I'm not a DA guy, just try to read up on the posts about them since I may give them a try one of these days, but IIRC there are some voltage input considerations for DA. A fully charged 6 volt Ni-Mh can put out more than 6 volts so you may want to verify what the module will take for input voltage.
I know that the older style modules used on my ZDZ's were restricted on input voltage, but the new 100 I have can run off unregulated Lithiums with an input voltage range up to 9 volts.
Maybe you've already checked that, or some of the DA guys will check in on the voltage input question?
Looks like some others who know more about it than me checked in while I was typing...