Not all batteries are the same, and they all require different amounts of current to recharge them. Even though power banks can usually charge batteries of all smartphones irrespective of their specific capacity, they are not always suitable for low-power devices like Fitbit bracelets, Apple Watch, Bluetooth. While trickle charging is a handy feature for charging small devices, the technology behind it is quite fascinating. Here are the two main technical components that enable low-current charging: There can be several different reasons why a power bank might not be able to charge low-current devices: Minimum Current Threshold: Power. Despite the convenience of trickle charging, you might sometimes face challenges in getting it going. Here are some ideas that might help you troubleshoot some of the. Some power banks have a built-in low-current charging feature, but you will need to enable it first. Follow these steps to enable it. 1. Connect one.