motherboard battery question

**irv6744** · March 8th, 2005, 12:06 PM

is a motherboard battery required for the computer to turn on and boot. i thought not but i have not yet experimented. thanks

**Zerotech** · March 8th, 2005, 12:39 PM

A motherboard will boot with a dead battery and tell you that the CMOS information is lost; based on that, I would assume that the motherboard would because no battery would be like a dead battery.

I don't think it would hurt the motherboard if you tried booting tried booting without a CMOS battery.

**Platypus** · March 8th, 2005, 04:37 PM

I would agree with Zerotech's assessment. Depending on how much capacitance there is on the backup circuitry in the board, CMOS memory can hold without a battery for anything from a few minutes, to some hours.

Once this has discharged below the point where valid data will be retained, as Zerotech said, the BIOS will report the invalid state and seek input or revert to defaults, this is basically equivalent to having a flat backup battery. Some BIOS detect the low voltage and report a flat battery.

So a board will normally start up without a battery, but on rare occasions there may be corrupted data still held in the CMOS which can produce an unbootable state. Using the CMOS discharge jumper or leaving the board unpowered for long enough will sort that out.

**Ruslan** · March 8th, 2005, 08:04 PM

Originally Posted by irv6744

is a motherboard battery required for the computer to turn on and boot. i thought not but i have not yet experimented. thanks

From my experience - "No" and ... "Yes!"...

I've seen some motherboards couldn't boot at all with dead battery and I've also seen some motherboards couldn't boot without battery inserted (I still remember one those models - Lucky Star "Phoenix" 5TX1)...
So, now I'm very careful about that - it is always handy to have a multimeter ready on the tech bench... as well as couple dosens good batteries taken from "dead meat"...

**Cyphrr** · March 9th, 2005, 11:43 PM

Originally Posted by Ruslan

From my experience - "No" and ... "Yes!"...

I've seen some motherboards couldn't boot at all with dead battery and I've also seen some motherboards couldn't boot without battery inserted (I still remember one those models - Lucky Star "Phoenix" 5TX1)...
So, now I'm very careful about that - it is always handy to have a multimeter ready on the tech bench... as well as couple dosens good batteries taken from "dead meat"...

I have seen the same thing as well. Most motherboards don't care, but a slight few do. Wierd it-shay