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How does a power bank, the small portable device for storing electrical energy, work? It’s best to think of it as a mobile power socket
How does a power bank work – how it works, structure, components and performance
A power bank is a portable charger with a robust and often compact housing that protects the internal components and makes the power bank portable. It is used to power electronic devices such as smartphones, tablets, laptops, smartwatches and other devices with a USB port on the go. The power bank serves as an external battery that stores electrical energy and can deliver it to other devices when needed.
- The power bank offers a convenient way to charge devices when traveling, during outdoor activities or in emergencies. It serves as a reliable backup power source when there is no power socket nearby. For this to work, it is first charged via an external power source. LEDs indicate the charge status of the power bank
- The charge controller ensures that the current flows evenly and safely into the cells. The current is stored in the internal cells. Most power banks use lithium-ion (Li-Ion) or lithium-polymer (Li-Po) batteries. These have a high energy density and efficiency. Li-ion batteries are cylindrical or prismatic, while Li-Po batteries can be manufactured in more flexible shapes.
- Charging and discharging regulators are circuits that control the flow of current so as not to damage the batteries during charging and discharging. Integrated protective circuits prevent overcharging, deep discharging, short-circuiting and overheating. The charge controller and discharge controller share the work as follows: The charge controller regulates the current flow when the power bank is being charged, while the discharge controller ensures constant and safe charging of external devices.
- The power bank itself is usually charged via a micro USB, USB-C or Lightning connection. An external device such as a smartphone is connected to the power bank via a USB cable. Most power banks have USB-A or USB-C connections. The connected device is charged by converting the stored energy from the power bank into electrical energy and transferring it to the device.
- The capacity of a power bank is specified in milliampere hours (mAh) and determines how much energy it can store. A higher capacity means that the power bank can store more energy and therefore charge more or larger devices. However, not all of the stored energy can be used, as some is lost through heat and circuit efficiency. The efficiency is typically between 80 and 90 %.
- The charging time required to fully charge the power bank depends on the capacity of the power bank and the power of the power source. Higher power sources charge faster than lower ones. In addition, modern power banks are equipped with several protection mechanisms. Overcharge protection, for example, prevents the battery cells from being charged beyond their maximum capacity.
- The deep discharge protection prevents the battery cells from falling below a critical voltage, while the short-circuit protection prevents damage caused by short circuits and the temperature protection prevents the battery cells from overheating during the charging process.
Which model for which purpose
There are various models of power banks that differ in several aspects. These include capacity, output power, connections, charging speed and additional functions. The wide variety of power banks is tailored to different needs and applications. Choosing the right power bank depends on individual requirements.
- If capacity is the most important factor, the first question to answer is the desired electrical current. Key ring power banks, for example, have a low capacity of up to 5,000 mAh and are therefore suitable for emergencies, for example to charge a smartphone once.
- Most users use standard power banks with 5,000 mAh to 10,000 mAh. They offer a good balance between portability and performance. They help with charging a smartphone once or twice or charging a tablet once.
- If you are looking for a power bank for (multi-day) outdoor activities, it is best to opt for capacities of 10,000 mAh to 20,000 mAh and above. These power banks are larger and heavier, but can charge multiple devices, including tablets and laptops.
- Another point to consider when purchasing is the output power. Basic models already meet simple charging requirements, for example to charge a smartphone or watch. However, if you constantly need to charge modern smartphones and tablets, it is better to use fast charging technologies such as Qualcomm Quick Charge or USB Power Delivery.
- When it comes to connections, USB-A is sufficient to use standard power banks. USB-C ports often support fast charging functions. The connection is ideal for newer devices with USB-C plugs. Older or inexpensive power banks have a micro USB port. However, the standard is becoming less and less common on new models. Apple users use Lightning as input or output on many models.
- Sometimes size matters. If you want your power bank to fit in a jacket pocket, reach for the ultra-compact key fob. Handbag or briefcase-friendly models are ideal for everyday use. For longer trips, there is no getting around large-format power banks. Although they are larger and heavier, they offer much more energy and additional functions.
- Solar power banks have integrated solar panels. They can be charged by sunlight and are therefore ideal for campers or hikers. If you don’t fancy cables, you can opt for a power bank with Qi charging function or a power bank with built-in cables. Large power banks usually offer several outputs so that smartphones and tablets can be charged at the same time.
- Basically, the following types of power banks can be distinguished: Standard power banks, which are used for smartphones and tablets. Fast-charging power banks that charge devices in a short time. Solar power banks with integrated solar panels that enable charging by sunlight, and laptop power banks with higher capacity and special connections
