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2000mAH Lithium Ion Faulty In Battery Pack

By on September 22, 2018
battery pack repair












A customer, a good friend of mine came to the shop and was carrying a Makita drill set. As he explained the problem; one of the battery packs was completely dead. When pushing the test button on the battery, it does not show any sign of life.

drill battery pack repair

As you can see, it is 20 volts, 2.0 amp rated battery.

The only way to find out what is wrong, I had to open it and check what is wrong. Let the repair begins.

how to repair drill battery pack

It is as easy as it looks, only four screws to come out and I was able to see inside this battery pack.

how to fix battery pack

It is in very good conditions but that did not stop me from checking over for cold soldering joints or loose connections. All checked out fine.

My mind was set of the batteries inside this pack and in order to get to them, I have to solder these six soldering joints to get there. I de soldered them all and look what I found.

lithium ion battery repair

I wanted to disconnect the batteries and check every one on its own because I had that feeling that one of the batteries is faulty and since it is connected in series it will affect the performance of this battery pack.

lithium ion battery check

As I was individually checking the batteries, all of them checked fine except one.

The value of every battery is 3.6 volts.

lithium ion battery problem

As you can see, the bad battery is found and now it needs to be replaced.

2000mah lithium ion battery

As you can see, I already added the replacement battery which is the pink battery. In order to do that, you have to lift the black plastic piece off and put a new battery in and then re solder all the joints to have a solid connection and that is what I did.

2000mah lithium ion battery bad

This is the old faulty battery that was replaced with the same specification battery but different color. I know pink and blue do not match but once it was covered, nobody will notice the difference.

2000mah lithium ion battery need replacement

I know it looks ugly with that soldering job on these batteries. I need a spot welder for this kind of job. I have seen homemade spot welder built from scratch. Someday I might be able to build one for my shop.

repaired drill battery pack

As you can see, the battery pack is alive and well. The customer charged it and used it on his drill and it worked fine. Mission accomplished.

This article was prepared for you by Waleed Rishmawi, one of our ‘Master Authors’ and currently working in the Bethlehem area of Palestine repairing electrical and electronic equipment.

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  1. Parasuraman S

    September 22, 2018 at 7:17 am

    Very good job! Very sincere approach and resolving!

    • Waleed Rishmawi

      September 25, 2018 at 1:50 pm

      Parasuraman: thank you.

  2. Albert van Bemmelen

    September 22, 2018 at 12:12 pm

    Although you successfully fixed the old pack you were lucky that the battery pack had no cycle count protection chip on-board. Because that would have required you to also buying a new replacement charger board since those boards do not accept replacing the pack after the bad function is digitally 'recorded'. Which is often the case when repairing original Manufacturer's battery packs why those special replacement charger boards are available through China sellers, including universal replacement charger boards that fit easily in any original pack. Soldering lithium-ion cells is dangerous for you and the cells because they don't act well on heat and may explode or create fire why these charger boards normally also have an integrated temperature sensor. I specially bought a SUNKKO 709A spotwelder and pure nickel strips for these Lithium cells including a Mixo InRush Current Limiter. The Schwabe Inrush current limiter protects my main Powerfuse which is only 25A because my SUNKKO easily takes well over 4800 Watts when welding because of the extreme In-rush current! Normally my 230V outlets are only capable at giving max 3600 Watt safely! Burning the main power 25A fuse must be avoided because of the very expensive replacement bill involved which may be 540 euro or more! Officially they registered that we have 35Amp main power fuses installed in each apartment but they are in fact only 25Amp in reality!


      September 23, 2018 at 1:23 am

      Hi Albert,

      good to have your complimentary comments and the info on the spot-welder. I do have concerns that if you limit the in-rush current you may affect the depth of penetration and quality of the weld. In the UK we normally have 80A or 100A supplies into our homes and the Supplier's fuse is to BS1361 whose basic rating would handle 4.8kW loading without an issue. Furthermore the fuse's melting characteristic would give sufficient period of overload to handle a short current burst for the arcing process. It might be a good choice for a future article? especially the charger control boards.

      • Albert van Bemmelen

        September 23, 2018 at 3:52 pm

        Hi ANTHONY, I have no choice and do have to limit the Welder's current because even when I do not weld but just have the Welder connected it consumes a lot of power! Which probably also goes much higher than the mentioned 4800 Watt, why my Inrush converter gets hot internally quickly and I have to wait 45 minutes or so until it cools down enough. AND I have to remove the Inrush limiter from the power 230VAC line too because it won't cool down if I leave it plugged in, even if I do not weld in the meantime. That is also why I need to limit the Pulses per second to finish the job successfully. And I do not want to pay these absurd prices for upgrading my home power box, especially if I could do it easily myself but am just not allowed to do. (also because I only rent my apartment and do not own it.)

  3. Mihai

    September 22, 2018 at 12:12 pm

    Well done Mr. Waleed ! Thank's for sharing.

    • Waleed Rishmawi

      September 25, 2018 at 1:53 pm

      Mihai: you are most welcome.

  4. Anthony

    September 22, 2018 at 12:16 pm

    Hi Waleed,

    A friend in need is a pain in the arse!

    Informative article, as usual, but I must correct the '2 Amp battery'. It is a 2Ah - which is its CAPACITY and not its current rating. You will note that the old battery was marked as '2000mAh'. In practice the battery will deliver 10s of Amps; especially when under heavy mechanical load.

    Keep the articles coming . . . .

    • Waleed Rishmawi

      September 25, 2018 at 1:58 pm

      Anthony: I stand corrected. thanks for your input about it.

  5. Yogesh Panchal

    September 23, 2018 at 3:54 pm

    Good Job! waleed

    • Waleed Rishmawi

      September 26, 2018 at 4:19 pm

      yogesh: thank. I appreciate it

  6. Henrique Jorge Guimarães Ulbrich

    September 24, 2018 at 7:21 am

    Very good maintenance job, Waleed. Albert is right. Batteries suffer a lot from warmth. Using a spot welder is the correct way. All can see how to build a home-made spot welder using microwave oven transformers. See at these two articles: and


      September 24, 2018 at 4:01 pm

      Hi Henrique,

      Great videos and a very good reason to visit the re-cycle centre to find an old microwave oven transformer. The second video showed a great metalworker who was very skillful with a cutting disc in an angle grinder and fabricating brackets - most enjoyable watch.

    • Waleed Rishmawi

      September 25, 2018 at 2:01 pm

      Henrique: yes, I know spot welder is the way to go but so far, I do not have that so the best way is to do it the hard dangerous way. so far so good. the customer is happy with the repaired battery pack so far. yes, I have seen the microwave transformer spot welder on the net..I am thinking of buy a professional one when I go to the USA this year. if not, then I will build one at my own shop.

    • Waleed Rishmawi

      September 26, 2018 at 4:21 pm

      Henrique: thanks. Yea I know he is right but for the mean time, I will do it the old fashion way, till I get myself a spot welder or build one in the shop when I have time. thanks for your input.


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