Earlier mention about putting in the chemical, and then putting in the water, results in a high-amount of foaming. I can attest to that, same results for me, when approaching the fill-up in this manner.
Recommended approach I would suggest, is that earlier mention of filling up about 3/4 full with water, then put the solution in, and top it back off with the water, which should create enough 'agitation', to get the solution mixed around in the tank.
Earlier mention about using the sprayer, just connecting to the ATV battery with the supplied alligator clip power on/off unit, I do it this way, and have had no problems. Now, though, I'm not using the sprayer weekly, or even monthly, maybe just a couple times a year, for a duration of only 15-20 minutes each time. Not enough 'abuse' to the mechanics of my Polaris Sportsman 570, that gives me any concern.
I've got the 31-Gallon Northstar tow sprayer, and for the most part it's been a good unit, other than one thing that caused me a lot of time/energy. Keep yourself a spare alligator clip on/off power cable unit.
I had used my sprayer the first time, put it back in the workshop, out of the sun, no critters chewing on cables, etc. Came back to use it the second time, and that little on/off box had somehow failed, and I could't get the sprayer to turn On. Hours and Hours of troubleshooting, going back and forth to Northern Tool, buying replacement motor, etc. All it turned out to be, was a faulted On/Off power cord, after one use! For the money, $20 or so, keep one of those as a spare on-hand...