Herk...while I agree with everything else you say, I'm struggling with this statement.
The ideal charging amps for FAST charging bulk/absorbtion for the typical 80 to 100amphour battery...is 16 to 20 amps. Running a 6 amp charger will take a LOT longer generator run time.
The ideal generator to put out 20 amps @ 14.4 volts... is 288watts...so you don't need a 700 watt generator to simply charge the battery. If you want to do more with the generator 700 may be fine or not enough if you want to power a lot of stuff.
I like the recommendation of a separate battery charger from the genny...but something like an Iota DLS20 with IQ 4 stage charging would be a much better choice IMO. If a portable unit is desired...then http://www.amazon.com/SOLAR-PL2320-P...productDetails
is a good value with automatic multistage charging.
EDIT: Just noticed your post is over a month old...Duh...no need to reply unless you feel like it!