How To Repair Laptop Batteries

By on February 1, 2017
how to repair laptop batteries










A few days ago I started repairing Laptop Batteries. And in particular the modern Smart Battery Packs. Below my first Pack opened before Repair and Reset. A BQ80201 Controller Board for the Acer Aspire 9411 AWSMi 17 inch Dual Core Laptop. Which didn’t take much time to open.

laptop batteries repair

These packs can’t be fixed by just replacing the 18650 Li-ions by inserting new cells like was still possible with the old Battery Packs (Mostly NiCad and NiMH Packs). Because with the introduction of the Li-ion Battery it is controlled by an intelligent controller Board that keeps track of the Battery temperature, Over voltage when charging, Over current, and prevents Exploding or dangerous Fires . Because Li-ions are very Powerful we need this safety Controller Board as recently was big news when the Samsung Galaxy 7(? I am not familiar with all those new Smart Phones) was cancelled because it caught fire or exploded. And it had cost millions to cancel that Model out of safety concerns. And apparently Li-ion Batteries become very unstable when they get overheated.

I encountered a lot of problems that made it almost impossible for me to repair/fix a Bad Smart Battery at first. I will summarize these points of concern below:

  1. Smart Batteries are read and programmed by using the Philips I2C protocol. Which involves using the 3 wires SDA , SCLK, and GND. And an I2C Adapter Interface.
  2. When we only replace the old Batteries we will notice that when we insert the ‘repaired’ Pack back into the Laptop, it will protest that the Pack is still Bad and it will not charge correctly either. Because the old BAD Pack data is still stored in the Eeprom on the Controller Board.
  3. That’s why we also need to reset/reprogram the previous mentioned Eeprom too. Because the Eeprom on the Controller Board still contained for instance the old Production Date and the Cycle Count of times Charged etc.

Below another peek into the opened Acer Battery Pack (A Sanyo 3UR18650Y-2-QC236 Battery).

fix laptop batteries

Reading the Pack Data and resetting/reprogramming can be easily done with the Full version of the program BE2WORKS. The free demo version only Reads Battery Pack Data. The Full version is not cheap but when we take in account that a single Replacement Battery Pack already easily costs 30 to 60 Dollar/Euro. We earn that investment back after repairing/resetting about 5 Battery Packs.

  1. Because every Battery Pack Connector needs another connector Cable we need to make different versions. Sadly we have to investigate the information of the Connector pins ourself. Like the 7 pins Connector I had to use for my Acer Aspire 9411ASMi Laptop Battery Pack. And my brother’s Acer Aspire 5520G Battery Pack had the same connector but only 10.8V instead of the 11.1V that my Pack had (both Packs about 4400mAh).
  2. I started with the BE2Works demo and therefore had bought the cheap CP2112 USB Adapter to be able to test reading the Battery Eeprom Data. Without that Adapter present the Program will quit. But before reading the Pack by I2C communication is possible we first have to find out the position of the NTC resistor on the Connector. And after I connected that pin to GND the Battery could be read by BE2WORKS. And if the Pack is still in sleep mode we also have to shortly apply an external DC voltage of about 11V onto the Plus and GND connector pins.
  3. Because there was no 7 pin connector Data to be found I started by checking the Plus and GND pins first. And to read out the Eeprom we don’t need to connect the Plus of our Battery Pack to our CP2112 USB Adapter to prevent damage to PC or Adapter. After that I checked with my digital Meter between all pins (except the Plus!!) to Ground if I could measure about 10Kohm that represents the temperature measuring NTC. And connected that pin permanent with GND (on the Connector). And a self made 3 wire connection Cable from the Gnd connection of the CP2112 Adapter was connected to the Battery connector. And the other two wires also from the JP2 connector on the CP2112 represent SDA and SCLK. The CP2112 will be recognized by Windows without having to install any driver.
  4. To prevent blowing up a one-time 4 legged Fuse on the Controller Board that is placed in the Plus Battery Pack connection on the Controller Board, we have to start removing old Batteries by starting removing the Plus wire first, than the lower next Plus, until the last Wire the GND can be removed .

And when connecting new Batteries we for the same reason start in the opposite sequence starting with the Battery GND connection on the internal Controller Board first, going up to the next higher Battery wire, until we finally end with connecting the Plus of the Whole Battery Pack, being the last wire left to connect.

