701C replacement batteries

[MooNWalker]

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...

[MooNWalker]

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?

[RealBlackStuff]

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

[MooNWalker]

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.

[hjanzen]

https://www.mupload.nl/img/81gr7xx0fclav.jpg

Cmos battery replacement

[hjanzen]

Cmos battery replacement

Or you may have a look here:

https://thinkpad-forum.de/threads/16163 ... ans+janzen

[Thinkpad4by3]

https://www.mupload.nl/img/81gr7xx0fclav.jpg

Cmos battery replacement

Remove the tags the picture is WAY WAY TOO BIG!!

[hjanzen]

For the standby backup battery I have used a Panasonic VL1220-1VCE

[MooNWalker]

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!

[goldeneagle]

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.

[MooNWalker]

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.

[goldeneagle]

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.

[MooNWalker]

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.

[goldeneagle]

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.

Yes, definitely put in a disclaimer.

Using a spot welder is definitely not rocket science. I worked for a laptop battery rebuilder back in 2007, so I have first hand experience with them. It's a form of welding, but nothing like if I were building a farm trailer or farm equipment (I hire someone else who knows how to weld to do that stuff for me).

Anyways, I haven't had a problem with either NiMH or Li-Ion batteries. In fact, I just rebuilt 3 x TP600 batteries the other day with a 100% success rate. It's probably not the prettiest job, since I'm reusing the nickel strips Panasonic used in the original packs, but they packs all work and run at least 1-1.5 hours.

Technically, you could probably find a youtube video on it.

760 battery packs are a little bit more complicated. If you open one up (with a dremel and a cut off wheel), you'll see what I mean. It uses 12 cells, and unfortunately, they're not cheap, because you need to use CGR17500. 600's are the cheapest, because they use 18650's.

[MooNWalker]

Using a spot welder is definitely not rocket science. I worked for a laptop battery rebuilder back in 2007, so I have first hand experience with them. It's a form of welding, but nothing like if I were building a farm trailer or farm equipment (I hire someone else who knows how to weld to do that stuff for me).

Anyways, I haven't had a problem with either NiMH or Li-Ion batteries. In fact, I just rebuilt 3 x TP600 batteries the other day with a 100% success rate. It's probably not the prettiest job, since I'm reusing the nickel strips Panasonic used in the original packs, but they packs all work and run at least 1-1.5 hours.

Technically, you could probably find a youtube video on it.

760 battery packs are a little bit more complicated. If you open one up (with a dremel and a cut off wheel), you'll see what I mean. It uses 12 cells, and unfortunately, they're not cheap, because you need to use CGR17500. 600's are the cheapest, because they use 18650's.

Thanks for the hints!

I'm currently still working on 750C/755C battery packs, will be starting on the 755CD/CX/760XX battery packs probably some time in January or February. Have you actually worked on those, would you mind if I hit you up later for some advice?

[goldeneagle]

Absolutely, ask any questions you wish.

I personally don't like the rounded corner 755C(x) packs, because 98% of the time, they've leaked. Like REALLY BAD!
NiMH packs for the 760 series seem to be in a lot better shape. Some 755CX, CD, CV and CDV systems have an extra terminal for a Lithium Ion battery. I think it's about 8 bucks cheaper to rebuild, though I've only found one reseller of 17500 batteries. The NiMH packs use Sanyo HR-AUL, which is basically a 4/5A battery.

They're kinda pricey at a little over 4 bucks a cell, but on the intelligent packs, I'd rather do it right and use quality cells. Save the cheap cells for a 355/360 pack.

Oh, and I like using long needle nose pliers to carefully take the nickel strips off the batteries, and then use the same pliers to make the strips as flat as possible. Sometimes it's hard to resuse them, so I'll use new nickel strips and then spot weld the old on top of the new.