Power bank not charging or draining fast: when it is still safe to use

Unplug the charger and switch the device off. Never puncture, bend or heat a swollen battery.

Put the power bank on a hard, non-flammable surface while you check it, and never charge it unattended.

Most power banks use four small lights to show the charge level and status. The Xiaomi Power Bank 3 manual describes a common pattern: while the power bank charges, the lights blink according to the charge level and all four stay on when it is full. If all four lights blink together, there is a charging error.

Two things are often mistaken for a fault. First, the button on a Xiaomi power bank is a battery level check button, not a power button; the power bank detects on its own whether it is being charged or charging another device. Second, the indicator lights turn off on their own about two minutes after the charge runs out. Lights that are off do not mean the power bank is broken.

Anker gives three simple first checks: try another wall charger, another cable and another wall outlet. Anker also names a dirty port or bent connectors as a cause, and suggests cleaning the port with a dry, soft tool.

If no light comes on at all when you press the button, the Xiaomi manual says the power bank may be in protective mode. Plug in an external charger to bring it back. A power bank left unused for a long time can drain down into this state.

Charger power also affects charging time. Xiaomi writes that the Power Bank 3 charges fully in about 4 hours with a 9 V/2 A or 12 V/1.5 A charger, and in about 6 hours with a 5 V/2 A charger. An old, low-power charger makes a power bank look as if it gains no charge even after hours plugged in.

Xiaomi also asks for a charger that meets local safety standards, to prevent electric shock or battery damage. If a no-name charger gets very hot in use, stop using it.

If the power bank still has charge but the phone does not charge, Anker suggests trying another cable that is known to work. Also try another device, to find out whether the problem is the power bank or the phone. Xiaomi asks you to check whether the device being charged shows a charging icon, as a sign that the power bank is working.

TWS earbuds, smartwatches and fitness bands only draw a small current. For devices like these, Xiaomi offers a low-current mode: while the power bank is not being charged, press the battery level check button twice. The lights come on one by one to show the mode is active. Press once more to exit; the power bank also exits the mode on its own after two hours.

The big mAh number on a power bank is the capacity of its battery cells, not the amount of charge that reaches your phone. The Xiaomi Power Bank 3 specifications show the difference clearly. Its cell capacity is 10000 mAh at 3.7 V, while its rated capacity is 5500 mAh at a 5.1 V output. Some energy is lost when the voltage is stepped up and when the phone charges its own battery.

So a 10000 mAh power bank will not fill a phone with a 5000 mAh battery twice. If it used to charge your phone almost twice and now only manages half, the power bank's battery capacity has dropped. Xiaomi names a sharply reduced capacity as one of the reasons to stop using a power bank.

Storage matters too. Xiaomi suggests storing a power bank you will not use for a long time at about 25 to 50% charge, in a cool, dry place, and not leaving it full or empty for long periods.

The indicator lights may show a wrong level, or the power bank may behave oddly and seem dead. For that, Anker describes a reset: plug both ends of one cable into the power bank's input and output ports at the same time for 3 to 5 seconds. After that, charge and use the power bank as usual to see whether the problem is gone.

For the PowerCore 20000, an article on the Anker website gives a longer time. Connect the Micro input and USB output ports with the supplied cable for around 15 seconds, then disconnect once the lights stop flashing. The reset method differs between brands and models, so follow the instructions for your power bank's brand. If the manual does not mention a reset, simply charge the power bank fully with a suitable charger.

The Xiaomi manual has a list of don'ts that fit everyday use in Indonesia:

• Do not charge the power bank or use it to charge a device in a pants pocket, a closed bag, or on a bed or sofa, because the heat gets trapped.
• Do not stack the power bank and the phone on top of each other during a long charge.
• Do not leave it in a car or anywhere else in direct sunlight in hot weather.
• Keep it away from pressure, impact, strong vibration and liquids, as well as heat sources such as a stove and room temperatures above 60°C.
• Do not leave it unattended while charging, and unplug it before you go out.

Anker adds a few care habits: charge the power bank every three months even when unused, use a suitable cable, and avoid running it down to empty again and again.

Xiaomi asks you to stop using a power bank at once if its case swells, deforms, starts to leak, or its capacity drops sharply. The same applies after it has been under pressure, taken a hard knock or gotten wet. Anker adds other signs: the power bank gets very hot during use or charging, its lights die completely, or it runs down quickly even when unused.

• Unplug every cable and put the power bank on a hard surface, away from anything flammable.
• Do not charge it again to test whether it still works.
• Hand it to the brand's authorized service center or an e-waste collection point. Do not throw it in the household trash.

Xiaomi states that the power bank casing must not be opened under any circumstances. Opening the battery pack, taking the battery apart or replacing the battery cells is not a job for home. For a power bank it is usually not done at all; a failed unit is replaced with a new one.