Make a Cheap Lithium Battery Pack

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Introduction: Make a Cheap Lithium Battery Pack

With some few hacking, you can turn your old phone battery into a powerful Lithium battery pack. This is a great alternative for the expensive Lithium-Polymer battery packs. These things work well with Arduinos, DIY robots, speakers or any project that requires a high current power source.

What's The Secret?
The secret is simple. Obviously, phone batteries are designed to work with phones. A fail-safe circuit is added on top of the battery to prevent the battery from draining too quickly, overcharging and exploding. By removing the limiter, you'll be able to get full power out of those mobile batteries.

Why Upgrade To Lithium Batteries?
Lithium batteries are one of the most powerful batteries existing today. They are small in size, they have high charge capacities, and also have a high "c" rating. Lithium batteries are 6x-10x more power than AA (NiCd/ NiMH) batteries.

My Top 5 Project Application:
1st.) Robots & Drones
2nd.) Compact Speakers
3rd.) Arduino Projects
4th.) Compact DIY Gadgets
5th.) Solar Powered Reservoirs

Video Tutorial & Discussion:


I used the battery pack on last year's National Robotics Competition.
I was happy that I won 1st place in the championship with it! :D


Stay tuned! More Projects To Come!
I just got back from our vacation in the beautiful islands and beaches of Palawan :) I'll be posting a series of projects this month, including my: DIY CNC Build, Electricity Generating Footwear, 7 Homebrew Arduino Sensors, High-Precision Obstacle Robot and 10 other projects waiting in my draft list :)

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WARNING: This is a dangerous project! There are risks in attempting the hack. I or site is neither liable if any of you gets injured. Don't forget to wear safety gears like eye-protection and gloves. Lithium batteries are prone to explosion. Before attempting the project, make sure you have enough experience over these batteries and don't forget to drain them.

Step 1: Finding Good Batteries

If you still have those Nokia batteries lying around, you might wan't to put them in good use. If you don't have any, generic batteries work fine. I got mine from CD-R-king and bought each battery for 100php ($2 ). DX.com is also a great place to buy generic batteries, they sell them cheap.

Here's the exact battery that I bought: MOBILE PHONE BATTERY (BL-5C 1000MAH)

Step 2: Peel and Remove the Label

Carefully peel the battery's label. 

Step 3: Clean the Battery

The label leaves a sticky residue, it's a bit eyesore so I tried to remove it. I used a clean piece of cloth and few drops of handwash alcohol to quickly remove the stick stuff.

Step 4: Open a Small Gap

Use both of your thumbs to open a small gap on the battery's head, large enough for your hobby knife to fit through.


Don't worry, it's not what you think it is. The cover/ cap on top is actually a circuit and not the lithium battery's cover. The battery would not explode once removed, well not unless you short the Lithium battery.

Step 5: Remove the Limiter Circuit

Get your Leatherman multitool then use the knife to slowly remove the metal connectors. Remember to keep the metal ribbon connectors intact, you'll need them since the battery's terminals are made out of aluminum. Materials made from Aluminum can't be soldered. Those metal ribbons are your only chance of soldering wires on your batteries.

Step 6: Insulate the Batteries

Don't forget to insulate each of your batteries with tape. Their aluminum bodies are actually conductors of the positive lead. This is done to prevent the batteries from shorting.

Step 7: Making Packs: Soldering Them in Series

After insulating each battery with tape, you can now start to stack them! 

Battery Basics:
You can increase the current by soldering the batteries in parallel. Soldering them in series makes the voltage much higher.

Series Connection:
1 cell   = 3.7v   (1000mAh)
2 cells = 7.4v   (1000mAh)
3 cells = 11.1v (1000mAh)
4 cells = 14.4v (1000mAh)
5 cells = 18.5v (1000mAh)

Step 8: Special Chargers

These batteries need special chargers, also known as balancing chargers. Lithium batteries are sensitive to overvoltage. 

Step 9: Test Them!

I used the battery pack on last year's National Robotics Competition. I was happy that I won 1st place with it.


My 2014 Version Of My Sumobot (MiniSumo). It's much smaller and has a low height of 3cm!

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  • I have made one. Gre...-chienline

    chienline made it!

