Have you got anywhere with this? I’m attempting to do the same thing with two 5Ah 20V dewalt batteries. If you used 18V batteries then it may have a low voltage cut off. The voltage might have to be 1 or 2 volts from 40V in order to work. My Helix 7 won’t turn on if the voltage is 21V But it will turn on at 18 to 20V. I currently run it on 2 5Ah dewalt batteries.

Have you got anywhere with this? I’m attempting to do the same thing with two 5Ah 20V dewalt batteries. If you used 18V batteries then it may have a low voltage cut off. The voltage might have to be 1 or 2 volts from 40V in order to work. My Helix 7 won’t turn on if the voltage is 21V But it will turn on at 18 to 20V. I currently run it on 2 5Ah dewalt batteries.