RE: Voltwatch, you all use 'em?
The "Voltwatch" is for 4-cell (4.8V) NiMH and NiCd packs only. The "Voltwatch2" has a tiny switch on the side to select between 4-cell (4.8V) and 5-cell (6V) packs. There is also a "Voltwatch 12V Field Power" unit that is for monitoring 12V field batteries for your starter/charger. They are all labeled clearly and look quite different (see photos below):