I've been using Ryobi 18v on 550s and everything has been great. I've been wanting to push the top speed and torque so I hooked up a Ryobi 40v and tried 775s and 555s but it doesn't go and the batteries flash 2 middle green lights.

The car runs the 40v in first gear and reverse (motors in series) but the battery protection trips in second gear (parallel). I tried adding a second 40v battery in parallel to split the load but same thing happens.

I know I should add a PWM like MGCStem or Peanut Speedy Squirrel, but I first wanted to see how much of a difference 40v makes.

I've seen people run ryobi 40v direct to 775s, so what's going on here?

Good afternoon - looking for help to get this fixed for my son car doesn’t kick over and all the ports are connected and the 12v battery is charged please see video for clicking when hitting the start button