Amazon product: NOCO Boost XL GB50 1500 Amp 12-Volt UltraSafe Portable Lithium Car Battery Jump Starter Pack for Up to 7-Liter Gasoline and 4-Liter Diesel Engines
I was sceptical about this technology but very happy in the end. We had some very cold temperatures and our tractor would not start. First try with the GB50 and it fired up. Will be very handy on the farm that is for sure!