Who knew Thinkpad batteries require a jump start?

Lithium battery packs reaching the end of their life usually have a lot of kick left in them. That’s because they’re made up of multiple cells and it only takes the failure of one to bork the entire battery. One of the most interesting examples we’ve heard of this is in the Toyota Prius, but that’s a story for another time. In this case, [Mika] wanted to resurrect the battery from his IBM Thinkpad T40. He identified the offending cell and replaced it, but couldn’t get any juice out of the battery after the repair.

He was measuring 0V on the output, but could measure the cells instead of the control circuitry and was getting over 11V. Clearly, the control circuit wasn’t allowing an output. We completely understand the concept here (think about that really bad press about exploding laptop batteries). It seems there’s a lockout mechanism when the control circuit loses power. [Mika] managed to get past this by shorting voltage into the control circuit, a method he likes in the video after the break to jump starting a car.

We’ve seen similar cell replacement for power tools, like a Dremel or a Makita drill.

54 thoughts on “Who knew Thinkpad batteries require a jump start?

  1. This is interesting, I know that protected 18650 and RCR123A cells have a small built-in IC that sits under one of the terminals and cuts the connection between the cell and the terminal when the cell voltage drops below 2.8V or 3V. The protection IC then needs a “jump” in order to get it to re-establish the connection for charging, this usually involves applying a high voltage (around 5V is enough) to the cell. Some 18650 chargers have an open-terminal voltage of 5V to kick-start any protection circuits that have locked out.

    I suppose laptop batteries have similar circuits.

  2. I’ve resurrected old laptop batteries like that as well. When I traced out the circuit inside the battery (with extensive Datasheet googling) what I found was that the control circuit was powered by the battery side even when the battery was connected to a charger. This turned it into a brick after it discharged far enough that the control circuit regulator dropped out.

    To bring it back to life I just trickle charged the battery pack directly (bench supply plus a fairly high value resistor like 100R) until the pack voltage was high enough to power the charging circuitry. After that it could go back into the laptop and charge normally.

    Unfortunately there are parameters you can set in the pack’s chips which are lost when they power off (no flash storage) so the battery pack was not quite “right” after that.

    1. I agree man, I just recently upgraded my laptop to an Asus gaming notebook and I gave my Mom my T60. The problem is the battery friggin died due to her overuse of an already old battery. (So it remains tethered without the battery missing b/c you can’t keep a dead battery in a Thinkpad as it won’t run.)

      Needless to say it looks goofy without the battery in the back. I found a replacement for 10.00 though through Google shopping so I doubt I’ll goto the trouble to replace the cells.

    1. I am also interested in the comment about the Prius. I have not read any thing about that. Since I own one I like to keep tabs on the eventual efforts I may need to make to keep it running.

  3. probably stupid information that is already known
    but dont forget that laptop batteries have a “on” pin as well that needs shorting to ground before they will supply voltage, i recently modified a laptop battery to power some speakers(and i ended up killing after charging it wrong using a 12 volt supply
    was from a similar thinkpad

  4. Interesting had some similar problems, i’ve bought a cheap replacement battery for my “aspire one 150A” when I switch the battery to the replacement, I cannot boot, I have to plug the notebook for about half a second to a charger before i can use the replacement….

  5. Had a similar thing w/ lithium polymer battery on a Kindle DX. Friend gave it to me because it wouldn’t charge any more and thought it was toast.

    Ended up the cell voltage had gotten too low on the pack and the charge controller wouldn’t charge. Opened it up and force charged the pack with a lab power supply and it has worked great ever since.

    1. Did the same thing with an ipod touch 2g. The thing was given to me totally dead, but after charging it slowly from its original voltage (2.0ish) to 3.5, it woke up and began to charge via usb. After getting below 2.5v, it should have lost most of its capacity permanently, but ironically, it is in better shape than my other ipod touch that never had that problem.

  6. Oh, please be careful doing anything like this. If any cell has dropped below 2.8v it is considered damaged and should be disposed of. He should be getting 18volts out of that pack in a discharged condition. If he is getting 11v the entire pack is probably toast and charging it could result in a fire. Thats WHY the circuit is there.

