Small Engine Troubleshooting Problems? Ask a Mechanic Now.
Voltage needs to be over 12 volts, will the battery start the tractor without help? If so it is not a voltage problem. I would check the seat switch and harness. The mower thinks there is no one in the seat, so when you engage the blades, it kills the engine. You say it stalls the motor, or does it cut off like key is turned off?
Did you get it to work?