You can jump start a vehicle with at least 20% battery level of the jump starter.
Keep the battery level above 80% for a better starting performance
However, we highly recommend you recharge the jump starter every 3 months to keep its battery level above 80% or fully charged.
Even though our product can start dead battery vehicles when the battery level of the jump starter is 20%, we still suggest you recharge the jump starter to above 80% for the best performance. When starting a completely dead battery, the car engine requires more power.