    1. No.

      The pack is configured as 3s2p, 3 cells in series * 2 cells in parallel. Discharged voltage is ~9v, and I’ve seen no reason to think that a pack that is down to 2v/cell needs to be junked, provided the drop from ~2.8 down to 2 happened through gradual self discharge. The thing is, you can’t really trust the series voltage on an pack that’s been sitting around a long time. I’ve had old dell packs that were near 2v in series where some of the cells had reversed polarity, and other cells that were just fine and above 3v.

  7. nice! after reading this, i tried the same on a “dead” nokia battery: with a bench power supply i recharged the naked battery to 3.8v, but the terminal would still be 0. connecting the *negative* side on the terminal to the negative of the battery fixed it.

  8. People! You _can_ do this (as I have on RC batteries) but it’s not a good idea on anything that you might leave unattended. Lithium batteries are insanely temperamental. These circuits are there for your protection, not because some company is trying to force you to buy ‘their’ brand.

  9. My Sony Ericsson X1 keeps “over-discharing” its battery to about 3.3 volts, and refuses to charge it. Nothing that a 5V supply, a 1 ohm resistor and a ammeter can’t fix… 1.5 A for about 20 to 40 seconds is usally enough to bring the voltage back to a level where the phone will start charging it. I should probably be a little more patient and use a 10 ohme resistor, though…

    1. Your car’s hood is there for safety, so you should never open it? Sure, caution is warranted, but there’s no reason to discard an entire pack for one aged cell. I don’t think I’d go to this sort of trouble to make it work, but props to those who do.

      1. i wouldn’t do it either, but placing some of theese in a transformer box with some circuitry could make a good external baterry, not as nice and powerfull as those factory made ones. but it would be very cheap….in fact free, as you would have thrown them anyway,

  10. I agree with the warnings above.

    Letting a lithium ion battery discharge below a certain voltage causes permanent damage.

    If that battery is then recharged, there is a possibility it may fail in catastrophic manner, catching on fire and/or exploding.

    Manufacturers wisely choose to prevent this possibility with an undervoltage lockout circuit; not only for their own protection against lawsuits, but for their customers’ safety.

    The lockout is typically set to be overly cautious. If you choose to bypass it, most of the time nothing bad will happen. But you are still taking a risk by doing so, and you should be prepared for the worst. Especially since burning lithium ion batteries *cannot* be extinguished by any means! I would at very least recharge/discharge for a few cycles while attended. Look for signs that cells might be swelling. Do it somewhere you can handle an unextinguishable fire.

    1. I was aware of the undervoltage panic state; but not of how to reset it. Thanks for the tip!

      Everyone do be careful, though; Li-ion cells can become very nasty beasties. (See various warnings in others’ comments.) Any battery that you wake up from this state should never be charged unattended, and charging should be done in a fireproof (not merely resistant) environment.

  11. You have no idea how helpfull this article is to me. I have a T61p that i was issues when i went to college, 1.5 years in my battery dies suddenly. I go to my repair place to get information, and walk out with 12 or so “dead” think pad batteries. Now in the end one of the ones i got for free form the garbage worked and i was saved, but i took apart 10 or so think pad batteries and was wondering what was wrong with them. Some had bad cells, but others like mine, just failed overnight. I thought there was a sort of one time fire thermal fuse, as mine had been running a CAD program when i had put it to sleep in a Styrofoam sarcophagus.

    Finlay i get to re-assess the value of my pile of Li-ion cells, i may be able to fix batteries instead of just waiting to design some sort of large battery power supply project.

  12. If you use the on-board charger to replenish the batteries, it will charge them at a low current up to a certain voltage and only then charge them normally.
    You can do this as well with a constant current source. Use something like 100mA and monitor the voltage on the terminals until it reaches say 40% (or 50% if you want to play it safe) of its nominal value, and then you can pump current into them.
    If the voltage refuses to rise even after a few hours they’re probably toast.

  13. I work with single-cell lithium polymer batteries at work. I would imagine that they use the same type of protection mechanism that is used in the larger batteries. The quick trick we use to reset the under-voltage lockout is even easier:
    1) Set a multimeter to check continuity (beep when a short is detected)
    2) Touch the multimeter leads to the + and – terminals of the battery pack
    3) Touch the multimeter leads to the – and + terminals of the battery pack (switch which probe touches which pin)
    4) Use the multimeter to measure the voltage across the battery. It should now be >0V as the protection circuit has been reset.

