I have to admit I bought this unit a little sceptical that it was actually going to be capable of turning my 2008 Mercedes E320 Diesel Saloon. My old jump starter/tyre pump unit didn't even come close and when I called out roadside assistance he lugged over a huge battery pack to get the job done and told me this 3 ltr diesel engine needed something really powerful to crank it cold. So, some months later, when the car had sat unused for a month or so while I was in England, refused to start with only a 'click' in response to a turn of the ignition key. And so, enter this unit: I charged it over night, clamped it to the very-near flat battery and the engine started on the first turn! Wow! The unit is also holding its own charge very well in storage too. Could not be more pleased.