Almost all power bank you can buy today come with some sort of short circuit protection mechanism. You may have seen it on an actual device, advertised on a product sales page, or listed in the user manual. Although the name is pretty intuitive, let’s explore short circuit protection features to better understand how they work.
What are short circuits
An electrical short circuit is an almost non-resistant connection of the two poles of an electrical voltage source, or generally of two circuit points with normally different potentials, whereby the voltage between these parts falls to a value close to zero. This type of event can lead to an increased supply of current to flow uninterrupted, thus causing damage to the circuit itself or to other devices connected to the circuit.
In batteries, short circuits happen when the positive terminal gets into direct contact with the negative one. As a result, the battery starts dumping current into itself, creating a lot of heat in the process. The heat can damage the battery circuit leading to leakage, fire, or even an explosion. Most of the time, after a short circuit, batteries get damaged and will become unusable.
Short circuit protection in power banks
The shortcut protection mechanism checks the value of the current over time. So, if the current reaches a certain level, it switches to a circuit that has more resistance, in order to lower the current. Or, if it can’t stop the current increase, it can turn off the whole circuit.
Here’s a diagram of what a short circuit protection mechanism might look like in a power bank:
In the undisturbed “normal operation”, Transistor V1 conducts the current. After a short circuit is detected, this transistor is switched off so that a limited overflow can flow over V2 and the resistance R. After the short circuit has been clarified, i. e. after the consumer side protective device has been activated, the current returns to its normal range.
The V1 can then be switched on again so that the original, undisturbed operating state can be adjusted again. However, if it is not possible to achieve a short circuit declaration within a defined time, the current must be completely interrupted by switching off V2 in order not to overload the current limiting resistance R2. The freewheel diode V3 then takes over the current until it has completely disappeared.
Depending on the load capacity of the current limiting resistance, it is now possible to try once or several times to achieve the short-circuit declaration by repeatedly switching on the V2. If this also fails, the battery must remain disconnected from the grid after switching off V2.
Do all power banks come with short circuit protection?
Yes, of course, all come up with a short circuit protection feature. As a matter of fact, short circuits can be highly dangerous if they happen in batteries, as they can even cause explosions. For this reason, power bank manufacturers take short circuit protection very seriously and they integrate such mechanisms in their devices.
However, if you were to purchase knock-off power banks from no-name manufacturers, then you might be surprised to find that the devices lack a short circuit protection safety feature. We covered some other disadvantages of buying knock-off power banks in this article.
Although short circuits can be quite dangerous if they were to happen in a power bank, this is a highly unlikely scenario as the vast majority of them come with shortcut protection features. So there’s nothing to worry about. However, you might get unpleasant surprises if you were to buy low quality portable chargers.