The Li-Ion battery in my IBM Thinkpad X31 laptop has been getting a bit long in the tooth. Rated at a 4.4 AH capacity new, /proc/acpi/battery/BAT0/info told me that it was only holding 1.8 AH now that it was a few years old. (This is normal for Li-Ion batteries, which degrade over time, even without multiple charge-discharge cycles.)
A brand new IBM (or Lenovo now) battery costs over a hundred dollars, but by shopping around I was able to find a "compatible" battery for as low as $50. It was only rated at 4.4AH, but that is relatively close to the 2nd generation 4.8AH batteries that IBM/Lenovo sell for twice as much. I started to wonder if it might be cheaper to buy OEM li-ion cells and simply replace the cells (keeping the case, and charge/discharge electronics). The first step would be to determine what type of Li-Ion cells I'd need to buy, so I decided to open up my old battery.
As you can see, the standard X31 battery has six cells, in three parallel groups of 2. Cells are nominally 3.6volts, so this adds up to 3 x 3.6 or 10.8 volts. In the photo I have removed the shrink wrapped packaging from one cell to view the markings. Note the relatively complicated PCB along the back side of the cells that handles charging and discharging. If you zoom into the photo, you can see that the controller PCB is connected to each end of every pair of cells (orange and black wires to the far ends, silver metal tab connections to the middle two). This allows the controller to charge each parallel pair of cells at a different rate. The controller PCB is also connected to a thermocouple that is resting between the two middle cells. This gives the controller a temperature reading on the cells during charging and discharging. If the PCB detects that the temperature is too high, it can lower the charging rate, or shut down the power draw (and laptop). Also note the heat fuse (small white block in series with the power line between the two leftmost cells) that is designed to open the circuit if the charge/discharge controller for some reason fails to maintain a safe temperature. All of these safeguards are designed to keep your laptop battery from igniting, and will be very important to maintain in any "re-manufactured" batteries.
I actually determined what type of li-ion cells were used by measuring them and then looking for li-ion cells of a similar size. They are about 2.5" high by 11/16" diameter, or very close to the 64.9mm x 18.3m diameter size of a 18650 style cell that I found on www.batteryspace.com.
My battery is rated at 4.4AH, or 4400mAH. As it has three sets of parallel cells, each set of two cells must have a 4400mAH capacity (because they are in series, you add the voltage, not the amperage), so each cell must have a 2200mAH capacity.
From a mAH per dollar standpoint, batteryspace.com's 2000mAH cells are the best value, but I decided that since the total cost difference was only six dollars, I could afford purchasing the 2200mAH cells. These are slightly lower than the 2400 mAH capacity of the newcells that Ibm/Lenovo now use, and I'll end up with a 4.4AH battery (just like the original part number, before IBM/Lenovo upgraded it to 4.8AH).
Just the cells cost $34.20, but I chose to purchase them with solder tabs attached (an extra $1.50) because I figure the people at batteryspace.com are better than me at attaching tabs, plus having extra tabs to work with (those that come on the cells, plus those I salvage from the original cells) will make my life easier. (Besides, the $7 of shipping is the largest extra expense….if the 2600mAH cells weren't almost twice as expensive as the 2200mAH cells I'd have gotten them just get a 5.2AH capacity battery!) The total cost was $43.42. A week later my batteries arrived. (Thanks UPS!)
Important safety note!
You should never replace li-ion cells with cells that have a lower capacity rating, or charge/discharge rate rating. The electronics in laptop batteries are programmed to prevent the cells from overheating and catching fire, and do a very good job as long as the replacement cells in the battery are of equal or higher rating than the original cells.
erdwi,
Unless you have a specialized Li-Ion battery charger, you should be very careful charging them directly (without going through the power protection circuit).
I use a CURRENT controlled power supply, and give them 4 volts at 50 mA (0.05 Amps) until the voltage maxes out (usually a day or so).
Jay
Hi Jay,
My battery only lasted at most 10 minutes so I decided to refill it. I used 2600 mah instead of the previous 2200 mah used. I read that the battery will only charge to 2200 mah. Anyway, the newly refilled batteries are working fine. Only one problem, the battery indicator is wrong. After the first charge for about 2 hours, I turned on windows still charging. It said 3% remaining when really it suppose to be 60% or so. The next day it said 4%. Today it says 6% left. I went through 3 cycles do far. Also when discharging, it said 100% , 99 … to 96 (for about 2 hours) then suddenly dropped to 7% critical battery. Could it be the internal flash chip in the battery needs flashing or something? Or it just needs more cycles?
