I can trace a fault through any pack and bring it back to life, and there's not a battery system that intimidates me anymore. But every time I connect those leads I'm one wrong move from hundreds of volts that don't forgive mistakes. I'm the one they call for the hard jobs, and I carry the danger of them quietly.
More people experience this than they realize.
You can fix any battery, and you carry the high-voltage danger every time.
If this sounds familiar, the Library can help you find the bigger picture.