[lostviking]

I have a desktop computer I bought on-line a couple of years ago. For the last six months the CMOS battery lasts about a month. The computer appears to boot but no display on the monitor. Tried a few things, then put in a new CMOS battery. It booted right away. But, a month later it would not boot. Replaced the battery again, it boots up. What is draining the CMOS battery?

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CMOS Battery (from Wiki):

The memory and real-time clock are generally powered by a CR2032 lithium coin cell. These cells last two to ten years, depending on the type of motherboard, ambient temperature and the time that the system is powered down. Higher temperatures and power-down time will shorten cell life. When replacing the cell, the system time and CMOS BIOS settings may revert to default values. This may be avoided by replacing the cell with the power supply master switch on. On modern ATX motherboards, this will supply 5V standby power to the motherboard even if it is apparently "switched off", and keep the CMOS memory energized.

Of course its possible you have had a string of duff batteries Alternatively this may be the first signs of a developing main board fault.

[Neil Jones]

CMOS Battery (from Wiki):

The memory and real-time clock are generally powered by a CR2032 lithium coin cell. These cells last two to ten years, depending on the type of motherboard, ambient temperature and the time that the system is powered down. Higher temperatures and power-down time will shorten cell life. When replacing the cell, the system time and CMOS BIOS settings may revert to default values. This may be avoided by replacing the cell with the power supply master switch on. On modern ATX motherboards, this will supply 5V standby power to the motherboard even if it is apparently "switched off", and keep the CMOS memory energized.

Of course its possible you have had a string of duff batteries Alternatively this may be the first signs of a developing main board fault.