Thanks
Ok, I tried the command with ubuntu
Here are some lines.
So my battery is already fully charging and does not need cycles?
design capacity: 65486 mAh
last full capacity: 65486 mAh
RM:
I would suggest putting the battery through several more full charge/discharge cycles. (The charge control circuit should eventually figure things out.)
The Linux /proc/acpi information looks promising, perhaps windows battery monitor also needs some quality time with the newly rejuvenated battery to figure things out.
Jay
Will the cycles damage the battery because of the discharging? I read that the life of Li-ion batteries lessen when discharged alot. Any way I will still try it. If none of these work, it has to be some chip in the battery?
So here is a summary from the previous cycle
When charging, charge completes at 6% remaining
When discharging, 100% to 96% is about 2 hours. Drops to 7% suddenly. 7% to dead is 30 minutes approx.
One other thing, when discharging, should I let it discharge until hibernation or take off hibernation and let it discharge all? Hibernation is at 2% so that may not be accurate on the battery timer at this time
RM:
You are right, discharging Li-Ion batteries all the way many times will negatively affect the lifespan of the cells. However, doing in five times (especially if you fully charge it afterwards without leaving it sit discharged for long periods of time) will have only a very small effect on the life of the battery. You’ll have to make a decision for yourself if having an accurate battery gauge is more important than eking out the absolute most life from your battery. (Also, if you never charge your battery to 100%, stopping at 90% each time the battery will last a bit longer.)
Re: Hibernation on low battery – Because the point of the discharge/charge cycles is to fix the battery gauge, it’s a good idea to disable hibernation for this procedure and let the battery go until it is fully dead. (You may find that the battery sits at zero percent for a lot longer than you expect….)
Jay
Hi Jay,
Well, the battery never got better after more than 10 cycles. It never says more than 5% charging when it’s fully charged. I would really like the hibernation to work because it would just cut of when the battery is dead.
Do you know about reseting the battery. I saw a guide about opening it up and connecting a cable to a certain chip. The cable connects to the parallel port of the pc. The pc does the rest to reset the battery. Do you know about this? If yes, can you help me?
RM:
It sounds like your battery is set up to assume that the cells will never be replaced (so it cell life setting only goes down). Re-set information would be specific to your laptop brand and perhaps model, and I am afraid I have no suggestions.
Jay
I rebuilt the battery pack for a Dell Latitude C610 with a 66whr battery (rated 4400mah). The eight replacement cells were Tenergy, Li-ion 18650, rated 2600 mah. The results were disappointing. The old cells had a 50 minute life. The new cells last about 60 minutes even after six charge-discharge cycles. I expected 150 minutes. Secondly the new batteries cost about $70. A new aftermarket Dell battery costs about $105.
Frank:
That performance sounds correct. Your original battery had 8 cells (arranged in four banks of two) for a 14.4v total voltage and 4400mAh total power rating.
Your new battery has 8 cells (again, in 4 banks of 2) for 14.4v total voltage and 5200 mAh total power rating. (Power/current is calculated by the cells in parallel, while voltage is calculated by the cells in serial.)
I would expect your new battery to last 1.18 times longer than the original battery (5200/4400 = 1.18; 50min * 1.18 = 59.00min).
However, if the 50 min life figure was from a “used up” battery, I would expect the new cells to do much better, and if they are not you may be experiencing a problem where the battery control circuit isn’t allowing you to “use” the full amount of power in the cells. Have you tried leaving the laptop on even when the reported power level drops to 0%?
Jay
You are right! With apologies to Shakespeare, the fault dear Brutus is not in the batteries but in the control circuit. By disabling the power management alarms under Windows the batteries can last upwards of 160 minutes. The power level drops steadily to 3% during the first 60 minutes then stays there for another 100 minutes. The alarm’s minimum value is 4%. Bother!
I tried booting Linux which gives more information about the state of the batteries. It reports that the “maximum” charge is about 30% of capacity. The voltage is a more accurate measure of the state of the charge. Apparently it is not used to estimate remaining battery life.
Various internet articles suggest that the control circuit can be re calibrated by letting the power drop to zero before recharging but that hasn’t yet worked for me. If it automagically starts to do so, I’ll let you know. In the mean time I won’t complain too much because I can now spend 2+ hours at the bagel shop before I have to look for an outlet. I just have to keep an eye on the power meter.
Hi Jay,
I tried repacking my toshiba tecra s1 laptop with (some) sucess. I cracked open the battery(opened very nicely) and i removed the old cells and replaced them with ones from a hp battery. I drained the cells, then mounted them exactly the same way as the old ones. One problem…the battery charges rrrrrealy slow (60% in the last 30 hours). Also it doesnt seem to want to run on battery, only works with ac adapter plugged in. Any advice ?
