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701C replacement batteries

Older ThinkPads.. from the 600, the 7xx, the iSeries, 300, 500, the Transnote and, of course, the 701
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MooNWalker
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701C replacement batteries

#1 Post by MooNWalker » Sun Jan 06, 2019 1:08 am

Yes, plural - this machine has three of them: the main NiMH battery, the standby backup battery (Varta V30H NiMH cell), and the CMOS battery (so far haven't been able to identify).

In the unit I'm trying to restore the main battery leaked, the standby backup battery is suspected to have been damaged (may have leaked itself, though it also could be dried electrolite from main battery leak), CMOS battery is dead. I do have an original main battery replacement, so that is not a concern. My concern is first and foremost CMOS battery, and then the standby backup battery.

I'm still waiting for the soldering iron to arrive to be able to desolder the CMOS battery from the motherboard (it's soldered on the lower side of the bottom planar next to the IDE connector and the RAM slot) and hopefully identify it, but I'd appreciate any info on what is it, what are its specs, and what it can be replaced with. This thread seems to make a claim that a cell used in more modern ThinkPads (apparently a CR2025 type Lithium cell) will be safe to use in 701C, how certain is that? IIRC CR20xx type Lithium cells aren't really rechargeable (are they?), so the main concern would be to make sure that a) the voltage is correct (should be exactly the same across the same type/chemistry) and b) it can output the current it needs to output and still last long enough (hopefully at least few years before I have to re-solder it again). Is my thinking correct?

I already know what kind of battery is the standby backup one, but I can't find the exact replacement. This one is obviously rechargeable, how important is it to match capacity, is it OK for replacement to be of higher? Are there any other parameters I should worry about besides matching chemistry and perhaps current/capacity? What about internal resistance?

It's been a veeeeery long time since I've done anything related to electrical engineering...
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MooNWalker
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Re: 701C replacement batteries

#2 Post by MooNWalker » Sun Jan 06, 2019 1:58 am

I get it that many modern CR button/coin cells (CR - IEC code for cell based on Lithium chemistry) can last many years... But I wonder if an ML1220 cell would be a better fit for the CMOS battery in 701C?
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RealBlackStuff
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Re: 701C replacement batteries

#3 Post by RealBlackStuff » Sun Jan 06, 2019 8:42 am

No, won't work, there's no 'power' going into the battery to recharge it.

On the 701c I worked on, the CMOS was not soldered, but had a socket.
CMOS see here: viewtopic.php?p=828410#p828410
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MooNWalker
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Re: 701C replacement batteries

#4 Post by MooNWalker » Sun Jan 06, 2019 1:31 pm

RealBlackStuff wrote:
Sun Jan 06, 2019 8:42 am
No, won't work, there's no 'power' going into the battery to recharge it.

On the 701c I worked on, the CMOS was not soldered, but had a socket.
CMOS see here: viewtopic.php?p=828410#p828410
I think you're right - I haven't yet been able to remove the solder tabs from the original CMOS cell, but from what I can make out behind them it's a BR1225, which is not a rechargeable type, so it's probably indeed safe to just replace it with something like CR2025/CR2032 used in more modern ThinkPads, though I can't find one with matching solder tabs.

For the standby backup battery I think I found a replacement. It's not an exact model, Varta V30H, as those appear to have been discontinued, but Varta V40H appears to be intended as a replacement for V30H, so I should be able to use that one - just put the existing wires onto new cell's solder tabs, matching the polarity, and then put some heat shrink tubing around it to prevent shorts.
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hjanzen
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Re: 701C replacement batteries

#5 Post by hjanzen » Fri Jan 11, 2019 12:56 pm

600X PIII 650MHz 576MB, 701C DX4 75MHz 40MB, T61

hjanzen
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Re: 701C replacement batteries

#6 Post by hjanzen » Fri Jan 11, 2019 1:04 pm

Cmos battery replacement

Or you may have a look here:

https://thinkpad-forum.de/threads/16163 ... ans+janzen
600X PIII 650MHz 576MB, 701C DX4 75MHz 40MB, T61

Thinkpad4by3
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Re: 701C replacement batteries

#7 Post by Thinkpad4by3 » Fri Jan 11, 2019 1:18 pm

hjanzen wrote:
Fri Jan 11, 2019 12:56 pm
https://www.mupload.nl/img/81gr7xx0fclav.jpg

Cmos battery replacement
Remove the tags the picture is WAY WAY TOO BIG!!
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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.

hjanzen
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Re: 701C replacement batteries

#8 Post by hjanzen » Fri Jan 11, 2019 2:02 pm

For the standby backup battery I have used a Panasonic VL1220-1VCE
600X PIII 650MHz 576MB, 701C DX4 75MHz 40MB, T61

MooNWalker
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Re: 701C replacement batteries

#9 Post by MooNWalker » Mon Jan 14, 2019 8:40 pm

I ended up using CR2032 cell for CMOS battery. Was a bit tricky to fit it next to the speaker, but works beautifully now otherwise. For the standby battery I found Varta V40H with solder tabs.