(with 3 x 2 Battery Cells we have to connect 4 wires in total). The 4 legged Fuse (in my case a 12AH3 type Fuse) will get blown if the controller thinks that the Battery is tampered with. Like when the Battery Voltages are connected in the wrong sequence. The Fuse is burned by a controlled FET that heats a resistor inside the Fuse that will immediately open the Fuse. And the Battery Pack Plus is removed from the circuit in the process.  All for safety reasons. 400 of these Fuses only cost about $67 and buying only five of them is also possible. Some say that to prevent this from happening we better at forehand Reset the Controller by connecting that pin to Ground. But if the Protection Flag in the Controller is already Set, the Fuse will probably blow as soon as the Cells are reconnected.

repair laptop batteries

<= The 4 Legged 12AH3 One-time Fuse.

The Battery Connector specs of my 2 now repaired and reset 7 pin connector Packs are as follows:

+ + NTC SCLK SDA – – (gnd)

| | | | | | | <= (7 PIN CONNECTOR)

And as said we do not use the Plus (+) of the Battery Connector other then only for activating the Battery when it is in SLEEP mode as described under point 5.

Before we use and replace the old Li-ions 3.7V (2600mAh) Cells by new ones we have to Spotwelder them with pure Nickel strips onto their contacts. In this case 2 in parallel and that 3 times in Serie. (Parallel doubles the Packs given current). Overheating the Cells by Soldering could make them explode or shorten their life span. (I use a 709A+ Spot Welder for which I had to replace my L16A Weber Fuse automate by a C16A type because the inrush current of the 709A+ was often simply too high).

A Pack with 3 x 2 cells gives about 2 x 2200 mAh, at a voltage of 3 x 3.7 Volt = 11.1 Volt. (In case of my Pack from a Acer Aspire 9411ASMWi 17 inch Laptop).

And in case of my brothers 3 x 2 Cells Pack with another Pack controller, only 10.8V at 4400mAh (Acer Aspire 5520G).

As mentioned before we have to make another I2C Cable to connect to our CP2112 Adapter for any other Battery Pack Connector we encounter. I already ordered the 5 and 9 Pins Male Battery Plugs in case I have to repair/reset those Battery Packs in the near future too. And these are the Chips BE2WORKS can Reset/Reprogram and read: BQ208X, BQ20ZXX, M37512, BQ8030, R2J240, MAX1781, BQ80201, SN8030, BQ20869, BQ30Z55. Below my Brothers old BAD Battery Pack for his Acer Aspire 5520G that costs at least 30 to 60 Dollar/Euro new to replace the old one.

how to fix laptop batteries

And it is good to know that BE2WORKS is able to RESET the PFF (Protection Fuse Flag). But better prevent the above mentioned trigger moments that if they occur set this 12AH3 One-Time Fuse.

laptop batteries spec

As you can see it was still the old BAD Battery Data that is located in the Eeprom. (Cycle count: 223). And it already had lost about 50% of its original Capacity.

After the internal 12AH3 Fuse is blown the BE2WORKS communication with the Battery controller isn’t possible. So we first have to restore that 12A Fuse by placing a short wire over it or by placing a new Fuse. (I used a 0.1 mm thin wire. But I now know how to prevent blowing these Fuses because the Forum and the Site of BE2WORKS were unclear about this subject. And I was told to examine the Controller specs because as they said their program didn’t cover hardware questions. Which didn’t help at all. So now after reading this article any Reader can skip these questions that prevent using the BE2WORKS program the right way!)

be2works adapter

About repairing and replacing old Smart Battery Packs and the price of the Li-ion Cells:

I previously bought 10 of them for about $25/Euro. And those 18650 Cells were all 2600 mAh Capacities (or even more up to 2800 mAh!). The pink/purple Li-ion were original Samsungs according to the Seller!

Which made a big difference quality wise because those 3.7V Cells with names as GTF (9900mAh according to the seller) or Ultrafire (9800 mAh) were a big disappointment. The GTF only gave 963 mAh Capacity, and the Ultrafire cells only 463 mAh !!! To end this article I finally will give some photos of the inside of my brother’s Battery Pack (a Sanyo AS07B31 Pack). Keep in mind that for the same Laptop there are equally useable Battery Packs from different Manufacturers with different Controller Boards but with the same Connector. In case of my Brother’s Battery Pack it took me a lot of time just to find a decent way to open it. It was heavily glued together with double-sided tape, to the Batteries and to the Case. And resetting the BQ 8030 chip took a lot more time compared to my Pack with a BQ 80201 chip. The Eeprom data had to be saved as .bin file (by clicking on the Floppy Disc icon) afterwards. These chips were not sealed, but in case they are BE2WORKS also knows more than 700 Passwords to unseal them. Below the Controller Board with the BQ 8030 DBT chip. And the next Photo shows the position of the 12AH3 4 legged Fuse. Both Photos also show the black wires with the Temperature Sensors that were glued to 2 of the Cells. As can be seen on the Photo after that. And the last Photo shows how in my old Acer Aspire Battery Pack the Wires were connected to the old bad Battery Cells. After opening and removing the Batteries and the Controller Board entirely from the Pack. So If you start by repairing and resetting your old Battery Packs you now know what NOT to do! I hope it was a useful learning experience.

