For DIY enthusiasts in the green energy community, homemade lithium-ion battery packs have long been a holy grail. For everything from home solar energy storage to garage-built electric bicycles, ...

I have an APC Smart-UPS 3000 XL battery backup. In addition to the internal batteries, it has a connector for adding an external battery pack to it. While it's available on Newegg for WAY cheaper than ...