[SOLVED] How long do ML-1220 CMOS batteries last?

Sep 4, 2022
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I have an Acer Aspire E5-571-7776 laptop. It's about 7.5 years old at this point. I plan to replace the WIFI card and I figured that I might as well try replacing the CMOS battery as a precautionary measure. From my past experiences with opening this laptop up, I know that it has an ML-1220 CMOS battery that's soldered onto the motherboard.

Based on some light research I've done, apparently ML-1220 batteries are rechargeable and for laptops that use them, the motherboard recharges the battery whenever it's powered on. I haven't really found much information beyond this and I figured that ML-1220 batteries apparently aren't very commonly used as CMOS batteries.

I do use my laptop pretty frequently, so I figure that the CMOS battery stays charged pretty frequently. Do I have to worry about the CMOS battery ever running out? What are the chances of failure? How much longer will it last? Since it's a 7.5 year old laptop, should I replace it?

I also do not have any experience with soldering. I do have another old Aspire laptop that uses the same type of battery; I plan to practice on that one before I try replacing the battery on my current laptop.
 

Karadjgne

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Depends on power state. That battery is never used except in full power off, the mains supply recharges it, but the main battery maintains cmos in standard off. It's only when the main battery is disconnected that the cmos battery takes over maintaining voltage to cmos. Same as with a desktop.

So the depletion rate will depend on 2 things. How long and often the main battery is fully depleted/disconnected and how often that happens. You can only recharge batteries so many times, and if the battery is taken to full depletion (good for NiCad, terrible for lithium) it's going to severely affect is recharge/aH state.

Could last 2hrs or 5years, depending on abuse levels.
 
Reactions: CountMike
I keep seeing answers about 4-5 Years and heard that you have to replace them if you do not play on laptop for along time

it provides power even when the computer is off and allows the CMOS to save all the settings [source: Indiana University]. You can expect the CMOS battery to last for up to five years. The more your computer is used, the longer the battery will last.
 

Karadjgne

Titan
Ambassador
Depends on power state. That battery is never used except in full power off, the mains supply recharges it, but the main battery maintains cmos in standard off. It's only when the main battery is disconnected that the cmos battery takes over maintaining voltage to cmos. Same as with a desktop.

So the depletion rate will depend on 2 things. How long and often the main battery is fully depleted/disconnected and how often that happens. You can only recharge batteries so many times, and if the battery is taken to full depletion (good for NiCad, terrible for lithium) it's going to severely affect is recharge/aH state.

Could last 2hrs or 5years, depending on abuse levels.
 
Reactions: CountMike

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