X230 6-cell battery re-celling considerations, 30+ and 44+ battery info [includes pictures]

[greg0rs]

I own two Thinkpad X230, one of them I use daily both at home and at engineering school.
I bought both machines refurbished with working and apparently original lenovo 6-cell batteries. One of the batteries is a 30+ (X220 battery) which works fine in both machines.
I remember reading that the X230 has a battery whitelist and doesn't accept the 30+ battery, so I assume the refurbisher reflashed it.

Edit: the 30+ is not a X220 battery.


Both batteries work well considering their reported age, but the one I'm using regularly is losing capacity (not surprising after 700+ cycles), and I was thinking it would be cool to pop in some new, high-capacity cells and build a 6-cell, ~75Wh pack. I somewhat naively assumed this would be relatively easy to do.

I did some research and found very little information on re-celling thinkpad batteries, and almost none specific to the 44+ battery.
Findings:

• non-destructively opening Thinkpad batteries is hard, the battery may not look too pretty afterwards
• the actual re-celling is tricky on modern Thinkpad batteries because the BMS will blow a fuse if it senses meddling, but it can be done
• re-celling will mess with the charge indicator function
• some (?) 44+ batteries use 4.3 V cells

Today I was trying (without success) to open my 44+. After removing the big label, I saw that there are openings through which the cells are visible.


(top: 44+ battery with label removed, bottom: 30+ battery with label removed)

Observations:

• I can measure the voltage of the rightmost cell pair using these openings
• the cell wrappers match LG ICR18650 C2 cells (printed code on the cells LGABC21865). these are 4.3V cells

What's my grief with 4.3V cells? They have long gone out of fashion and are not available with state-of-the-art capacities.

I quit trying to open the battery and charged it up instead, hoping that maybe the charge controller stops at 4.2V anyway. No such luck, though. The exposed cell contacts measure 4.26V to "ground" on my crappy DMM and the Lenovo Vantage app reports 12.72V (= 3 * 4.24) for the pack.
This means that using modern cells, typically rated for 4.2V+-1% would probably kind of work, with increased capacity even (80Wh pack, yay) but also with decreased safety and very poor cycle life.

After that discovery, I decided to rip the label off the 30+ too.
Observations:

• instead of the small openings, there are big slots here
• the pack internals are different
• I can't easily measure cell voltage
• the plastic under the label is quite thin and flexible, the cells are visible very well, this may be a good entry point into the battery

I charged that battery up too, and it reports 12.5V at 100%. Looks like these are Sanyo 4.2V cells.


I'm now considering recelling the 30+ pack because it seems a lot easier to do, even though it has more capacity left.


Questions

• Has anybody on here tried to recell or successfully recelled a 30+ or 44+ battery?
• Does anybody have pictures of opened batteries or pack internals?
• Do all 44+ batteries use the same cell type?
• How does the connector interface work? If I measure voltage across the slots that say + and -, both batteries measure 12.1V at 100%. This matches neither the reported voltages nor the cell pair voltage that I measured.
• Is it correct that the X230 won't run on unmodified 30+ batteries?

[axur-delmeria]

Another issue is how to reprogram/reset the BMS so that it reflects the capacity of the new cells. To date I've yet to hear of a solution.

[Thinkpad4by3]

What's my grief with 4.3V cells? They have long gone out of fashion and are not available with state-of-the-art capacities.

Nope, they actually have come back into style, as 4.35V batteries and 99% of mobile phones have them...and those do have state of the art capacities.

[greg0rs]

Another issue is how to reprogram/reset the BMS so that it reflects the capacity of the new cells. To date I've yet to hear of a solution.

Thanks for chiming in on this. There is some hope that the BMS can automatically detect the change in capacity after several calibration runs, because it can also automatically detects decreased capacity as a pack ages. On the other hand I have read that many BMSs can only decrease their assumed capacity, not increase.
Do you know how the 30+ / 44+ BMSs behave on this matter, or other Thinkpad BMSs from the era?

If all else fails, a charge indication using the pack voltage should be feasible, but may require extensive software efforts.

What's my grief with 4.3V cells? They have long gone out of fashion and are not available with state-of-the-art capacities.

Nope, they actually have come back into style, as 4.35V batteries and 99% of mobile phones have them...and those do have state of the art capacities.

I have to admit that I'm clueless about smartphones. However, things are quite different in the 18650 world. All recent cells that I know of are 4.2 V.


Further thoughts on 4.3x V 18650 cells concerning pack re-celling:

They [...] are not available with state-of-the-art capacities.

In fact, they are not easily available at all. I am not sure if some are still being manufactured - using old stock cells would go against the intention of making a high-end, high-capacity pack, as Li-Ion cells degrade when stored.
Also, I found the LG 18650 E1 cell. It's a 4.35 V cell with a minimum capacity of 3100mAh that actually comes close to the energy content of today's best 18650s.



Regarding my earlier question:

Do all 44+ batteries use the same cell type?

I have found genuine-looking photos on ebay of a 44+ battery that has a different label than most, claiming a nominal 10.8 V, 5.8 Ah instead of 11.1 V, 5.6 Ah. This indicates different cells, especially since the minimum rating is also different.
It could be 4.2 V cells (indicated by the lower nominal voltage). Or it could be 4.3 V cells that the pack only charges to 4.2 V for cycle life.


I have also made some progress inspecting my battery packs:
I cut the small plastic bridges on the thin, flexible top layer of the 30+ battery (refer to the picture in my previous post) and also cut through the long, wide plastic strip. This allows me to inspect the inside a lot better while still having a working and safe battery with only slightly reduced case stiffness.

