My NorthStar sprayer from N.H. Northern came with a an 18" two strand wire with U-terminals on the ends. These connect to the battery. There is a little plug on the other end. I just let this go over the screen between the operator's seat and the battery. This wire always stays connected, with about 4" hanging loose. The sprayer has a long wire which plugs into the short one.
I bought the type sprayer designed to bungee onto the back of an ATV. To use it, I attach my carry all to the 3ph, put a plank on the carry all, set the sprayer on the plank, and bungee the tank in place. Works well.