It depends on your vehicle types, and HULKMAN Alpha jump starter is designed for 12V system vehicle.
And normally there's two kinds of situation:
1) If you have two batteries in parallel for a 12V system, then it is a 12V system.
You can use it to jump start your 12V car.
2) If you have two 12V batteries in series, then it is a 24V system.
You can not use it to jump start your 24V car.
The engine rating that HULKMAN Alpha jump starter works for:
Note: We recommend you to charge your jump starter’ battery level above 80%, so that It's more possible to kick out your dead batteries