laptop batttery pack circuit board

laptop batteries circuit board

I also bought this complete set of different universal Battery Pack connectors to be used in combination with BE2WORKS which also could be of interest to many readers.

laptop batteries parts

And if I not already told this before, BE2WORKS isn’t capable of reading the Controller Board without internal Batteries connected! Which is the same effect as when the 12AH3 Fuse is blown. And Before anything else ! Be extremely careful with connecting anything to the 18650 Batteries , cause in an unattended moment one of my connection wires short circuited and got up in smoke instantly!

Albert van Bemmelen, Weert , The Netherlands.

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Note: You can read his previous repair article in the below link:



  1. Albert van Bemmelen

    March 16, 2017 at 6:53 pm

    That Spot welder machine looks not bad and has the advantage that
    it only needs 1KW of power. My 709A++ 2 in 1 Spot welder machine
    needs almost twice that amount at 1900 Watt. And in my case I had
    to improve my electric system at home by changing L16 ampère and
    L25 automatic fuses into slower (and higher current providing)
    type fuses. And still now also my mainfuse (which is also only 25A)
    needs to be enhanced too! Which will cost me another extra $200
    dollar/euros extra!
    But my 709A++ has more options, like being able to Spot welder 4
    or 6 upto 8 welder pulses. The more pulses the stronger the
    connection is at the same current. And also the current is much
    higher upto 500 Amps! And it has a solder station with special
    T12 removable heating elements (just replace a defect heater
    element by sticking another one in after pulling the bad one
    And welding pressure also can be regulated, it has a pedal for
    easy foot controlled operation. The Nickel strips can be between
    0.05-0.3mm thick.
    And it also has an extra handy spot welding pen (with also
    2 welding needles in it). Also keep in mind that my Spot
    welder machine costing about 253 euro, came from China why I had
    to pay an extra 28+ euro for importing it to the EU. (My machine
    weighs about 6.9 KG!).

  2. gerald

    March 19, 2017 at 5:21 am

    Hi Albert,
    I can now reset my acer batteries.About spot welding,I've seen this on ebay:
    What do you think about it?I'm afraid with those terms: Electric Leakage Switch Requirement:: 60A or More .
    At home my fuses do not exceed 16 or 32A!

    • Albert van Bemmelen

      March 22, 2017 at 1:38 am

      Fantastic Gerald! I guess you now are able to reset your 4 bad Battery Packs (after of course also replacing the bad 18650 cells)?

      About the 788 you asked. I thought of buying it too myself until I decided that the 709a++ 2 in 1 was a better choice because it also had the hand spot welder tool. And an extra T12 solderstation is more usefull than a charger. Besides every Laptop has its own controlled charger. And else such a charger like the iMax B6 is very affordable too.
      See here:

      So the choice is yours. And maybe also the 788 requires enhanced AC Line Power Fuses.
      (type C16A automatic fuses - Slow type for higher inrush currents - upto at least 63A according to the seller?).

      Nice too hear that you had succeeded fixing your packs, Gerald!
      I only fixed two packs so far. But I'm now trying to fix Makita BL1430 Battery Packs, but I do not know yet what controller they use.

      • Albert van Bemmelen

        March 22, 2017 at 10:03 pm

        What you need to know Gerald is that it is very expensive in The Netherlands to make your Power Cupboard ready for the 63A inrush current of these Spot Welders.
        I just learned that the cheaper 3 x 25A method doesn't apply for me because that would mean that my building society has to replace/convert the complete power installation behind the Main Fuse (now 25A) to a 3 phase installation also (now only 1 phase).
        However the only other and second option of converting the main fuse to 35A is possible but will cost me about 544 Euros!! Still I need to be sure that enhancing to 1 x 35A will be sufficient for the 63A inrush current of my 709A+ device.
        To be safe the rule is to choose the mainfuse at least 2 steps higher than the following fuse. (16A -> 20A -> 25A is 2 steps!) or a difference of about 1.6 x for any following next fuse.

  3. gerald

    March 24, 2017 at 7:22 pm

    Hi Albert,
    It is the reason why I hesitate buying those welders At home my main fuse is max 45A.I have already asked the vendor on ebay for the sunkko788h, the man says I need at least 60A to perform without problems.In my kitchen and bathroom i am protected until 32A (for microwave oven and washing machine).My garage is only 16A fuse protected.I guess I should weld some cells in the kitchen when my wife's at work but that's somehow a bit annoying...

