Looks like it is a 12VDC variable speed humidifier. Did you see that fuse on the control board? And, it looks like he's driving it with a 7Ah 12V batt. That's 7000 mAh. Eat up a 2000mAh batt pretty quick.....

77mm High (about 3"), 72mm Wide (about 2 3/4" ), and 110mm Long (almost 4 1/2"). Won't fit in my Tiger I.

But sure is a sweet idea (provided the tank doesn't get upset with you for pouring water inside it).

Splat