All USB cables are not created equal. It’s best to use the cable provided with your FieldKit. Failing that, use a heavy duty cable made for high current charging to reduce voltage drop. If you’re having trouble getting your FieldKit to charge over USB, the cable should be the first thing you try changing. FieldKit has been tested using Anker and Monoprice charging cables with success.
USB wall chargers are built in a wide variety of qualities and capacities, not all of which are adequate. FieldKit is tested using Anker brand chargers, and the use of high-quality, brand-name dedicated chargers which are not supplied free with other products is encouraged.
The use of USB battery banks is sometimes effective, but many of them, when presented with the low power draw of a FieldKit, presume there is nothing connected and stop providing power after a bit, so if you plan to use a battery bank with FieldKit, test thoroughly. We do not yet have a battery bank that we can recommend without reservation, but as we continue to test we will keep our documentation updated.