Ben, I do get there are three measures of a charger: voltage (kV), energy pulse (joules), along with the time/shape of the pulse that makes these things work.

It is the combination of these that keeps them from killing us also. Different manufacturers combine these in differerent ways.

kV is cheap to provide. Joules are expensive to provide. Time/shape of the pulse takes engineering and is a major part of the difference between different manufacturers' units.

That's all I know about chargers.

Jim at Dawn