In theory you could... However, after some time in use the dehumidifier gets "Stuff" on the evaporator fins. That is dust, biologicals (bacteria, etc) and other contaminants in the air stream. The water will be soft compared to
drinking water, but I'm not sure I would put it in a
battery. Distilled water is preferred, deionized water will
work. Deionized DI process removes almost everything but dissolved organics. Distilled removes everything....