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T42 CMOS Battery Replacement

T40/T41/T42/T43 Series
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Callahan
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T42 CMOS Battery Replacement

#1 Post by Callahan » Tue Dec 18, 2018 5:10 pm

I just replaced the CMOS battery again in my T42. I order two batteries from an eBay seller. They came with no markings on the yellow shrink wrap but it does work. I guess it's a 'generic' battery. It seems they don't last too long, certainly not 5 years or around that.

In another post someone mentioned that I should consider making my own CMOS replacement battery. I did check that idea out over a year ago but I could not find any correct shrink wrap on eBay. I found an assortment of sizes that was very expensive ... it may have been a large quantity.

I never bothered to check it out any further. Now that I had to replace the CMOS battery again, I would like to make my own CMOS battery from now on. I have three ThinkPads so I want a better fresh CMOS battery to put inside.

Can someone point out an eBay seller or someplace that I could get the proper size shrink wrap to make a new CMOS battery. I would not need an awful lot, a small package should work for me as I would not use it for anything else.

Also, I see the heat guns are expensive, as I remember. I had read or seen on TV over ten years ago on a TV home project ... that a person can just use a 'hair dryer' to shrink the plastic. Can someone confirm this?

A last question ... would this be the proper battery to use for the T41 and T42 = CR2032. I found this information in Google and just want to verify the correct battery. Another article mentioned two batteries: CR2025 or CR2032.

I could just use the CR2032. I have bought them before at the store.

Thanks, Callahan

Thinkpad4by3
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Re: T42 CMOS Battery Replacement

#2 Post by Thinkpad4by3 » Tue Dec 18, 2018 7:48 pm

1) 5 years? More like 15.

2) electrical tape will suffice and I believe for the shrink tubing you'd want, minimum of 4ft tubes.
Thinkpad4by3's Law of the Universe.

The efficiency of two screens equally sized with equal numbers if pixels are equal. The time spent by a 4:3 user complaining about 16:9 is proportional to the inefficiency working with a 16:9 display, therefore the amount of useful work extracted is equal.

Callahan
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Location: Huntingdon, PA

Re: T42 CMOS Battery Replacement

#3 Post by Callahan » Wed Dec 19, 2018 9:20 am

Thanks for the reply ... I was thinking the plastic heat wrap would be better protection, in case the battery would start leaking.

I just figured 5 years would be the life of the CMOS battery. Maybe the fresh batteries bought locally where you can see an expiration date well into the future on the package ... would maybe last longer. The batteries I get are unmarked and seem smaller in size but they aren't expensive and include free shipping.

The old saying ... You get what you pay for !

Thanks,

Thinkpad4by3
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Re: T42 CMOS Battery Replacement

#4 Post by Thinkpad4by3 » Wed Dec 19, 2018 1:08 pm

Callahan wrote:
Wed Dec 19, 2018 9:20 am
Thanks for the reply ... I was thinking the plastic heat wrap would be better protection, in case the battery would start leaking.

I just figured 5 years would be the life of the CMOS battery. Maybe the fresh batteries bought locally where you can see an expiration date well into the future on the package ... would maybe last longer. The batteries I get are unmarked and seem smaller in size but they aren't expensive and include free shipping.

The old saying ... You get what you pay for !

Thanks,
I've gotten cheap batteries that last for min. 10 years.

Also CMOS 3V lithium batteries don't leak.

The ones you are thinking of are the old 3.6V NiCD batteries of 1992. Those leak. 3V Lithium button cells do not...or atleast with shorting them or literally puncturing them. Theoretically it could but thats like saying I'm not riding planes because they have a 1/40,000,000 chance of crashing.
Thinkpad4by3's Law of the Universe.

The efficiency of two screens equally sized with equal numbers if pixels are equal. The time spent by a 4:3 user complaining about 16:9 is proportional to the inefficiency working with a 16:9 display, therefore the amount of useful work extracted is equal.

Callahan
Sophomore Member
Posts: 165
Joined: Fri Nov 25, 2016 7:37 am
Location: Huntingdon, PA

Re: T42 CMOS Battery Replacement

#5 Post by Callahan » Thu Dec 20, 2018 12:30 am

That's good to know - CMOS 3V lithium batteries don't leak. I just figured all batteries could possibly leak at some point.

In the last 8 years or so it seems my CMOS batteries don't last as long as you say they should. I take that they are not the best quality but they are usually 'cheap' to order.
...

Thinkpad4by3
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Re: T42 CMOS Battery Replacement

#6 Post by Thinkpad4by3 » Thu Dec 20, 2018 1:20 am

Callahan wrote:
Thu Dec 20, 2018 12:30 am
That's good to know - CMOS 3V lithium batteries don't leak. I just figured all batteries could possibly leak at some point.

In the last 8 years or so it seems my CMOS batteries don't last as long as you say they should. I take that they are not the best quality but they are usually 'cheap' to order.
...
They might be...but that could also be an illusion. Its hard to exactly pinpoint how long a cell will last without marking cells and checking. Also depending on the machine depends on how long it will last(different time chips). Also note that RTC batteries can fluctuate wildly sometimes. On dreaded DS1287 chips, some of them died within a few years, some are still running 25-30 years later(very few but possible).

So 8 years maybe a fluke battery,maybe the quality is decreasing. I don't see a reason why they should be decreasing though. The CR-series batteries have been standardized for 40-50 years now, and all of them are pumped with the same chemicals. So if the same amount of chemicals are thrown into the same casing...theoretically the battery should last just as long. Only speculation here.
Thinkpad4by3's Law of the Universe.

The efficiency of two screens equally sized with equal numbers if pixels are equal. The time spent by a 4:3 user complaining about 16:9 is proportional to the inefficiency working with a 16:9 display, therefore the amount of useful work extracted is equal.

Callahan
Sophomore Member
Posts: 165
Joined: Fri Nov 25, 2016 7:37 am
Location: Huntingdon, PA

Re: T42 CMOS Battery Replacement

#7 Post by Callahan » Thu Dec 20, 2018 2:41 pm

I found this information earlier today from just a few days ago: Re: X6x CMOS battery wiring

Re: X6x CMOS battery wiring
#6 Post by RealBlackStuff » Mon Dec 10, 2018 9:53 am

dandreye wrote: ?
Mon Dec 10, 2018 9:10 am
Will try making my own then.

Get a new CMOS from a nearby pharmacy.
Take the plastic off the old CMOS.
Carefully tear the flat connector-strips from the battery (from the outside toward the middle, using pliers).
Straighten the old strips as best you can.
Put the black/white strip on the new battery's ground and the red strip on the plus side.
Make sure they cannot connect to each other!
Tightly put some electricians tape or scotch tape around it.
You're done.
-----------------------------------

I will go with those instructions. Electrical black tape does seem to get sticky and funny over time ... with a battery maybe lasting 5 to 10 years ... or more, the shrink wrap could seal everything better.

Also today ... I found a supply company in CA that sells 12 inch shrink wrap tubes in different mm sizes for $1.30 t0 $1.45. I will call them after the Holidays and order a few strips to have ready.

Now I will have to wait patiently for another CMOS battery to go 'dead' before I can try all this out. Maybe all the the remaining CMOS batteries in my three ThinkPads will last for 10 years.

Might be a long wait for me to try my new homemade CMOS 'shrink wrapped' battery out.
...

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