Thanks everyone!
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goldeneagle
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Re: 701C replacement batteries

#10 Post by goldeneagle » Tue Jul 23, 2019 11:12 am

Did you rebuild your primary battery? I regret tossing my leaked NiMH batteries over a decade ago, as I still have a 701C and CS, though both are stored away.
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

MooNWalker
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Re: 701C replacement batteries

#11 Post by MooNWalker » Wed Jul 24, 2019 1:50 am

goldeneagle wrote:
Tue Jul 23, 2019 11:12 am
Did you rebuild your primary battery? I regret tossing my leaked NiMH batteries over a decade ago, as I still have a 701C and CS, though both are stored away.
Yes. I used 20 AWG wire to solder standard AA NiMH Eneloop cells together. Macgyvered a stand for said cells to hold them in place during soldering - just hotglued few layers of corrugated cardboard together with the hole the diameter of a cell. If you solder it fast enough the cells barely get heated. Need a powerful enough soldering iron for that, and it's best to do it in several separate rounds, giving ample time for the cells to cool off in-between. As in, first put the solder on one cell contact for all cells, then on the other for all cells, then actually attach the wires to one end, then to the other putting it all together in one circuit.

The resulting battery holds charge pretty well, I get about two hours+ of battery life, but it doesn't charge well when the OS is fully booted and it doesn't report the charge correctly because the battery controller was too badly corroded and is non-functional. When putting the battery case together I had to glue the halfs together and then polish it off with fine grained sand paper.
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goldeneagle
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Re: 701C replacement batteries

#12 Post by goldeneagle » Thu Jul 25, 2019 9:02 am

MooNWalker wrote:
Wed Jul 24, 2019 1:50 am
goldeneagle wrote:
Tue Jul 23, 2019 11:12 am
Did you rebuild your primary battery? I regret tossing my leaked NiMH batteries over a decade ago, as I still have a 701C and CS, though both are stored away.
Yes. I used 20 AWG wire to solder standard AA NiMH Eneloop cells together. Macgyvered a stand for said cells to hold them in place during soldering - just hotglued few layers of corrugated cardboard together with the hole the diameter of a cell. If you solder it fast enough the cells barely get heated. Need a powerful enough soldering iron for that, and it's best to do it in several separate rounds, giving ample time for the cells to cool off in-between. As in, first put the solder on one cell contact for all cells, then on the other for all cells, then actually attach the wires to one end, then to the other putting it all together in one circuit.

The resulting battery holds charge pretty well, I get about two hours+ of battery life, but it doesn't charge well when the OS is fully booted and it doesn't report the charge correctly because the battery controller was too badly corroded and is non-functional. When putting the battery case together I had to glue the halfs together and then polish it off with fine grained sand paper.
I'm kinda cringing, because you really should have used a spot welder, though both battery ends need to be flat. I guess it at least works, but I'd still be leery of your method. Though I have noticed some of the battery circuitry is spotty; I built a 760 LiIon battery, and mysteriously, 4 of my cells ended up totally dead. So I'll probably get 4 more cells and just use a new circuit board, and see if it gets any better.
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

MooNWalker
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Posts: 50
Joined: Sat Mar 22, 2008 6:54 am
Location: Seattle, WA

Re: 701C replacement batteries

#13 Post by MooNWalker » Thu Jul 25, 2019 2:41 pm

goldeneagle wrote:
Thu Jul 25, 2019 9:02 am
I'm kinda cringing, because you really should have used a spot welder, though both battery ends need to be flat. I guess it at least works, but I'd still be leery of your method. Though I have noticed some of the battery circuitry is spotty; I built a 760 LiIon battery, and mysteriously, 4 of my cells ended up totally dead. So I'll probably get 4 more cells and just use a new circuit board, and see if it gets any better.
It's not my method, I borrowed it from other people that have successfully rebuilt their batteries. I know, spot welding is how it's done properly, but I neither have any welding training, nor have a welder, nor a one that's not total junk is reasonably cheap. Plus this are AA NiMH cells and not much more vulnerable due to size coin cells or much more dangerous due to chemistry Li-ion cells, and I am reasonably proficient with soldering iron to do it very quickly, without heating unnecessarily. Wouldn't recommend it to everyone (I guess should've put the disclosure in the previous post - don't do this at home kids!), but it worked well enough for me. If I can't find Li-ion replacements for 760 and later though I may end up investing in a spot welder and appropriate training.
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