I think what they are fussy about is the idea that you will fine tune when the light comes on, and they have some elaborate procedure for calibrating when that light comes on... When you have a 6V SLA that light is your "gas guage". On a DVD player battery they have their own fuel gage, so it doesn't matter.
To whomever complained about having problems with the proper switchcraft connector and preferred the ratshack connector.... there are multiple Switchcraft numbers, like 765 and S765, one is .100 ID and the other is .080 ID... the one with the .100 ID doesn't work well, I've got one of those too.