Pull the battery cable connector towards the battery to disconnect it from its socket.

If the connector is stubborn, push a little at one side, then the other, to "walk" it out of its socket.

If you have trouble walking the connector out of the socket, use the point of a spudger to gently push on the connector indent to slide the connector out.

Open the display and press the power button for five seconds to drain any remaining charge from the system.