  4. Albert van Bemmelen

    March 26, 2017 at 4:41 pm

    I understand that there are 63A fuses for use at home in other
    But here in my country we can't use or buy them. We also have to ring
    our power delivering company whenever our main fuse is destroyed (on
    paper 35A but in fact now only 25A). That is because that fusebox is
    sealed and we are not allowed to change that fuse ourselfs. It is a
    one-time fuse.

    I can use my 709A++ spot welder machine at home in my garage that is
    fused with a L16A automatic type fuse. But I do not trust doing this
    upstairs at a C16A group that is fused downstairs with a C25A automatic
    fuse, because there are no 2 steps between the C25A fuse and the one-time
    main power fuse. When I use the L16A garage (depository where I store my
    my 2 bicycles and a lot of old scrap electronic parts for repairs) there
    are 2 power fuse steps between the main fuse and the L16 automatic fuse
    (16A -> 20A -> 25A). But still when my main fuse would be destroyed in the proces anyway, they probably wouldn't believe me that I didn't do anything stupid. And have to pay a large bill anyhow. I was thinking of measuring
    the in-rush current with my 400 Amp digital meter. But I'm almost sure it would at least need 63Amps to startup at switch on.
    So if your fuse is L16A (faster type) and resettable and your main fuse
    is 35A it could work.

    • Albert van Bemmelen

      April 3, 2017 at 12:05 am

      By-the-way, Gerald: I regret having bought the 709A+ 2 in 1 spotwelder not only because of the Main Power Inrush problems. Because as it turns out now also the yellow colored square plastic covers on both front welder arms crack/break one after the other.
      And the Seller didn't reply on my complaint that the plastic is just crap material. Its function is probably to keep both arms isolated from each other preventing the upto 800 amps welding both metal arms together. And this also happens because the screw through each plastic cover has to be fastened very thight to keep the copper welding pins in place.
      It is I think therefore not a really well made product and also because of the high inrush problem its asking price is just way too high!


    March 28, 2017 at 12:23 am

    Albert sir i buy this cp2112 adaptor. Can u help me picture in step by step , i program battery chip and backup firmware

    • Albert van Bemmelen

      March 31, 2017 at 2:20 pm

      Nihar, before you buy the expensive BE2WORKS software you must make sure that the Battery Packs you want to repair and reset have a controller chipset that the program is able to reset. Buying the completely build CP2112 pcb board is not expensive and will help you to read any Battery Pack that the software recognizes. But to know what controller is used you often just have to carefully open the Battery Pack to find that out. Because making a new I2C cable for a Battery Pack that is not supported is rather useless. Everything you need to know is written in the repair article and if you have any other question, it probably is already answered in the posts. About backup the battery firmware, it is not always necessary and was opted by the people of BE2WORS after I had reset one of the Battery Packs in my article (the 8030 chip). It is unclear why you need to Backup anything after a Pack is reset to new at 0 cycles. But saving of Battery data after any I2C read-out is possible. But saving data is often different depending on the Controller and Eeprom used in any Battery Pack.

  6. Albert van Bemmelen

    April 4, 2017 at 3:48 am

    For anyone interested. Here follows my third Battery Pack connector data:
    _(GND) T NC SCL SDA +(11.74V)
    This is the I2C connection for the HP HSTNN-LB42 6-cell Li-ion pack (10.8V 47Wh).

    Use the top BE2WORKS setting : BQ208x and you will be able to read the Battery pack.

  7. Albert van Bemmelen

    April 4, 2017 at 5:06 am

    PS: I just bought a Schwabe 60533 MIXO Einschaltstrombegrenzer , IP44 Gewerbe, Baustelle 16A 230V (German poduct, about 92 euro) to prevent blowing up my 25A mainfuse after switching on my 709A+ 2 in 1 Spotwelder.
    It should perfectly well work because the inrush limiter can handle upto about 3800 Watt of Power!

  8. Albert van Bemmelen

    April 4, 2017 at 9:26 pm

    Small correction, Its maximum Power is 3500 Watt by the way, which is about equal to 16 Amps x 220VAC. See here:
    It is very cheap on Amazone but since I do not have a credit card I paid about 32 euro more at Dutch Conrad. (when bought at Conrad Germany it also is cheaper compared to Conrad in the Netherlands).

