My pc was unused for several months(its a 5 year old acer desktop) and on boot up a screen came up indicating that the CMOS battery was low. Any time I restarted, as expected, the same screen came up and the time and date reset. However, I left the PC on overnight and the battery seems to have magically fixed itself. I know people are saying that the CMOS battery is not rechargeable but it seems that, in this case, that is exactly what has happened. Anyone have any insight to this phenomena? Just curious now.
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The cmos battery is unrechargeable. It is your home electricity supply power to keep your bios data. If you unplug your power cord (like completely disconnect your PC to your house electricity) for a while, you should see bios warning message again.
Hardy
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The CMOS circuit has some capacitance. The current draw is so low that this capacitance can power the memory for some time, possibly hours or even days. The battery is, was, and always will be dead.
David Schwartz
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If your computer was plugged in, the power supply was likely providing power to the RTC/NVRAM (i.e. CMOS). I don't think the CMOS would be corrupted on most hardware if the CR2032 battery was dead unless the system was unplugged and had no other power. Some hardware may be different.
LawrenceC
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CMOS BATTERIES ARE RECHARGEABLE BECAUSE,LAST TIME,SOMEONE BROUGHT HIS COMPUTER FOR SERVICE AND HE SAID IT HAS BEEN LYING THERE FOR almost 8 months now and when i switched it on,it didn't respond.so i cleaned the dust and reassembled the machine,still,it didn't respond and i left it plugged in for about 2 hours and it came to life when i switched it on.so i conclude that,cmos batteries are rechargeable.
