use if I need some extra mWh but are not good enough to turn over the Pajero anymore.