Under-powering a digital device can sometimes have pretty nasty consequences. Brown-out conditions can cause memory to get written or overwritten in odd ways, can cause unexpected behavior in connected systems and just generally screw up your day. One way to avoid this is to keep an eye on your battery voltage and turn off the system before it gets too low (or plug it in). We've whipped up a little board to help you out with this situation: the "Uh-oh" battery level indicator. Project description, more information and ordering can be found at https://www.sparkfun.com/products/11087 Datasheet: http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Kits/TL431-D.pdf Arduino Connection: http://dlnmh9ip6v2uc.cloudfront.net/datasheets/Kits/DSC_0001.jpg