    And you’re done! This works because the multimeter has to pass a small current through the leads to measure if there is a short-circuit. The protection circuit in these battery packs is designed to lock out the battery and prevent over-discharge until a trickle charge is applied to reset it during a future charge.

    Remember that over discharging lithium battery is will rapidly damage the battery. This trick will restore a battery but the best policy is to design your project so you don’t trigger this protection mechanism.

  14. While it’s easy to change a bad cell, it can be dangerous. A brand new cell has a different discharge curve than an old cell, and it could cause problems. If you change cells in a battery, I’ll suggest to change all of them at the same time.

  15. Get on YouTube and watch videos of batteries exploding. It’s not violent. The battery bubbles slightly and expands, but it doesn’t ESSPLODEZORZ everywhere like many of you are implying.

    If you do modify your battery, test it a few times in a safe place. In other words, don’t use your laptop on your lap the very first time you try to use the new battery. Use it on a table that you don’t mind hurting. Obviously, a phone battery isn’t a big deal, because you never charge it in your pocket.

    1. it actually can ignite and be very dangerous in a standard bedroom or even lab, it’s not a grenade, but the flame it produces IS hot, and WILL burn anything you put near it (just don’t roast marshmallows, it probably will make them all lithium coated)

      also I have seen them burn, and it’s a blue-ish/ purple flame. (Macbook pro battery, even their batteries going up in flames are flashy) it’s not really something I’d want in a carpeted room, or even anywhere inside my house.

  16. I think this may be inherent of lipo over/undercharge protection circuits, the ones I get from batteryspace act the same way; the circuit needs to be kickstarted when newly-connected. The circuit regulates on one pole, the other pole is a direct connection. Bypassing (shorting) the regulated pole fir an instant seems to activate the circuit. I found this out myself and posted it to my supplier’s page in the reviews:


  17. Stolen from the internet, to clear up some common misconceptions about Lithium Batteries, both single use and rechargeable:

    8.3.1 Lithium (Primary, Non-Rechargeable) Batteries
    • Lithium will burn in a normal atmosphere and reacts explosively with water to form hydrogen. The presence of minute amounts of water may ignite the material and the hydrogen gas. Lithium fires can also throw off highly reactive molten lithium metal particles. Cells adjacent to any burning material could overheat causing a violent explosion.
    • Use an extinguishing agent that is best suited to quench the bulk of the fuel that is available. For example, if a single cell were to start burning, a Lith-X Class D extinguisher should be used to quench the fire.
    • If other combustibles catch fire as result of the lithium battery, then use the appropriate extinguishing agent to douse these secondary fires. It is important to address each type of fire with the appropriate extinguishing agent.

    8.3.2 Lithium Ion (Secondary, Rechargeable) Batteries
    • Rechargeable, secondary cells utilize lithium ions that are intercalated into graphite, lithium metal oxides and/or lithium salts. There is no metallic lithium in a lithium ion battery.
    • Because there is no metallic lithium in a lithium ion battery, ordinary extinguishing agents (e.g., ABC extinguisher) can be used effectively on a fire involving lithium ion batteries

  18. I have tried to resurrect my Thinkpad T400 battery. I put in new cells, higher amps (2600 instead of 2200), but no voltage is coming out of the battery pack. The negative pin is fine, but nothing out of the positive side. I tried the trick above but still doesn’t work.

    Is there anything else I can try? I don’t want to waste $53.

    1. Unless you have an I2C adapter and the appropriate software, you now have an expensive brick. Sorry.

      What none of the above posts mention is that the battery controller needs to be programmed. It has volatile memory — if the cells are disconnected, the memory gets erased and the battery *will not work*. There are ways to do a battery rebuild, but they all require special tools and this is exactly why almost nobody is doing this DIY. It simply isn’t worth the additional cost and effort.

      The examples you see posted on the Internet all have at least one of the following characteristics:

      – Either they were done on much older laptops with very simple battery controllers, or
      – The resulting refurb battery fails to work as expected (does not retain a charge, does not give reliable charge time remaining, or does not work at all)

      Expensive, time-consuming, and unreliable. Buy a factory battery.

  19. This explains why the junk aftermarket batteries haven’t worked in my X40. Does anyone know where I can buy a GOOD battery for an X40? Lenovo doesn’t make them anymore.



