Nima can be charged using the USB charging cable that comes with it. Nima takes approximately 90 minutes to 2 hours to fully charge (if you're starting with a completely dead device). Nima can perform 20 or more tests after each full charge.
Nima doesn't ship with its own wall-charger, but you can use the included USB charging cable with any compatible USB power-source like the USB port in your car, on your computers, or other USB wall-plugs. Please note that, Nima cannot be charged with a USB cable meant for an iPhone or iOS device.
Battery life does vary, though, and your personal device's battery life will depend on the number of tests you run, how often you sync with your phone, and how frequently you charge it.
Each Nima contains a 320mAh LiPo battery, similar to the kind used in smartphones and other mobile devices.
Portable chargers, battery packs, and cells are safe to use with Nima as long as they have a micro USB plug (the same as are found on most mobile phones). Please note that, though Nima's charging cable looks similar to those for iOS devices, iOS device charging cables will not work with Nima.