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Old 03-28-2011, 12:46 AM   #1
Shodan486
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Default CMOS battery life

Just this:

What is the average lifetime of a classic coin battery used in today's computers for maintaining BIOS settings?

And another one : If the battery is placed in the mobo and the mobo is not used for let's say 10, it's surely depleted, right? To be more precise, in what time does the socketed battery dry out while the motherboard has never been turned on?
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Old 03-28-2011, 01:22 AM   #2
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Default Re: CMOS battery life

Not used for 10 what?

Depends on use...
On modern boards the CMOS battery is bypassed any time +5vstb is available.
There is no drain on it during that time.
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Old 03-28-2011, 01:31 AM   #3
Shodan486
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Default Re: CMOS battery life

10 years Sorry for that.

Just wanna know if a board left 10 years of no use, no AC plug, no nothing, has the battery still working...
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Old 03-28-2011, 01:33 AM   #4
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Default Re: CMOS battery life

And no, they are not rechargeable batteries.

I took out an old PII/PIII BX board the other day to test some ECC PC100 RAM.
It probably hasn't been used in 5+ years and the battery was still working.
Of course the cheap Chinese variety probably doesn't last that long.
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Old 03-28-2011, 02:18 AM   #5
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Default Re: CMOS battery life

And is it possible that the battery may show 0.01v on a multimeter after 10 years?
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Old 03-28-2011, 02:33 AM   #6
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Default Re: CMOS battery life

Yes but that's not enough voltage to 'hold up' the CMOS.
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Old 03-28-2011, 02:46 AM   #7
Shodan486
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Default Re: CMOS battery life

Right, that's clear. Just wanna know the numbers...So PCBONEZ, you claim that it depends on the battery manufacturer, rite? Interesting, thought at least batteries, which tend to explode when handled inappropriately, are manufactured with safety provided to the consumers...
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Old 03-28-2011, 03:15 AM   #8
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Default Re: CMOS battery life

the coin cell inside the "dallas module" on my 486DX33 board still has 2.97V
and it's far older than 10years..
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Old 03-28-2011, 02:27 PM   #9
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Default Re: CMOS battery life

I have several Nintendo NES games with coin batteries in them still good after 25 years.
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Old 03-28-2011, 09:03 PM   #10
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Default Re: CMOS battery life

I guess the old saying "your mileage may vary" applies. I replace mine about every 4-5 years or so and on all used motherboards I aquire when I aquire them. Its all trivial since CR2032's and CR2025's can easily be found at most discount retailers for a couple bucks each.
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Old 03-31-2011, 09:52 AM   #11
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Default Re: CMOS battery life

Would it make ANY difference if the OP's ( Shodan486) board had the cmos jumper in the OFF position?

As I understand it, all regular lithium etc cells have a limited lifespan. Thankfully they're not expensive to replace. I'd never throw a board for the lack of one!
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Old 03-31-2011, 07:29 PM   #12
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Default Re: CMOS battery life

Jumper simply shorts the + and - together momentarily [through a resistor so it doesn't fry the battery.]
Leaving the jumper off would have no ill effects.
Leaving it in the reset position for a while would eventually drain the battery.
.
I usually just remove the battery instead of fooling with the jumper.
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Old 04-14-2011, 07:33 AM   #13
cmosbios
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Default Re: CMOS battery life

PCBONEZ, can you please give us an idea of basic BIOS circuit, I mean NOT the circuit inside the BIOS, but the circuit behind the BIOS system on a motherboard. Some kinda diagram and its basic components.
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Old 04-14-2011, 08:00 AM   #14
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Default Re: CMOS battery life

I don't know that one. Never traced one out.
I only know how the BIOS chip is powered.
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Old 04-14-2011, 08:18 AM   #15
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Default Re: CMOS battery life

One thing that interests me, its your profile (About Me page) .. you are interested in chasing women.. and that's the special science LOL
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Old 04-14-2011, 09:07 AM   #16
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Default Re: CMOS battery life

Quote:
Originally Posted by cmosbios View Post
One thing that interests me, its your profile (About Me page) .. you are interested in chasing women.. and that's the special science LOL
Not so much anymore.
The problem is getting away after you catch one.
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Old 04-15-2011, 06:27 PM   #17
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Default Re: CMOS battery life

You definitley can get 10+ years out of them with normal use.
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Old 04-23-2011, 11:46 AM   #18
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Default Re: CMOS battery life

Quote:
Originally Posted by TheLaw View Post

You definitley can get 10+ years out of them with normal use.
Which, woman or batteries? ..............


Dave.
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Old 04-24-2011, 03:25 AM   #19
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Default Re: CMOS battery life

Quote:
Originally Posted by oldnwrinkly View Post
Which, woman or batteries? ..............


Dave.
Depends how hard you use them.....
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Old 04-24-2011, 03:53 AM   #20
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Default Re: CMOS battery life

10 years seems pushing it for a CR2032...

Why worry anyway? Quick test with DMM and if it doesn't work get a new one... If you don't have a DMM use an LED. Works perfect for testing them. It should glow brightly!
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