Just to offer some info to those with problems and in particularly battery issues. I have been looking into this board with a view of building a mod for myself....here is a link to the DNA data sheet.
The item on the board that Mawsley referred to is in fact a fuse, the details about which are found within the pdf document. It is there to prevent reverse polarity damaging the board....just how some Chinese person connected a one way only idiot proof terminal who knows? But hey, here it is if it helps shed light for anyone.
http://www.evolvapor.com/DNA200/DNA 200 data sheet.pdf