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mysterious battery on 755, 770, etc

Older ThinkPads.. from the 600, the 7xx, the iSeries, 300, 500, the Transnote and, of course, the 701
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Jefferson
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Posts: 62
Joined: Fri Dec 03, 2010 6:05 pm
Location: Denver, CO

mysterious battery on 755, 770, etc

#1 Post by Jefferson » Wed Sep 18, 2019 8:48 pm

please take a look at the pic as it's worth 1000 words :)
(lower left corner, what appears to be 3 CMOS battery wrapped in tandem)

https://cafe.naver.com/tpholictalk/30629


Does anyone know what this battery does?

I'm mainly wordering

- what does it do?
- does the laptop function normally without it?
- does it leak and ruin the motherboard?

thanks!
:banana:
With the original box and documentation : 600, 380XD, 385XD, X24, X30(10th Anniv), T42p, T43, R52, W700ds
Without : 385XD, 600X, 770X, W701, T420, T430, T520, X230
Not working & for parts : At least a dozen
Other laptops : Dell, Alienware, Lenovo
:banana:

Thinkpad4by3
Senior ThinkPadder
Senior ThinkPadder
Posts: 2623
Joined: Sun Aug 09, 2015 9:25 am
Location: N. Bellmore, ny

Re: mysterious battery on 755, 770, etc

#2 Post by Thinkpad4by3 » Wed Sep 18, 2019 8:59 pm

Jefferson wrote:
Wed Sep 18, 2019 8:48 pm
please take a look at the pic as it's worth 1000 words :)
(lower left corner, what appears to be 3 CMOS battery wrapped in tandem)

https://cafe.naver.com/tpholictalk/30629


Does anyone know what this battery does?

I'm mainly wordering

- what does it do?
- does the laptop function normally without it?
- does it leak and ruin the motherboard?

thanks!
1) its a CMOS battery and I also believe a RAM-back battery(ie you put the machine to sleep and swap the main battery and this will keep it alive for a few minutes).
2) gives a 161/163 error on boot but otherwise yes,
3) Yes, but those *RARELY* leak in what Ive found. You should be much more concerned with the main battery leaking.

It is made up of 3 1.2v NiCD cells, basically a flat version of other NiCDs found in machines of a similar age.

Image
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.

Jefferson
Freshman Member
Posts: 62
Joined: Fri Dec 03, 2010 6:05 pm
Location: Denver, CO

Re: mysterious battery on 755, 770, etc

#3 Post by Jefferson » Wed Sep 18, 2019 9:15 pm

Thinkpad4by3 wrote:
Wed Sep 18, 2019 8:59 pm

1) its a CMOS battery and I also believe a RAM-back battery(ie you put the machine to sleep and swap the main battery and this will keep it alive for a few minutes).
2) gives a 161/163 error on boot but otherwise yes,
3) Yes, but those *RARELY* leak in what Ive found. You should be much more concerned with the main battery leaking.

It is made up of 3 1.2v NiCD cells, basically a flat version of other NiCDs found in machines of a similar age.

Image
Thanks. The pic was for 755c but I also seem to recall a similar battery in 770 as well. As you know, 770 already has regular CMOS battery right next to the ram slot.

Does that mean 770 has a redundant CMOS battery system? After so many years, I can't imagine the NiCD battery still functioning at the designed capacity...

Thanks!
:banana:
With the original box and documentation : 600, 380XD, 385XD, X24, X30(10th Anniv), T42p, T43, R52, W700ds
Without : 385XD, 600X, 770X, W701, T420, T430, T520, X230
Not working & for parts : At least a dozen
Other laptops : Dell, Alienware, Lenovo
:banana:

Thinkpad4by3
Senior ThinkPadder
Senior ThinkPadder
Posts: 2623
Joined: Sun Aug 09, 2015 9:25 am
Location: N. Bellmore, ny

Re: mysterious battery on 755, 770, etc

#4 Post by Thinkpad4by3 » Wed Sep 18, 2019 10:02 pm

Jefferson wrote:
Wed Sep 18, 2019 9:15 pm

Thanks. The pic was for 755c but I also seem to recall a similar battery in 770 as well. As you know, 770 already has regular CMOS battery right next to the ram slot.

Does that mean 770 has a redundant CMOS battery system? After so many years, I can't imagine the NiCD battery still functioning at the designed capacity...

Thanks!
Same thing, its a standby battery just it isn't doing double duty with the CMOS settings. Thats handled by the other coin cell like the 701C.
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.

goldeneagle
Sophomore Member
Posts: 142
Joined: Sat May 31, 2014 8:06 pm
Location: Bandera, TX

Re: mysterious battery on 755, 770, etc

#5 Post by goldeneagle » Fri Nov 01, 2019 5:00 am

The NiCAD battery y'all are describing is the standby battery. It ONLY handles keeping the memory state intact when you suspend so you can swap main batteries. It has NOTHING to do with 161/163/CMOS. That's handled by the VL2020. Yes, it is rechargeable. No, you cannot use a CR2025/2032 (unless you theoretically put in a diode, so it wouldn't charge up). Replacement VL2020's are around $15. Not cheap, but they can last 5-15 years.
Historic ThinkPads owned:
300 (x3), more 355's than I know what to do with, 360C/CSE/CE/P, 510CS, 560/E, 600E, 701C/CS, 730TE, 750/C, 755C(x3)/CE(x3)/CX/CDV/CD, 760ED, 770
Newer ThinkPads owned:
T520, W520 (x2), X220 Tablet (x4), and some T61/X61T laying around somewhere

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