There is a whole list of things that could be causing your voltage to drop shutting off your helix when you start the big motor, but if you push the power button on the helix and let off you will see a drop down that has a standby tab arrow down to it and arrow right and the screen will go black. Start your motor then push the power button in the helix and it will come right back to the screen you were on. Have someone hold a multimeter on your battery while you crank it and see what your voltage drops to while cranking it.
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