The Hidden Dangers of Hot Swapping

Hot swapping is the function of inserting or removing components or devices from electronic equipment while it is operational. This feature allows users to replace or upgrade hardware while the system is running without the need to shut down or restart the entire system. However, hot-swapping batteries is actually a very dangerous action that can easily damage the hardware if not properly protected. This article will discuss this issue in detail and provide solutions to eliminate circuit hazards and improve the reliability of product functionality.

Hot swapping actions often cause significant current or voltage fluctuations. Voltage fluctuations occur because the inserted or removed component is in an unstable state when making contact with the circuit, while current fluctuations result from the capacitive characteristics of the component's low equivalent series resistance (ESR). Regarding voltage fluctuations, they can usually be compensated for in design by increasing energy storage devices, improving the circuit's voltage compatibility range, and other methods. However, protection against current fluctuations is often overlooked in engineering design. When hot-swapping modules with low ESR, the momentary circuit contact is equivalent to a short circuit to ground. In many applications, this momentary current can even reach several hundred amperes.

From this, it is evident that the risks of hot swapping primarily involve surge currents and oscillating voltages. As mentioned earlier, surge current is an exceptionally large instantaneous current caused by the presence of parasitic circuit parameters. Oscillating voltage occurs when surge currents appear on PCB traces, where even small impedance can cause significant voltage variations. The longer or thinner the traces, the greater the voltage amplitude.

In summary, we need to pay more attention to the issue of hot-swapping batteries due to the following reasons:

• Batteries are one of the most common hot-swappable components, and we often instinctively hot-swap them.


• Batteries have very low equivalent impedance, so once surge currents occur, they can be quite severe.

Protecting against surge currents requires taking measures at the source, which involves adding protection between the hot-swapping point and the backend circuitry. In some simple protection circuits, commonly used components include ferrite beads and magnetic rings. They can significantly suppress surge currents but may worsen oscillating voltages because they introduce inductance into the circuit, causing additional induced voltages. Currently, the more reliable method is to use complex components. In engineering design, there are two common types of surge current protection circuits: those constructed using discrete devices and those utilizing dedicated surge protection chips.

Our WMR2387 uses the hot-swappable function, the two batteries have a total power of 13600mAh, and have passed CE, FCC, CB, UL60601-1 and other certifications, so that you can continue to use the product safely without plugging in the power , and replace the battery at any time.

Check out MACTRON GROUP(MTG)’s brand new WMR2387. Our Medical Rechargeable Touch Panel PC can show outstanding performance in any medical field, and provide you with safe and powerful services. It can meet all your imagination.