This power bank is very good at what it does. The 10,000 mAh capacity power bank has a healthy 5-cell battery. There’s a built-in chip that monitor’s voltage output and shuts down if the voltage exceeds the maximum limit. You will never overcharge your phone with this power bank. This power bank is very good at what it does. The 10,000 mAh capacity power bank has a healthy 5-cell battery. There’s a built-in chip that monitor’s voltage output and shuts down if the voltage exceeds the maximum limit. You will never overcharge your phone with this power bank.