I'm replacing the batteries (2 x 12V, in series) in a Best power supply from
the early 1990s.

Obviously, I have a negative lead, a jumper to put the two batteries in
series, and a positive lead.

Attached (with tape) to the red positive lead is a white wire with a smaller
female spade connector on the end of it. The person who previously replaced
the batteries did not connect the white wire to anything. What should it go
to?