▷ Motherboard battery: what is it and what is its function

Whether you are using a desktop or laptop PC, your device's motherboard contains a fairly large button-type battery. Unlike the battery of a standard laptop, the battery on the motherboard does not power the PC while you are using it. In fact, quite the opposite, since the battery is small and is only active when you are not using your PC.

Index of contents

What is the motherboard battery and why is it important

The motherboard battery is generally a CR2032 lithium coin cell. This type of battery, contrary to popular belief, is not rechargeable and trying to do so can cause an explosion. Motherboards have circuits that prevent batteries from charging and discharging when the PC is turned on. Other common types of battery cells can last significantly longer or shorter periods, such as the smaller CR2016, which will generally last approximately 40% less than the CR2032. Higher temperatures and longer shutdown time will shorten battery life.

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By replacing the battery cell, the system time and CMOS BIOS settings may revert to the default values. Unwanted BIOS reset can be prevented by replacing the battery cell with the PSU's power switch turned on and plugged into the wall outlet. On ATX motherboards, by turning on the PSU's power switch, 5V backup power is supplied to the motherboard to keep the CMOS memory energized during the shutdown period.

While most motherboards have a place for a CMOS battery, some smaller PCs, as well as many tablets and laptops, have a small external CMOS battery compartment that connects to the motherboard via two small cables.. Some devices that use CMOS include microprocessors, microcontrollers, and static RAM (SRAM). It is important to understand that CMOS and BIOS are not interchangeable terms for the same thing. While they work together for a specific function within the PC, they are two completely different components.

Battery functions on the motherboard

The motherboard battery is used for low-level system functions, such as powering the real-time clock and storing the BIOS settings of a PC. On newer PCs, the battery can only be used for the watch. Traditionally, BIOS settings were stored in CMOS RAM, which was powered by the battery when the PC was turned off. The stack was necessary because the configuration would be lost if all power was lost, just as data in RAM is lost when power is lost. CMOS stands for complementary metal oxide semiconductor. CMOS is sometimes referred to as Real Time Clock (RTC), CMOS RAM, Nonvolatile RAM (NVRAM), Nonvolatile BIOS memory, or Complementary Symmetry Metal Oxide Semiconductor (COS-MOS).

The battery keeps the clock on modern PCs

Modern PCs often no longer use CMOS RAM, but rather the BIOS settings in non-volatile memory, which means that the settings do not need constant power to be maintained. So if many PCs now store BIOS settings in non-volatile memory that doesn't need a battery, why do motherboards still come with batteries? Simple: Motherboards still include a Real Time Clock (RTC). This watch works all the time, whether the computer is on or not. The real-time watch is essentially a quartz watch, just like the ones we wear on our wrists. When the PC is turned off, the battery provides power to run the clock in real time. This is how your PC always knows the correct time when you turn it on.

As we all know from experience, batteries don't last forever. Eventually, a CMOS stack will stop working. This can happen between two and ten years from the date the motherboard was manufactured. If your PC is on all the time, its battery will last much longer. If it's turned off most of the time, your battery will run down sooner, after all, you're using the battery more.

Problems when the battery fails

If the battery fails on an old PC that stores its BIOS settings in CMOS, you will see error messages like "CMOS Battery Failure", "CMOS Read Error" or "CMOS Checksum Error" when you start the team. You may also see more cryptic error messages, such as "New CPU installed", this makes the motherboard unable to remember that the CPU was previously installed, so you think it is new every time it starts. On a newer PC that stores its BIOS settings in non-volatile memory, the computer may boot normally, but may stop keeping track of the time when it shuts down.

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This ends our article on motherboard battery: what is the battery and what is its function. You can leave a comment if you have any questions or want to make a suggestion.

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