Thanks.
How on earth do you pry open ThinkPad battery cases? Awhile back, someone asked this question, and the suggestion was to use a plastic tool used to open cell phones. But how do you even get the plastic tool to work? I tried a mini flat blade metal screwdriver, but can’t seem to even get it into the seam, what more a plastic tool with a thicker blade. Even if you could somehow get the tool in, and then twisted it to pry the case apart, it seems that the plastic tool would break. Am I missing something?
Azakki:
It’s not easy to pry open the batteries. (I left a few pry marks on the side where I started.) You may need to start off with a very thin blade screwdriver. Once you have it cracked open a little bit, you push the plastic tool inside the crack, and then slide the plastic tool along the crack all the way around. It sometimes helps to have two plastic tools, one right after the other. Twist the one in the back to widen the existing crack, and push the one in the front forward to hold it open. Then move the one in the back farther up and repeat.
Jay
I have the exact problem as frank. The control circuit is not used to the new batteries so they dont report full life. 100% charging for me is 4%. Can letting the laptop cut of when the batteries run dry damage the laptop? It just cuts of when dead. The hibernation is of because of the 4% thing. Also the charging light is on for very long, like at least 5 hours. Can the battery be overcharging?
Thanks
Hi,
I would like to ask two questions please.
I reconstructed an external battery pack for my vaio laptop with 6 Ni-MH cells serially 1.2 x 6 = 7.2 V
each one has 2400 mAh.
I connect this battery poles (+) and (-) separately to the corresponding ones on laptop battery location jack. I know I charge my battery outside notebook with an external charger. My notebook works good but there is no battery meter !
First: what are those poles on the laptop inbewteen (+) and (-) poles ?
they are not connected in my reconstructed circut, is there any hazard ?
Second: can I connect both batteries (my reconstructed one (Ni-MH 7.2V 2400 mAh) and that original one of notebook (lion 7.4 v 2600 mAh)) in parralel manner at the same time ?
Thank you.
M.F. Sherif:
The other connections between the Positive and Negative (ground) terminal are used by your computer to communicate with the charge & control circuit that should be in the battery.
Note that when you take a LiIon battery apart, it typically has a small circuit board that handles the actual charging and discharging of the batteries. This circuit ensures two things:
1) That the battery cells do not get charged “to quickly” and overheat, possibly bursting and releasing Hydrogen gas (and possibly burning or exploding).
2) That your laptop does not discharge the battery too quickly (also resulting in overheating, off-gassing, and possible fire/explosions)
Your laptop MAY draw power from a battery without a charge/control circuit, and it would probably be safe, but I would be very surprised if the laptop would CHARGE the battery before hearing an “everything is OK” signal from the charge/control circuit.
If the laptop DOES provide power to the battery (for charging) and you do not have a charge/control circuit, you risk the battery overheating and burning or exploding.
My major point: Do not use liIon cells without the proper charge/control circuit. The easiest way to get a charge/control circuit is by taking apart a broken battery (although sometimes they are designed to stop working once the battery cells are used up.)
As for your “in parallel” question. The correct way to add more power capacity to your battery is AFTER the charge control circuit. (i.e. put a new cell in parallel with each existing cell to double your capacity).
Note that (newer) charge control circuits manage each cell individually, so putting two cells in parallel where it expects one will work OK, but the two cells will be treated as a single cell, so they should both be of the same “age” when you start. If one cell is old and one cell is new, they will be mismatched and it won’t gain you much.
Jay
Hi !
I have a IBM ThinkPad X31 too and its battery is close to death (30mins of using on batteries).
I’m planning to buy some batteries, but as i found Ultrafire 3000mAh 18650 batteries on ebay, i’m just thinking of about gaining 6Ah of battery instead of 4.4Ah original capacity.
What do you think of it ?
As the cells capacities are superior than the original ones, it would logically not be a problem for the electronic embeded into the pack to charge them fine.
Waiting for your advice to get the right decision.
Simkard,
Original X31 batteries were rated at 4.4AH (using pairs of 2200mAh cells). New X31 batteries are usually rated at 4.8ah (using pairs of 2400 mAh cells). You are correct that 3000mAh cells would theoretically give 6Ah of capacity.
