if its a parallel mech then it should work with both + ends into the mod. if you did it in series either side combo, it should have gotten nasty since it would have been a direct short as soon as the base plate was installed.... if its a series mod and the batteries were put into it in paralell manner, there is a slight chance it could have worked if there was an imbalance in voltages between the batteries... but still not a good situation for a length of time
