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Harsha Alva
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Mechanical Engineer + Software Developer (Project Leader)
 · MangaluruIndia
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TUTORIAL

Extracting 18650 size Li-ion cells from a laptop battery

Warning
Do not try this at home. There is a serious risk of fire and/or explosion.
I’m not responsible if you were injured while doing this.
Unless you know what you are doing, don’t try this, like seriously.

 

Earlier today, I found my sister’s laptop’s old battery. I was supposed to throw it away, but since I’m a scavenger, I decided to open it up.

 

Things required

  1. Old laptop battery.
  2. Safety goggles.
  3. Flat head screwdriver.
  4. Box cutter or kitchen knife.

 

Safety

  1. Exert force judiciously.
  2. Sharp tools may cut you.
  3. Battery may explode in your face, worst case scenario.

 

Steps

I followed this video on YouTube from start to end.

 

End result

Found 6 Li-ion cells in a 3S2P matrix. They were in a good condition. But the cell-to-cell connections were damaged during disassembly.

 

Notes

  1. Was I scared?
    Hell yeah! My body parts aren’t replaceable.
  2. Did I see sparks?
    Yes. When I drove the screwdriver into the battery, it shorted out something on the BMS (Battery Management System) circuit.

 

See this thread to learn how these cells could be used to make a battery pack.

#Robots #Robotics

Electrical Engineering
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Harsha Alva

For educating us on Battery packs and how to charge them. Very useful experiments

Harsha Alva

A great hack by Harsha

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Steven Reubenstone
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Mechanical Engineer & Tinkerer of Things.
 · New YorkU.S.
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great post

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Harsha Alva
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Mechanical Engineer + Software Developer (Project Leader)
 · MangaluruIndia
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Ravi Pujar Do you know about any ready to use PCB that I could use these cells with?

Functions I need:

  • Li-ion 18650 size cells in 3s2p configuration. So 3.7V * 3 = 12V
  • Low voltage cutoff.
  • Short circuit protection.
  • LED indicators for full, medium, low state for each cell.

I have found a board that does most of the above work here, but it needs a 14V charger, and there’s no balance charging feature and no indicator for each cell pair.

How do I add such an option to this board?

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Ravi Pujar
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Embedded systems engineer, Founder @Valetron Systems, Blogger @www.raviyp.com
 · DharwadIndia
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Hi Harsha Alva
Sorry i havent worked on multi cell lithium batteries before. So i am not familiar with the concept of balanced charging (Learnt from google now ). But we can use Lithium battery fuel guages like one mentioned here
http://www.ti.com/lit/an/slua300/slua300.pdf. Texas instruments BQ series has complete solutions for these applications. I came across BQ24618 but didnt find balanced charging option mentioned anywhere clearly.
Again, these are chips on which we need to build upon. I havent came across readymade boards though. Will be following you to learn more on this :)

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Harsha Alva
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Mechanical Engineer + Software Developer (Project Leader)
 · MangaluruIndia
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Ravi Sorry I forgot about this thread.

Thanks for the TI link. I’ve chosen TP4056 charging board.

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Ravi Pujar
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Embedded systems engineer, Founder @Valetron Systems, Blogger @www.raviyp.com
 · DharwadIndia
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Harsha Good choice. VALTRACK V1 used TP4056, its very cheap. So you are tapping out individual cells and charging them ? Because TP4056 is a single cell charger.

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Harsha Alva
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Mechanical Engineer + Software Developer (Project Leader)
 · MangaluruIndia
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Ravi Yeah. I’ll be using 3 boards in parallel for a 3s battery. Will come up with a schematic for the charger soon.

In the meanwhile, check out this thread https://www.collaborizm.com/thread/BkfnAA70l?utm_content=menu_share&utm_source=user_Hyt3y6XK

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