However, this is the first time I’ve seen 3000 mAh 18650 batteries, and since I can only find 3000mAh cells listed on Ebay, you should confirm that they are indeed rated as 3000mAh batteries according to industry standards. (Many cells will do better than their rating at the beginning of their life, but typically cells that are rated as “2400” or “2200” mAh are guaranteed to provide that capacity for a certain number of charge cycles, etc. These 3000 mAh batteries may just be 2600 mAh cells that happen to give 3000 mAh on the first few charge/discharge cycles, but are really no better than 2600 mAh cells. [Or, they could be a brand new cell that is just better than older ones…]
The link you sent advertised them as having “short-circuit and over-current protection”, so they may already contain charge control electronics that you would have to remove before using. I have found 4pc of 18650 @ 2600mAh for $25, so the $35 price seems appropriate.
Jay
My battery is fine. It just won’t charge. Apparently a diode on the motherboard has closed and the AC circut doesn’t work. laptop works fine on battery. just can’t get it to charge. Have you ever made an external battery charger?
Sanford,
I have not built an external charger, let us know if you get one working.
Jay
Hi there, thank you so much for this site. I have a Ibook Rechargeable Battery Model M8403. Please advise if it will be possible to repack this battery and where i can get the cells. I reside in Cape Town , South Africa.
Thank you and God Bless.
Tim
About the battery chip, I have an idea,
will it charge if we don’t actually disconnect the old battery pack until we put new cells.
The idea is to open the case, remove all old batteries together with electronics,
put new cells into the empty case and parallely connect new and old cells, only than when electronics are wired with the new cells disconnect them from the old ones. I’m not much of an expert but theoretically I think they should work?
Bardh:
By doing this (carefully swapping in the new cells) you could keep the charging chip from realizing that the cells had been changed. However, the chip may keep an internal variable that keeps track of how much power is “left” in the cells, and every so often it will decrement the variable, but it is never allowed to increment the variable.
So, depending upon how the programming works, you may or may not be able to get more performance from your “new” battery. Try it out and let us know how it works.
Jay
I’ve replaced the cell of my laptop (IBM ThinkPad R51 2887 MQ6) accourding to your suggestion, Now my laptop is not running on battery ( it runs well on AC power ). in IBM powermanagement software it shows that battery is in good condition but amp-hour is 0.00 , what happened to it?? will you suggest me what should I do now…
Jatin,
Things to check:
1) A wire is not correctly connected and one or more of your cells is not currently connected to the power circuit. Open the battery up again and look for loose connections and make sure all of the solder joins are good.
2) Try the battery in a different laptop. and try the laptop with a different battery to isolate the problem to the battery or laptop. (I’d expect the problem is with the battery, but you never know…)
It is possible that your particular battery has a power circuit that does not allow refills. If you find the solution to your problem, please let us know.
Jay
I’ve check the connections of the battery is looks like all is good …. but now I find out the problem, there is a EEPROM in by battery pack which contains the data for my battery now I need to reset that EEPROM … I’ve Linux script to reset the EEPROM ..I’ll try to reset it this weekends
Regards
Jatin,
Good to know that a software fix exists. Can you post a URL for where to find the script?
Jay
Hi, I just replaced my 4 cells in a Thinkpad X60 Battery. I have a similar problem as Jatin:
– Laptop doesn’t start from battery
– When the power cord is connected, the battery sign blinks orange
– When starting the computer, battery status informs that “irreparable dammage”
It seems that while rebuilding the cell, the chip’s error bit was set. There are programms to reset Eeproms of SMBus based battery packs (AccPlus, SBWorkshop). I was wondering if it’s possible to use an Parallel port to SMBus adapter and reset it with Linux Software.
Does anyone know the pinout and specifications of thinkpad battery connectors?
Thanks for the interesting story. Just curious: why do the cells need to be soldered? Can they be used touching (under spring tension), safely?
Tim,
LiIon cells do not typically have “nubs” at the top like a standard AA battery, so pushing them together will not necessarily make electrical contact. (Plus, laptop battery cases do not have springs.)
If you made sure that each battery had good electrical contact with the next one, and had a spring to hold them under tension, I see now reason you could NOT hold them together with springs, but I suspect that a soldered connection has better electrical properties.
Jay
hello, i got a thinkpad t23, the batteries
are the same, the red ones.
I need of 10,8 Volt and 4.400 mAmpere
please can you tell me the correct URL to watch ? http://www.bateryspace.com and the other part of the URL which is ?
awaiting your reply,
Paolo
Paolo,
You can purchase any of the 18650 batteries. They come in various different capacities and costs, but any 18650 battery will physically fit.
Jay
I haven’t tried it yet but, I think a spark plug gapping tool might help to open up the battery packs a little.
