The reason why you can't charge and discharge at the same time
1) It is not safe, which may shorten your jump starter lifespan.
Charging and discharging at the same time would generate too much current. This could cause the jump starter to overheat and may even explode. Therefore, we don't recommend you charge other devices when you are charging your jump starter.
2) It may shorten your battery circuit.
It may shorten your battery circuit due to too much current generated. For the protection of the battery circuit, please do not try to charge and discharge at the same time.
These 3 tips show you how to maximize your battery performance: