<you asked> ....HMMMM Is there a disadvantage with a Variac charger?
Variac (transformers) are non-isolating. On the other hand, you can *control* the voltage (current) output with an optional motor drive to position the knob (output voltage). I believe the motor drive is *controlled* with a CT (current transformer) and user-settable *pot*. It's been a while since I've worked with these, but check your local industrial electronics suppliers for their motor- controlled variacs (or Staco at http://www.variac.com/staco_Variable_Transformer_Map.htm or maybe Superior Electric) Jim Waite
