Charged once since I've owned. I've started cars, trucks, tractors, even my semi truck with this. If you're a trucker, farmer, fleet maintenance person, mechanic, or whatever you'll be glad you have this. Way quicker & easier than jumper cables. Peace of mind if your wife or children travel at night to know they won't be stranded with a dead battery. Recently the power went out for 2 days the cigarette lighter port kept 4 cell phones charged til power was restored. I honestly only charge this thing once a year & it will start anything. Update,,,4 years old now & still works great. Started 2 454 big block trucks back to back, then switched to 24 volts & started 1-10,000 watt diesel generator then 1-5,000 watt diesel generator. All 4 were so dead no lights at all would light at all. Didn’t charge the box b4 attempting either. Outside temp was bout 30 degrees. This thing is awesome.