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For those of you who are having probs with your new packs not charging. Most smart chips memory is erased when power is lost and therefore wont charge anymore. Never disconnect power from the chip hook up a secondary source with a 100k ohm resistor and dont remove it until your new pack is hooked up to the chip.
Before removing my old cells, should I make sure they are empty? If I remove them when they are supposed to be fully charged is that a problem?
Also, if I get 2600mAH cells instead of 2400mAH ones like those in my battery, will I get a battery that lasts longer or am I just going to waste money because the laptop will treat them as 2400mAH cells anyway?
Clive:
Li-Ion Cells store best at around 40% charge. If you are just going to throw them out, you could discharge them lower than this, but I don’t see a big point in doing so. Assuming you recycle them in a proper battery disposal location, they will know how to handle them correctly, charged or not.
If you purchase better (higher capacity) cells than you currently have you should get a better (longer) run-time.
Jay
Hello Jay,
First of all, thank you for your quick answer. I was afraid it would take days to get a reply, but a few hours after sending my message I checked your site again and here was your reply. Thank you!
I guess I didn’t explain myself properly about discharging the cells or not before removing them. What I meant is before putting new cells in my battery is it better to have the old ones fully charged so the electronics on the battery will see the cells as 100%? Does is make any difference at all if the old cells were at 100% before being removed? Hopefully, this is clearer this time. 🙂
Clive:
The electronics will have to re-adjust themselves to your new cells over the next several charge/discharge cycles, so where the old cells were shouldn’t matter.
Jay
Thanks for your infos jay !
And sorry for saying: Appearently most of the people here have BY FAR NO idea of how dangerous this “soldering around” is in fact. BR
Wow, almost 2 years and still replying to comments 🙂 Well done. I have recently needed to hack laptop batteries and this site come up in a search. I needed a really long runtime and got it. I was fortunate enough to get hold of some New Old Stock cells for cheap. 20Amp Hours on a IBM T41 goes a long way, unfortunately it does not fit in the original case. I can share a trick to opening up some packs, use a sharp hobby knife/craft knife/boxcutter to cut a wider slot at the seam so you can fit your tool in to start prying.
Hey man,
I just did your little trick on my nearly 4 year old fijitsu siemens pi1536 and it worked perfectly!!
First time it charged in little over an hour, and I then proceded to run battery eater pro v2.70 when it said I had just 20 min over battery time 🙁 But it stuck at 7,4% and it’s still there now after an hour of hardcore processing. So I’m a very happy man!
By the way I had huge difficulty getting the batteries out without destroying the cartrige, which I ended up doing. But I taped somthing up and now I’m home free 🙂
Thanks again!
Greetings for The Netherlands.
Terrific post! I had read this before and just revived my old Averatec battery with cells from my wife’s Dell. It works great!
Interesting point about the gradually increasing capacity. I have started off at 1236mAh and will see if I can work it up all the way to 4400mAh.
PS. You might remember me from GSC at Tech.
Hi Tejas!
It’s not so much increasing capacity, as getting the batteries power electronics to recognize the improved capacity.
Jay
Hi Jay!
Ubuntu refuses to discharge my laptop all the way, so initially the capacity refused to increase. However, I discovered that the laptop’s BIOS has a “battery calibration” feature where it does a full charge-discharge cycle, and bumps up the learned capacity.
I guess this is similar to Surfboy’s situation above (#24), where he ended up using Windows’ Power Meter.
Hi Jay
Good on you for your patience with this many questions answered over so quite a few yrs.
My question:
I’m about to rebuilt my Dell Latitude D620 6 cell pack.
However, here and there I read that I should use “Unprotected” cells for replacement.
I have even seen recommendations to REMOVE the protection circuit from each cell before inserting and connecting them, in case one is using a “Protected” cell as replacement.
The rationale is that the pack’s built-in protector and the cells’ protectors might not like each other and cause conflict.
On the other hand when I look at the OLD cells they clearly seem “Protected” as I can see the notch at one end of each cylinder as well as a stripe along the cells, running underneath the shrinking wrap.
Now could you please shed some light on this issue and get me out of this confusion?
Thanks in advance
Omid,
My laptop had “unprotected” cells, and I replaced them with the same.
If your laptop is using a cell with a built in protection circuit, my advise (with no real knowledge to back it up) would be to replace them with the same thing.
Jay
Jay, I’ve been trying to refills thinkpad T42 batteries, but no luck. I cut the cables from the controller to all the cells, and re-create exact cabling with new cells. After that reconnecting the cells with the controller.
Did I make a mistake here?
Should I keep feeding the controller with some voltage while replacing cells one by one?