Power bank
A power bank is a mobile additional battery, especially for smartphones and tablets ; larger ones also supply notebooks. It is a mobile energy storage device with a switching converter that provides a constant output voltage, usually 5 volts.
General
The advancing miniaturization and the development towards ever flatter mobile end devices are placing technical limits on the capacity of the batteries that can be integrated into the devices . In order to extend the useful life of the devices, there are additional, externally connectable memories.
Technical
A power bank is usually equipped with one or more lithium-ion battery cells , so taking it on the plane is conditional due to the risk of fire. It contains a switching regulator to stabilize the output voltage and current limitation as well as often LEDs to indicate the operating or charge status . The power is supplied via one or more USB ports (usually type A), the power bank is usually charged via a micro USB port . The possible charging and discharging currents are not standardized and can deviate from the USB specifications. Therefore, not every power bank is suitable for Apple devices or it only works with a proprietary charging cable from this manufacturer. Some power banks have two or more outputs, one of which is often dedicated to iPhones or iPads.
Power banks with other outputs, e.g. B. for FireWire or Thunderbolt , would be technically possible, but are not found in practice.
The batteries in power banks with USB output have capacities (= amount of electrical charge) between under 1,000 mAh and over 20,000 mAh. The information relates to the built-in battery, not the electrical energy that can be drawn, because the battery voltage must be increased from 3.7 volts to 5 volts and the efficiency of the switching converter subtracted. In addition, the information is often clearly too optimistic. This results in a real energy storage capacity of approx. 3 Wh to 70 Wh. (For comparison, a light electric vehicle such as the Renault Twizy provides 6,100 Wh with its cells.) The maximum current can be between 500 mA and over 3 A. vary.
For laptops, however, correspondingly larger devices are offered that can be connected to notebooks with the usual voltages of z. B. supply 12 V or 19 V.
Additional functions
Only power banks that can be charged and discharged at the same time are suitable as backup batteries .
In practically all models, the output is switched off when the output current is too low, which can be prevented with a small circuit.
A built-in flashlight or the digital display of the charge and operating status can be part of the comfort equipment.
There are high-current power banks that can be used as a dedicated or additional function to help jump-start cars, but fail at temperatures below freezing point, because lithium batteries, unlike lead batteries, are very sensitive to cold.
Web link
Individual evidence
- ^ A b c Rudolf Opitz: Mobile power plants. In: c't . 2020, accessed on July 29, 2020 .
- ↑ Moritz Jäger: Buying advice on power banks: Refuel on the go. In: heise online. July 21, 2020 .
- ↑ Michael Nowak: Base load for power bank. January 29, 2020 .
- ^ Hans-Heinrich Pardey: Powerbank: Reserve tank for smartphones and tablets . In: FAZ.NET . ISSN 0174-4909 ( faz.net [accessed November 20, 2018]).
- ↑ Test Start Booster. In: ADAC. January 19, 2016 : "None of the products tested meets its performance specifications at -18 ° C, only one at 0 ° C."