i don't have a 'jump pack' yet
but between, (2) battery chargers, with start function, 70amp converters, big house battery bank etc..
the only time i ever had a problem was with a dead battery on the scoot
(doesn't count previous RVs)
i have used the vector charger with start on numerous cars and vans, just run out the 50ft extension cord and plug in the charger, to generator or inverter
i started a friends car this way just a few days ago
most of the time they are parked in such a manner that i can NOT use jumper cables from my battery bank
i have thought about a Li jump pack, just to save some time and effort
"helpful guy that i am"