Ford 2000 E-150 Owner's Manual page 172

Maintenance and care
1. Disconnect the secondary positive
cable from the primary battery
terminal.
2. Wrap the secondary positive cable
with a non-conductive material to
insulate.
3. Disconnect the primary battery
ground cable.
4. Disconnect the primary battery
positive cable.
Connect:
Secondary positive cable remains energized after disconnection.
make sure the tool does not contact any ground surface.
172