A typical symptom of a cmos battery failure is a constant boot-up/shutdown cycle on the computer. This cycle will repetitively happen until the system doesn’t turn on one more time. Often there are intermittent visual flickers and/or lines in the event viewer which show that there was an error before turning off, but usually this won’t happen over and over again – it will be just one long error message with no other symptoms. If you are not sure how to fix your problem, please contact support for help from an expert technician or refer to your computer manual which should have been included with your purchase.
A low battery condition can also cause other symptoms such as a power failure during system startup. Certain system boards (particularly laptops) will also show the message “CMOS Checksum Error” or “CMOS Battery Low” when the battery is replaced. Some systems may need to be reset or have their CMOS ‘battery backed RAM’ replaced if this occurs. This is the same type of error that will occur if you change your CMOS battery for a new one prematurely. Any time you pull the CMOS battery out, it must be left out for at least three hours before putting it back in since doing so immediately resets all values to their defaults.
If your system has a non-replaceable battery, it can often be reset by removing the battery from your computer and leaving it uninstalled for at least three hours. This returns all settings to default and will fix things like BIOS passwords that have been forgotten. After at least three hours, reinstall the battery and allow the system to boot. If you are going to leave the old battery out, you should remove it from the computer case to prevent any possibility of a short circuit or electrical shock while working on your computer. (You may be able to find a spot to place the old battery and give yourself a little extra room.) This type of failure doesn’t usually cause any physical damage but if you are still worried about it, remove the power cable and take your computer case apart in case you accidentally shorted something out.
The number one cause of this problem is due to misuse of battery-powered devices such as laptops. The only way the battery can fail is if it becomes completely drained, which is practically impossible for a modern laptop with rechargeable batteries. When the battery does die, it won’t be replaced by the computer’s manufacturer but will have to be ordered (and sometimes soldered in) by a third party repair shop instead. This is the case even if the laptop is still under warranty since removing a destroyed battery from a device can cause severe damage. Before purchasing any battery replacements or physical replacements, make sure that all available vendors and solutions are listed on the motherboard manufacturer’s website.
Sometimes it is not possible to replace a CMOS battery, so repairing your system may also be necessary. Laptop computers typically use non-replaceable batteries which are usually located in the bottom of the battery bay and hard to reach without removing your entire system from its case. Hard drives and optical disc drive can also use the same battery type as well as any other components that you want to try to fix. If your battery is physically damaged, it may not be possible to replace it since the battery bay will have to be opened up in order for the new part. Make sure that the computer’s warranty is still valid before attempting any repairs yourself, but if it is then you can purchase the necessary parts from an independent site such as ebay or online computer parts reselling sites such as newegg.com.
Repairing a dead battery shouldn’t be attempted on its own since you have nothing to test against and may cause damage.