  20. hi Mike,

    i’ve tried your nice little trick for the battery of my Lenovo T61 but, unfortunately,
    this didn’t work (neither for the positive nor for the negative ends of the cells).

    i guess that the chips on the board of your battery are of different types.
    in order to check this hypothesis, it would be very kind if you could post
    your chip types here.

    on the board of my battery there are 2 TI chips of types BQ8030DBT and

    the Lenovo power management software shows “SANYO” in the manufacture
    field. do you see a different string there ?

    thanx a lot for your help !

    cheers – Herbert

  21. my battery is ok .it is charging well from other lap top . my adapoterchecked ok. but battery is not getting charged by the laptop. connection point of power is checked ok. is there any locking inside the system to prevent charging get me a solution

  22. Thanks to the author of this article. I had the exact problem on ThinkPad T400 battery pack where cells together showing good voltage but the batt. connector showing 0v. And the laptop just showed batt. icon/light blinking orange, Power Manager showing batt. charging for two overnights, Reset Batt Gauge never helped though left for overnights. Pulling apart the batt. pack showed all the batt. cells are showing good same volts of nearly 2-3v. So I followed this article, used a voltmeter as load between Pin 1 & 7 of the batt. pack connector and did a 1-1.5 seconds shorting the +ve of the cells to Pin 1 (+ve), then the voltmeter slowly raised to show the voltage which is equivalent to the voltage shown directly by the cells in series. Thanks for the published article. Appreciate it. And as everyone says, shorting is not a safe one as it may damage the circuitry. So try to make it very very short timed one.

  23. Whats this about an on pin?
    My laptop wont supply power to the battery nor will the battery supply power to the laptop. My son removed the battery for a couple days and it wont charge anymore. before that it was fine. ran the ,machine for almost 90 minutes.

    The voltage on all cells is between 3.4 and 3.9 total voltage just under 12.
    shorting battery pack positive to output pin does not keep it on. (thinkpad Z60m).

    shorting battery pack positive to output whilst on the machine and unplugging the Ac adapter runs the machine.

  24. My sony vaio E series battery was not getting charged while in the laptop. I opened the battery and charged it externally at about 400mA for few minutes. later it resumed charging normally.

  25. Hi, i have a Thinkpad T40, my question is, does this laptop needs the battery to be healthy in order to boot up and function properly? Can this laptop function properly with the battery unplugged and using only the AC adapter? Because my T40 now boots up, display is normal and you can let it stay in the bios for how long you ever want but whenever it starts to boot up after the bios initialization and starting to load windows or linux it suddenly blanks and shuts down. I have already tried disabling all adapters in bios, even removing some wifi and modem inside and also testing exchanging RAM and still got the same problem. I have even removed the hardisk and using only the DVD drive to boot puppy linux and still got the same problem. Can you give me some idea what else should i do or what do you think is the problem with this? Thank you.

  26. I have at least 4 Thinkpads in my family. SL300 and T410 are the newest ones. All of them need a new battery. I wanted to take for each 6x Panasonic NCR18650A with a soldering lug. How can I reset my electronics? Stephen mentioned an I2C adapter and the appropriate software. Where can I find more information about it?
    Greetings Alex

  27. Here is another methodology that you can try without opening the pack. Normally, there is a plastic sticker on one side of the battery that gives the information about the item. Pry open from the edges with a hobby knife. You should be able to see the positive and negative end respectively. The trick lies in determining whether the negative end is terminated on one of the external connector pins. Insert a thin wire through the gap at the negative end. Use a multimeter on continuity mode and check if there is a continuity between the external negative pin and the battery terminal. If there is a continuity, it means it is a positive switching battery. Remove the wire from the negative end and insert it at the positive end and try and make a connection. Test out if the battery shows some voltage by connecting the voltmeter across battery positive terminal and the negative at the connector end. If it shows around 4.5 volts you can still salvage it by directly charging it with a 12V power supply. Keep monitoring the battery for any warming up issues. Once the battery reaches 10.8 volts and stays at that remove the connections and put the battery back in the laptop. Plug in the laptop to the external power and switch on. The battery charging light should come on. Turnoff the laptop allow the battery to get fully charged. You are now good to go. Just remember to cycle the battery regularly. You will fin quite a few articles on the internet about cycling the battery. I have salvaged DELL, HP and Lenovo batteries using this method. You dont have to cut open the batter at all unless you notice some bulging or the above method does not retain charge for long.

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