What are CMOS or clock backup?

Posted on April 5, 2010, 7:49 pm

Batteries and battery backup CMOS Clock perform the same function in desktop and laptop computers: when the computer is off, the battery keeps the time and date, ensure their accuracy when the system is restarted again. More importantly, saves the CMOS battery from the computer, set-up configuration, which allows the system to restart effectively once it is restarted. The computer knows what type of disk drive in its care, etc. Not surprisingly, these batteries are known alternatively as CMOS batteries, the real time clock (RTC) batteries, or simply internal batteries. Dell Inspiron 1525 batterieLes chemistries most common CMOS battery are lithium, nickel-cadmium (NiCd) and alkaline. They are usually somewhere in the 3 to 7. 2 volt range and either solder onto the motherboard or simply plug in via a snap connector (depending on the design of the computer manufacturer). In most cases, replacing the CMOS battery is an easy task . It is simply a matter of locating the battery on the motherboard of the computer, remove and plug in again. Typically, the batteries should be replaced by the same type of battery that was originally used in the machine, or according to manufacturer’s specifications. The main exception to this rule are older IBM compatible computers, which come with a NiCad battery soldered onto the motherboard. These computers generally have three or four pin male plug with two pins connected via a jumper (which is usually found in the same area of the motherboard as the original battery). This plugin allows you to leave the battery soldered in place and replace it with a plug-in type battery. Removing the jumper tells the computer to ignore the battery soldered onto the motherboard and look to the pins of its power source. IMPORTANT NOTE: The batteries are rechargeable Ni-Cad, while alkaline batteries and lithium batteries are not. Therefore, lithium and alkaline batteries must be replaced by equivalent batteries of the same type. The attempt to replace these non-rechargeable batteries with a NiCad will result in a stack not functioning due to the fact that the computer lacks the proper charging circuitry. If a motherboard lacks the provision discussed above for an external battery, the NiCad battery MUST be soldered and replaced by a NiCad battery ONLY. Trying to use an alkaline or lithium batteries instead of NiCad on such a board can be hazardous. These batteries are not designed to be recharged, and an attempt to do so may cause the battery to “burst” or exploser.CMOS batteries usually last two to three years, although some (including the lithium type) have been known to last much longer. Ironically, the less you use your computer, the faster the CMOS battery will run out. This is because when your computer is turned off the battery begins to function. It is recommended to replace the CMOS battery approximately once per year, or when servicing the computer. If your computer has been idle for an extended period, it is a good idea to change the battery. Change the battery is relatively easy and inexpensive, especially (as I am sure many of you know) compared to trying to reconfigure a computer which has lost its settings CMOS.rescouces: http://www . laptopbatteryretail. co. uk/sony-vgp-bps8-battery. html