  9. Albert van Bemmelen

    April 7, 2017 at 7:20 pm

    Just tested the yesterday recieved Schwab 16A 230VAC Inrush current Limiter.
    It works great !!
    Worth the money for sure!! (So Gerald, it will certainly work at your home too if there also is a USA current Limiter version).
    I only had to change the USA AC plug with travel adapter plug to a decent EU plug on my 709A Spotwelder because the crappy travel adapter (USA to EU) did not stick/fit in the Schwab inrush current limiter!

    • Albert van Bemmelen

      April 8, 2017 at 3:36 am

      New Battery Pack info (Dell J1KND 11.1V 4400mAh 49Wh).
      9 pins connector
      - - nc BE - SDA SCL + +
      Pack could be read with BE2WORKS BQ20ZXX and BQ208x setting.
      Do not know if I am able to reset this pack also because the pack is brandnew.
      (I therefore haven't opened the Battery pack to see what controller is used).

      • Albert van Bemmelen

        April 10, 2017 at 2:31 pm

        Resetting the above mentioned Dell J1KND 11.1V 4.4Ah 49Wh Battery pack was no problem in the BQ208X setting (BQ2084DBT on board).
        Another Pack fixed as new!

        • Albert van Bemmelen

          April 10, 2017 at 2:51 pm

          Oops: Although I probably also am able to reset the above in my post mentioned Dell J1KND Battery, I can not yet confirm this.

          Instead of the above mentioned Dell J1KND 11.1V 4400 mAh Battery, I actually meant to write about the HSTNN-LB42 Battery that was indeed fixed in the BE2WORKS BQ208X setting yesterday.
          And was the actual Battery I intended to write about instead of the Dell J1KND in my above post. If the Dell Battery also proves to be resettable I of course will mentioned it in a following post.

  10. gerald

    April 20, 2017 at 7:06 pm

    Hi Albert,
    since last reply,I was waiting for my spot-welder which I ordered in china with aliexpress.This is basic model called jst III .I just received it today (one month waiting with UPS).Total cost is about 112 euros + 40 euros intax.I thought it was better than buying in UK or Germany but sucks!!!So i will finally be able to change my lithium cells ...Do you have some advice for buying them on the net?

    • Albert van Bemmelen

      April 21, 2017 at 2:00 pm

      I just read your above post Gerald but wondered what you meant by "I thought it was better than buying in UK or Germany but sucks!!!" ?.
      My seller won't send me new yellow caps for both frontarms of my 709 spotwelder machine. And I only have the machine for about 5 months now. So that service from seller accuni-express sucks too! They do not give any decent reply or help! So I hope this message warns others to buy from them. (waste of 250 euro + 28 euro intax!!). And you better use a Schwabe (DeWalt?) inrush limiter too. It not only limits the inrush current but also any over-current while using your machine (over about 2200 Watt). And odd thing I discovered is that even when you in the event of a over-current event remove or switch-off your spotwelder from the inrush current limiter, the limiter keeps getting hot on its internal NTC(s) while continuesly protecting by mot giving any output, until the Schwabe inrush current limiter itself is completely disconnected from the power line. And after about 10-15 minutes cooling down time, depending on how high the over-current was, the limiter will be operating again. About your question on what Li-ions to buy, I bought the purple Samsung 2600 mAh cells. And some of those were even upto 2800 mAh. And one seller sold Samsung cells that only gave about 2100 mAh, which I sadly only discovered afterwards. PS: resetting Dell battery packs with BE2WORKs still never worked. I was only able to read them.

  11. gerald

    April 21, 2017 at 10:33 pm

    Hi Albert,
    I will have a look for inrush limiter,thanks.

    • Albert van Bemmelen

      April 23, 2017 at 3:06 am

      My Schwabe Mixo-Start Limiter (art.number 60533) prevents blowing up fuses higher than 16A, Gerald.
      It is designed for 16A automatic fuses, of the types B, C and L.
      The Limiter can be powered on 2 to 15 times per minute. (depending on the Power that was used). I noticed that when I select more pulses per welding spot in time, my 709 spotwelder has problems with welding parts together quickly because the Limiter starts limiting the current sooner. So I use 2 or 4 pulses max because that seems to work longer before the current gets limited until the NTC is so hot that it stops giving any current completely. I noticed that the power exceeded the 1900 Watt level easily when 4 and 6 pulses are selected simultaneous (giving 10 pulses). Although my spotwelder was described only using about 1900 Watt, it in fact than was more likely over 3800 Watt! When I only press the 6 pulse button it stops at using not more than 2800 Watt. And when I only press the 4 pulse button the power used is around 2000 Watt. It differs depending how fast the Welder arms are activated and how long. And good to know: that is even when you weren't welding yet, but only were activating the welder arms.


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