The jumper cables are for running the compressor on 12V while filling and testing. The traction motor draws roughly 600W idling at 12V. The air conditioning system increases power draw by roughly 700W.
The battery may look like this box. So I want to work the kinks out of the air conditioning before being encumbered with it.
Evacuated and filled with R134a. Ice-cold!
Well, it was ice-cold then the compressor made noises and seized up. I learned that a refrigerant compressor has to be mounted right-side-up. There is an oil plug on the body which has to be within 90 degrees of up. It probably ran for 30 minutes upside down - don't do that!
New compressor installed. Air conditioning complete.
Tools acquired: AC gauges and cheapy vacuum pump from Harbor Freight