Battery pack repair tips

Very many battery packs are built using standard size cells inside the plastic package. When cells go bad, it is often possible to replace the cells with new one either as DIY project or have some repair company to do that. Usually my option one is to find replacement battery for devices, and if it is unavailable or terribly expensive, consider putting in new cells. Building the new battery pack needs some knowledge and right tools (small spot welder and/or soldering iron).

Cordless Drill Battery Pack Rebuild for $20 or Repair for $0: Nicd Battery Pack Rebuild

Total cost at time of rebuild was $22.54 to rebuild the entire 14.4V Pack with better than original batteries.

How To Rebuild Your Old Rechargeable Battery Packs with new ones. CHEAP!

Repacking Makita 18v Lithium battery with New Cells (Save $$$’s)

Warning: Trying to fix battery without knowledge to do it right can lead to more damaged battery pack, damaged device being powered and possibly start a fire


  1. Tomi Engdahl says:

    Charging NiMH cells – smart vs dumb chargers

    A brief summary of NiMH cells and their charging techniques, and why smart chargers are usually not so smart.

    This video is especially handy because Clive has also briefly discussed different battery technologies from Ni-Cad, Ni-MH, Li-Ion, and Li-Fe-Po . I hope the search algorithm recognises this as well, so as to direct more viewers to this helpfully informative video – and the channel.

  2. Tomi Engdahl says:

    Are AA NiMH Batteries obsolete? Here is everything you need to know about them!

    EEVblog #35 2of2 – NiMH and NiCd Battery Charging Tutorial

  3. Tomi Engdahl says:

    Battery Type Comparison || Lead Acid VS NiMH VS Li-Ion VS LiPo

    In this VS episode I will compare the gravimetric and volumetric energy density and the price of lead acid, NiMH, Li-Ion and LiPo batteries with one another. I will also talk about how dangerous each battery type can be and what kind of battery you should get for your next project.

  4. Tomi Engdahl says:

    Make your own Li-Ion Battery Pack

    In this project I will show you how to combine common 18650 Li-Ion batteries in order to create a battery pack that features a higher voltage, a bigger capacity and most importantly useful safety measures. These can prevent an overcharge, overdischarge and even a short circuit of the batteries.

    More project information (parts list, pictures,….) on Instructables:

  5. Tomi Engdahl says:

    HACKED!: Old laptop battery becomes a Power bank

    In this episode of HACKED! I will convert a battery from an old laptop into a power bank which can charge my phone 4 to 5 times with a single charge.

  6. Tomi Engdahl says:

    DIY Laptop PowerBank (battery pack to charge your laptop on the go)

    In this project I will show you how to create a Laptop PowerBank. It mainly consists of a Li-Ion battery pack and one buck and boost converter. This way the PowerBank can get charged up through the Laptop power supply and aftewards charge up the Laptop directly to give it an additional run time of 3 hours. Let’s get started!

  7. Tomi Engdahl says:

    Building a USB Type-C PD Powerbank the Super Simple Way || Testing an Aliexpress PCB!

    In this small project I will show you how to create a DIY USB Type-C PD powerbank the super simple way. To do that I will firstly test a powerbank PCB based around the IP5328P IC I got from Aliexpress. The measurements will show us how suitable the PCB is for creating a DIY powerbank. Afterwards I will then show you how I created a Li-Ion battery pack and a custom 3D printed enclosure before I will put all the components together to form the powerbank. Let’s get started!

  8. Tomi Engdahl says:

    When Battery Rebuilds Go Wrong: Understanding BMSs, Spot Welders, And Safety

    Batteries are amazing. Batteries are horrible. Batteries are a necessary evil in today’s world of portable everything. If you’re reading this sentence, even if it’s not on a mobile device, somewhere there is a battery involved. They’re that ubiquitous. There’s another thing batteries are: Expensive! And at $350 each for a specialized battery, [Linus] of Linus Tech Tips decided to take battery repair into his own hands.

    Rather than do a quick how-to video about putting new cells in an old enclosure, [Linus] does a deep dive into the equipment, skills, and safety measures needed when dealing with Lithium Ion cells. And if you watch the video through, you’ll even get to see those safety measures put to good use!

    This should be illegal… Battery Repair Blocking

  9. Tomi Engdahl says:

    Building A Spot Welder From 500 Junk Capacitors

    [Kasyan TV] over on YouTube was given a pile of spare parts in reasonably large quantities, some of which were useful and allocated to specific projects, but given the given the kind of electronics they’re interested in, they couldn’t find a use for a bag of 500 or so low specification 470uF capacitors. These were not low ESR types, nor high capacitance, so unsuitable for power supply use individually. But, what about stacking them all in parallel? (video, embedded below) After a few quick calculations [Kasyan] determined that the total capacitance of all 500 should be around 0.23 Farads with an ESR of around 0.4 to 0.5 mΩ at 16V and packing a theoretical energy total of about 30 joules. That is enough to pack a punch in the right situation.

    What can be made from 500 capacitors ?

  10. Tomi Engdahl says:

    DIY Spot Welder with Discrete Components
    This capacitive discharge spot welder operates without a microcontroller.

  11. Tomi Engdahl says:

    Making “MILLIONS” of AMPS of Current

    You can make a ton of current modifying a transformer, but with little voltage, it means little!

  12. Tomi Engdahl says:

    How Does a Spot Welder Work? Review, Teardown and Analysis of a BIFRC DH20 Battery Spot Welder

    In this video, I discussed the principle of operation of the BIFRC DH20 spot welder and demonstrated its capabilities. I also did a teardown and analysis of the unit. Product link:

    00:00 Overview
    04:59 Welding test with different settings/tips
    08:22 Principle of operation
    12:20 Output waveforms
    15:52 Welding current measurement
    19:13 Teardown
    22:12 Conclusion

  13. Tomi Engdahl says:

    The $16 battery tab spot welder

    I’ve been looking for a cheap battery tab spot welder for 18650 lithium-ion cells for awhile now. The usual ones just aren’t worth the cost. Enter the $16.99 Portable Mini Spot Welder! At that price, it was worth a shot. Will it sink or swim? Watch to find out!


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