The cheap jump start is useless, it'll be gone in a few weeks.
I smashed a battery after only using it 10 times, in spite of charging it while driving around. The ramp is very steep and the Scorp weights 2000 kg fully loaded.
Now I run the car engine, using a stick between pedal and steering wheel for a bit of acceleration and that works out fine. No problems anymore. So the battery is charged all the time.