RE: [CAD_CAM_EDM_DRO] Batteries in Power Supply

Whether this works depends on part on what type of batteries they are (you
didn't mention).
NiCd and NiMH batteries turn overcharging into heat, possibly causing the
batteries to explode.
Lead-Acid batteries turn overcharging into hydrogen and oxygen possibly causing
the air in and around the batteries to explode.

The "slow" NiCd and NiMH chargers prevent battery explosions by limiting the
charge current, which is why they take so long to charge.
The "fast" chargers do one of two things: The use custom battery packs which
contain a thermal sensor (e.g. Makita cordless power tool batteries) or they
look for a specific blip in the cell voltage as the cell reaches full charge.
For NiMH batteries, once the blip is reached, the batteries continue to generate
some heat internally *even when you remove the charging current*

You could adjust your input voltage to use voltage-limiting to avoid
overcharging the cells, but it is not clear whether the cells will "learn" their
new customary charge level and still be subject to occasional overcharging (say,
when your house line voltage goes 2% higher for some reason).
-Kevin Martin