I identified the cells in my 30+ battery as Sanyo UR18650ZT.
They also are 4.3 V cells and have pretty much identical specs as the LGs in the 44+, with the same 2700 mAh minimum capacity rating. The actual energy content of the LGs is a couple of percent higher in these tests: Sanyo - LG; but since only two cells each were tested that is of limited significance. Also, the actual lenovo batteries never fully charge the cells, so the effective energy contents will be different anyway.


I was able to directly measure the pack voltage as 12.58 V (BMS reports 12.5 V, 100% charge level). So the 30+ battery presumably (under-)charges its cells to 4.20 V for increased cycle life, meaning re-celling with standard 4.2 V cells will not lead to overcharge. The 44+ battery presumably charges its cells to 4.25 V.
This may explain why my two batteries have different rated capacities despite using cells of identical specifications.
Both my batteries were manufactured in 2013, btw.

[Thinkpad4by3]

Generally, the BMS circuits do not go up in value, only down because they don't want to overcharge the packs. What you could try and find a brand new pack, open it up and record the data from the BMS EEPROM. Then rewrite your old ones with the brand new data and all should be good. Just remember soem TP packs have to be jumpstarted. Look it up on how to do that, because when the battery get cut, the BMS never outputs voltage again so you have to "jump" it by connecting the raw power to the positive pin to fool the BMS into restarting.

Also I experiments with using my 3D printer to make new battery casings but I don't believe they are strong enough, though my printer is compatible with poly carbonate like the original batteries are so I might want to try that one day.

[greg0rs]

One of [my] batteries is a 30+ (X220 battery) which works fine in both machines.
I remember reading that the X230 has a battery whitelist and doesn't accept the 30+ battery, so I assume the refurbisher reflashed it.

[...]

Questions

• Is it correct that the X230 won't run on unmodified 30+ batteries?

Ok, I confused stuff, the 30+ is not the X220 battery at all, the 29+ is.

Where does the 30+ battery even come from? Was the X230i sold with a throttled battery? The 30+ is rated 57Wh, both the 29+ and 44+ are 63Wh.

[vavet]

I had an interesting experience recelling my x61 battery.
It turns out that the BMS from cheap Chinese batteries doesn't care about removal and change of cells. And also it easily adjusts to higher capacity cells.
The bodies of these batteries are much weaker and get fully destroyed when trying to open. So I just used the BMS of a cheap battery in an original lenovo body with some Panasonic high capacity cells (3400mAh If I am not mistaken).

[greg0rs]

Generally, the BMS circuits do not go up in value, only down because they don't want to overcharge the packs.

I doubt that's the true reason. The charging controller and the capacity gauge are different, independent parts of the BMS. The 44+ that I'm testing uses a constant current, constant voltage (CC-CV) charging method, standard for Li-Ion. If a charge limit is set, charging will simply stop earlier, based on the BMS capacity gauge. There is no good reason to assume that any lenovo battery would show different behaviour.
When the BMS is way off on total capacity or state of charge this will obviously result in unpredictable charge levels if a charge limit is set, but the battery can never be overcharged because the fundamental charging algorithm is safe, and will always stop when the cells are at 100% (charge termination is based on cell voltage). A wrong capacity gauge can only ever lead to an earlier stop.

What you could try and find a brand new pack, open it up and record the data from the BMS EEPROM. Then rewrite your old ones with the brand new data and all should be good.

That's a good approach for doing multiple packs, but they would still end up with a lower capacity value than they actually have.
If one were to put in that much effort, it might be feasible to go the extra mile and try to manipulate the data, to put in a higher value.

I had an interesting experience recelling my x61 battery.
It turns out that the BMS from cheap Chinese batteries doesn't care about removal and change of cells. And also it easily adjusts to higher capacity cells.
The bodies of these batteries are much weaker and get fully destroyed when trying to open. So I just used the BMS of a cheap battery in an original lenovo body with some Panasonic high capacity cells (3400mAh If I am not mistaken).

Nice work, thanks for letting me know! Can you set charge thresholds and limits on the knockoff BMS?

[khseal]

There is information on the restoration of the original batteries
http://www.karosium.com/2016/08/hacking-r2j240-lgc.html
http://www.karosium.com/2016/08/hacking ... mware.html

So I just used the BMS of a cheap battery in an original lenovo body with some Panasonic high capacity cells (3400mAh If I am not mistaken).

You need to be careful with the battery voltage. Original batteries often run at 4.35V. I had to change the charge voltage to put the elements 4.2V

I doubt that's the true reason. The charging controller and the capacity gauge are different, independent parts of the BMS. The 44+ that I'm testing uses a constant current, constant voltage (CC-CV) charging method, standard for Li-Ion. If a charge limit is set, charging will simply stop earlier, based on the BMS capacity gauge. There is no good reason to assume that any lenovo battery would show different behaviour.
When the BMS is way off on total capacity or state of charge this will obviously result in unpredictable charge levels if a charge limit is set, but the battery can never be overcharged because the fundamental charging algorithm is safe, and will always stop when the cells are at 100% (charge termination is based on cell voltage). A wrong capacity gauge can only ever lead to an earlier stop.

You are not right. The controllers have at least three charging modes. New controllers are complex and have many parameters.
Some controllers have a 16 bit processor. Some controllers calculate battery capacity by impedance.
http://www.ti.com/lit/wp/slpy002/slpy002.pdf

Has anybody on here tried to recell or successfully recelled a 30+ or 44+ battery?

I successfully restored several batteries.
Capacity increase failed. Batteries with a higher capacity are discharged below 3V. Controllers have a complex capacitance measurement system.
You can restore the battery without flashing. The controller does not block if the elements are properly unsoldered. (Tested LGC Battery)
Battery capacity is less than the factory. Elements of greater capacity were used. Elements 4.2 were used and the charge voltage was reduced.