Have you ever found your mobile phone low on power at a critical moment? For example, when needing to use GPS navigation in an unfamiliar neighborhood and waiting 3 hours for your phone to charge is not an option. We’ve all been there. Besides ensuring you have a full charge on your phone before going into a situation like this, the next best solution is to have a power bank on hand with fast charging capabilities.

The principle of fast charging is simply to increase charging power (P). According to the formula P (power) = V (voltage) x I (current), there are three ways to increase the power.

What is Fast Charging?

The easiest way to increase power is to increase current. This equates to using a larger pipe to move water from a container to another faster, as illustrated with container A and B below. However, it is impossible to enlarge a water pipe endlessly, so there are limitations to this method.

1. Increase Current (I)

Going back to the water containers, when you can no longer enlarge the water pipe the next best thing to do is increase the amount of water in container A. In terms of charging this means increasing voltage, for example ramping up to 9V 2.0A to deliver 18W of power, compared to 15W provided by 5V 3.0A. But keep in mind, a phone will only take in as much power as its charging circuit is designed for. So even if you have it plugged into a 9V 2.0A adapter, if it's only able to handle 5V 3.0A, that's the rate at which it will charge. For fast charging to work, you need a phone or other device with a charging circuit capable of using one of the fast charging standards.

2. Increase Voltage (V)

When voltage is dynamically adjusted for charging, the voltage can be adjusted slightly according to the state of the device / charger / charge line, which has the advantages of providing both higher current and voltage

3. Dynamic Boosting of Voltage (V) and Current (A)

Lithium-ion batteries or polymer batteries used in power banks are susceptible to damage or combustion due to problems in the circuit conversion process. Luckily, there are a number of protective mechanisms to ensure your safety. They include:

Security protection mechanism

Over-voltage / over-current / over-discharge protection: Over voltage and current protection disables charging when the battery voltage and current goes above a safe threshold and over-discharge protection disables discharging when the battery voltages goes below a threshold.

Short-circuit protection: Short circuit protection disables discharging if a short circuit is detected. 

Input overvoltage / overcurrent protection: when charging the power bank in reverse, if the input is too high or exceeds the set voltage or current, the power bank will disable charging.

Over-temperature protection: Whether charging a power bank or device, the charging is disabled when the battery temperature is too hot or cold.

The more of these mechanisms a power bank has the better. The above mechanisms not only ensure the safe use of standard power banks, but also for those featuring fast charging technologies.