Bests & Worsts Reviews from Amazon

I purchased the largest unit of these (GB-150, 4000 amps) This unit is awesome !!!! I am a Marine (Boat) Mechanic and run into Dead Batteries all the time and I Mean DEAD (less than 2 volts) This unit starts cold V8 engines like a new battery. I have tried all types of jump packs and this one is the lightest and most powerful of any I have tested. Now as far as the Amp rating (in this case 4000) I believe it is more marketing (Amps cumulative over time) VS actual delivered, for instance, I connected this unit fully charged to a 500 amp variable battery load tester to see what it could deliver, It maxed out at 420 Amps and held that for 20 seconds which is phenomenal !!! The units thermal protection kicked in after this. Realistically a modern V8 engine will average less than 200 amps while cranking and a 4 or 6 cylinder will be correspondingly less. Any engine will normally start within a few seconds. Now for some Battery FACTS ! Whenever a car battery (or any rechargeable battery) drops below a critical open circuit (no load) voltage (for 12 volt batteries this would be around 11 volts) internal damage begins and if one has a vehicle which drains a battery below this critical voltage (called a parasitic draw) you lose capacity every time a (what i call a destructive discharge) occurs. Under these conditions even a new battery may only last a few months and this applies to any type rechargeable battery Current rechargeable Lithium batteries would fail in one destructive discharge if protective circuits did not shut them off soon enough.