Hmm. I think my 60CSx only has options for NiMH and alkaline. Maybe there is a flash update -- I'll have to check.
FWIW, both my GPS III+ and eTrex Vista have options for lithium cells.
Recently I've read that Garmin is changing the DVD software so that it can only be used on one unit, which makes the choice of DVD vs. the MicroSD kind of a mute point.
That stinks.
While I haven't looked lately to see if it covers TENERGY batteries sepecifically, I consider
this the authorative reference for NiMH batteries.
-john