5 reasons why your power bank is charging slowly (even with a fast charger)

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Whether you’re out of power, making a short layover at an airport, hiking all day on a famous trail, or camping for days in the wilderness, a power bank can give your phone the extra juice it needs to see you through the situation. It can also ensure that your phone does not turn off in an emergency. But if the power bank charges slowly when plugged into a wall outlet, it can leave you vulnerable when you need it most.

One thing that causes a power bank to charge slowly is if you don’t have the right equipment. For example, if you need to charge it quickly, it’s a good idea to use a fast charger. But if it happens while using a fast charger, it might be due to some bad charging habits like charging and discharging the power bank simultaneously or using it in extreme temperatures.

However, if none of the reasons mentioned below are causing the problem, it could be a mechanical fault that is difficult to repair. If the external battery is under warranty, it is best to return it for repair. But if charging is slow and you notice it has a bulge, the lithium-ion battery inside may pose a fire hazard and should be discarded.

A high-capacity power bank has a capacity of 10,000 mAh or more. Those with a capacity of 20,000 mAh or more and a power of 45 W or more can even charge some laptops. In addition to having a high efficiency, most of these power banks can be charged quite quickly using a fast charger. If you use a low-power charger that produces 5 to 10 W, like those supplied with cell phones, the power bank will take much longer to charge.

For example, something like the Juovi Power Bank 45W 20,000mAh Portable Charger requires a charger that produces 45W or more to fully charge in two hours. To achieve this speed, you’ll need a high-power power adapter like the Anker 45W USB-C Charger Block, which will cost you $30 more (you get two USB-C chargers and cables in the box for that price). The charger doesn’t have to be exactly 45W. Even if it’s a 120W fast charger, it won’t fry the power bank because the two will communicate and negotiate safe charging levels using the Power Delivery (PD) protocol. The power bank will only consume the power it needs (nothing more).

If you are using a fast charger and notice that the power bank is still charging slowly, you may be using the wrong USB cable. For example, using a low-power USB cable rated at just 15W may slow charging if you’re using a compatible wall adapter. Try a USB-C to USB-C cable designed for fast charging, as it can transmit up to 100W. A good example is the Soopii 100W 4ft USB-C to USB-C Fast Charging Cable. It costs $10 and even has a status indicator that shows how many watts it’s currently putting out.

If you are using the correct USB cable and charging continues slowly, you may have a faulty USB cable on your hands. To quickly rule out this problem, try a different cable and see if it charges as expected. If so, check the USB cable for fraying, which can happen if it is frequently bent, twisted, or pulled at the connection point, where it is most vulnerable. If it is still intact, the internal copper wires may be broken. Either way, you should think about replacing it and taking better care of the new USB cable you receive.

Modern power banks feature pass-through technology that makes them capable of charging and discharging at the same time safely. With pass-through, the external battery has the necessary circuitry to separate the charging and discharging processes. It makes sense to take advantage of this feature, especially when you’re traveling, and you need the power bank and your devices charged once you find an outlet during a quick stop. However, this splits the current, resulting in slower charging rates for the power bank and the device being charged.

Additionally, the more devices you plug in, the slower the charging process will be. Just because a power bank is rated at 45W doesn’t mean all connected devices will charge at the same 45W speed. In reality, the power will be split between the ports and the power bank’s lithium-ion battery. What you can do at this point is unplug all devices and see if the power bank starts charging at the expected speed. If it works, let the power bank fully charge so you can quickly remove it and start charging your other devices.

Slow charging can sometimes be the result of dirty ports. When you don’t clean your power bank’s USB ports, dirt and other debris (pocket lint, food crumbs, and skin oil), as well as moisture from sweat and humidity, can clog or oxidize the ports. This can result in contact resistance, causing symptoms such as slow charging, frequent disconnections, and refusal to connect. The USB ports are very precise, which means that the contact they make with the charging cable must be unrestricted for the current to flow properly.

The same tips for cleaning a computer’s USB ports can work here. You can use a soft-bristled toothbrush to gently sweep away any debris before it has a chance to settle. If it is particularly stubborn, you can use a can of compressed air to remove it. Avoid using household cleaning products, as they can cause the USB ports to short circuit and lead to corrosion that could affect the internal components of the power bank.

If the USB ports are not blocked, look for signs of damage. If you notice any issues like broken pins or cracks, it is best to take it to a repair specialist or simply replace this power bank completely.

Power banks like Cuktech 10000mAh Magnetic Power Bank are equipped with a sensor called negative temperature coefficient (NTC) sensor. It monitors the external battery’s temperature during the charging process to protect the battery if it gets too high (above 113°F). When the protection is triggered, the external battery reduces its charging speed to avoid generating additional heat until the temperature returns to an ideal operating level.

Although some heat is expected from the charging process, factors such as placing a power bank under a pillow, leaving it in a hot car, or using it while charging can cause it to heat up more than normal. This protection is necessary because if the lithium-ion battery overheats, thermal degradation can occur, reducing its lifespan. In rare cases, this can result in thermal runaway, a chain reaction that can lead to fire or explosion.

Sub-zero temperatures are also a problem, as they can slow down the battery’s internal chemistry. This is why a power bank may charge slower than normal when exposed to freezing cold. If the external battery is left exposed to extreme cold for too long, the battery may freeze. If you try to charge a frozen lithium-ion battery, you can cause permanent damage due to a degradation mechanism called lithium plating. This is where small pieces of lithium metal stick to the negative electrode of the battery, decreasing its capacity.