Long lasting cr2032 alternative for motherboard

[wraper]

PCB leakage is less than insignificant (unless its surface is heavily contaminated). RTC/CMOS RAM drains a few uA at most. It it say drains 5uA, CR2032 should be good for 5 years.

The leakage of PCBs varies enormously. They are usually very low leakage, but I have seen some super leaky ones, with signals crosstalking all over the board. I assume those were bad batches. In one case I know it was due to moisture trapped between the FR4 and the solder mask on a large batch of boards. More common its dirty boards, especially in humid climates. Don't fall into the "it isn't a condensing atmosphere" trap. If there is any porosity or dust, that non-condensing atmosphere argument doesn't work. Having dealt with quite a lot of ultra low power stuff I say never discount board leakage until you have checked it out thoroughly.

It must be very seriously deflective to make a noticeable difference in this context.

[wraper]

I tested current on 4 (unpowered) motherboards out of curiosity. All had CPU installed except AM4 board.
AMD AM2+ socket 3.8uA and 3.6uA
AMD AM4 1.0uA
Intel LGA 1555 1.6uA

[coppice]

PCB leakage is less than insignificant (unless its surface is heavily contaminated). RTC/CMOS RAM drains a few uA at most. It it say drains 5uA, CR2032 should be good for 5 years.

The leakage of PCBs varies enormously. They are usually very low leakage, but I have seen some super leaky ones, with signals crosstalking all over the board. I assume those were bad batches. In one case I know it was due to moisture trapped between the FR4 and the solder mask on a large batch of boards. More common its dirty boards, especially in humid climates. Don't fall into the "it isn't a condensing atmosphere" trap. If there is any porosity or dust, that non-condensing atmosphere argument doesn't work. Having dealt with quite a lot of ultra low power stuff I say never discount board leakage until you have checked it out thoroughly.

It must be very seriously deflective to make a noticeable difference in this context.

If you work with ultra low power stuff its quite common to get complaints that the battery draw a customer sees is way above what you quote for your device. Then you go in, investigate, and find a variety of ways people manage to leak away 10 times what the chip takes

[ejeffrey]

And usually there's some LED or test LED on a smoke detector, nevermind the buzzer. So yeah I'm sure it won;t last 10yrs if they are used at all.

I don't know shit but they certainly lie 

What? Of course they work.  Smoke detectors take tiny amounts of current to operate.  Even a standard smoke detector will run several years from an alkaline 9V battery.  The 10 year ones have lithium batteries for low self discharge.

The buzzer should go off for at most a few minutes in the lifetime of a smoke detector, it's a negligible load.  Battery powered smoke detectors, if they have an LED, flash it with a very low duty cycle. 

[wraper]

^It was sarcasm, just in case. Of course they normally last as claimed.

[mariush]

You could get a rechargeable 2032 or 2020 cell and slowly charge it from the 3.3v of your computer during operation.

Examples: https://www.digikey.com/short/nqt090w3

ML2020 datasheet says charge at 2.8v - 3.2v (3.1v recommended) at 3mA or lower. So a 1n5817 diode in series with 3.3v will drop around 0.3v and then you could just add a resistor to limit the current to <mA, 1mA would be plenty to top up the cell.

[richnormand]

Had a device (not motherboard) that worked well for about 10 years with its cell backup battery.
Changed it and it lasted about 6 months. OK bad battery, tried again... same thing.
Measured phantom current.... too high.
Used "quick cool" spray while monitoring current.
Culprit: bad electrolytic cap in a circuit across battery.
Changed it to a good quality low leakage one and no issues for the past 8 years.

[Benta]

Dumb question:
are you sure the MB needs a CR2032 cell and not a ML2032 rechargable?
If you're charging a CR2032, it's no wonder that it dies quickly.

[Kjelt]

Dumb question:
are you sure the MB needs a CR2032 cell and not a ML2032 rechargable?
If you're charging a CR2032, it's no wonder that it dies quickly.

Yes very sure, it is an asus strix z270f gaming motherboard it requires a CR2032 Lithium cell battery.

[Halcyon]

If your CR2032 is being drained in 10 months, then there is something wrong with your motherboard.

Agreed. A good quality CR2032 should last for about 10 years in a motherboard.

Absolutely.

[PlainName]

Dumb question:
are you sure the MB needs a CR2032 cell and not a ML2032 rechargable?
If you're charging a CR2032, it's no wonder that it dies quickly.

Yes very sure, it is an asus strix z270f gaming motherboard it requires a CR2032 Lithium cell battery.

I have an Asus Strix Z270e and, like yours, it gets turned off every night (and sometimes daytime too). That is really off - single switch kills all mains to the PC and anything not needing active power when I'm not there. It is now seven years old and there is no problem (touch wood) with the backup battery.

If yours is running out I would think the motherboard is at fault, even if you're using cheap and nasty batteries, since you shouldn't've had to replace the factory battery yet.

[Kjelt]

Dumb question:
are you sure the MB needs a CR2032 cell and not a ML2032 rechargable?
If you're charging a CR2032, it's no wonder that it dies quickly.

Yes very sure, it is an asus strix z270f gaming motherboard it requires a CR2032 Lithium cell battery.

I have an Asus Strix Z270e and, like yours, it gets turned off every night (and sometimes daytime too). That is really off - single switch kills all mains to the PC and anything not needing active power when I'm not there. It is now seven years old and there is no problem (touch wood) with the backup battery.

If yours is running out I would think the motherboard is at fault, even if you're using cheap and nasty batteries, since you shouldn't've had to replace the factory battery yet.

Thanks probably indeed the case as the current consumption looks high.
Anyway placed two AAA cells for now , replacing those every two years will be a piece of cake compared to having to remove the graphics card etc.

Thanks everyone for the advice.