Maybe I just got a bad unit, but my batteries ran out after only a few hours of use. The memory unit runs on two type CR2032 batteries. Now, the problem with this is that these batteries are so expensive that replacing them costs about 3/8 the price of the VMU. Kinda expensive if you ask me. It is still a great idea however, and I recommend picking at least one up. I have a few games for Dreamcast and they would have been somewhat less enjoyable without the unit. I just hope your batteries last longer than mine did.