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92 Comments

another source of good lithium ion batteries are laptop batteries, i do dismantle a lot and choose the good ones for my projects.. i made a charger using lm317 voltage regulator i.c. as the charger electronics..

I find them good for many uses. BTW, I've found that MOST of the discarded laptop battery packs still have most of its cells in still a very good condition (!)...

I've even found perfectly good ones, but INTERESTINGLY ENOUGH, the laptop was insistently giving very frequent pop-up messages about "The battery is almost empty, connect the charger immediately..." After opening up the pack that the owner gave me (as he was convinced it was toast), I found ALL the cells charged above 90% (!)...

So, I have several possible theories:

a) the messages are bogus, and are meant to induce the laptop owner to quickly go the the nearest store and buy a new one, which will improve the manufacturer earnings, specially since their prices are way too high for an "original x-Brand battery pack"...

b) The battery may have an "intelligent chip" that tracks either: date, number of charging cycles, or number of hours... and fires up the urging messages that pretend to mean: "you NEED a new Battery"...

c) An overly "creative" electronics "designer/programmer" decided to cheat on the consumers, and just placed a bit of software in order to improve its employer earnings, at the same time he/she lightens their customers wallet...

Pick your favorite or add your own theory.

But the fact remains: Nowadays is too easy (and tempting) to cheat on the unsuspecting consumer and then go for his/her money. Already, big companies like Panasonic have cheated on their customers (the infamous case where their famous Plasma displays underwent completely undesirable and (fraudulent) contrast loss -programmed to occur after the TV set was sold-... As Toyota, GM and other companies, they denied any wrong doing. But the fact is that the Firmware of the Panasonic Plasmas was simply following its programmed instructions: to reduce the contrast of the plasma. Soon, the discerning owner noticed that the famous "ultra-deep" blacks were disappearing... but the Factory kept saying the panels were "working to specs". That is the reason I'll hardly consider to buy another Panasonic product. That resulted in a class-action suite, but the owners received very little money and Panasonic lost a large sum for their lack of integrity.

Anyway. The 18650 cells that came from a Sony Laptop pack were all OK, mesuring above 90% of their rated capacity, voltaje and were almost perfectly balanced, but the laptop was displaying the messages all the time. After carefully disasseembling the pack (which has a very thin plastic ribs separating the cells and their wiring from a dead short circuit) I used them to power an old cordless hand drill (B&Decker) and gave it new life and added power). Another pack (from a Dell laptop) was very similar, and its cells now power my flight pack (I fly R/C model airplanes, replacing the very heavy and cumbersome lead-acid 12 V gel cell used for starting the glow engines at less than a fraction of the weight and bulk! Amclaussen.

How do you open laptop batteries? Dremel? Sharp knife?

user

Hammer. Definitely a hammer.

Sorry J,R,D, Ltd...: I was busy and your question went unnoticed by me... anyway, please read carefully: PLEASE BE EXTRA CAREFUL WHEN OPENING A LAPTOP BATTERY PACK!!! I've used a combination of Xacto and not so sharp screwdriver's tips to pop open the small tabs holding the pack halves together, after cutting/scribing the ultrasonic welds... BUT keep a sharp eye (protected by googles, btw) on the insides of the pack, as I've seen at least one from a Sony Vaio laptop, that had only some plastic partial ribs separating LIVE metal strips from making a dead short circuit, of the worst kind! But being REALLY careful, and finding WHICH side of the pack should be down against the table, and which should be up, helps in avoiding nasty shorts! Good Luck! Amclaussen.

That's alright. I actually forgot about this comment, hehe. Thanks for the info.

"MOST" of the cells are still good.

You goon and on with your theories about companies abusing their customers, but did you ever stop to think about why the battery would report that it is bad if only "most" of the cells were in good condition?

Laptop batteries are usually configured as 3-series of 2-parralell lithium ion cells.

The batteries aren't user serviceable (and shouldn't be!), to replace one cell isn't a matter of going to the local store and buying a replacement and popping it in... Even slight voltage differences can cause serious problems with multiple lithium ion cells connected together. The worst case scenario being a firey explosion.

Likewise you can't just toss any lithium-ion battery pack in any device and be safe knowing that nothing bad could happen. Even if the batteries are the same voltages (which at most is all a regular user would check).

Its not a "smart chip" pulling one over on customers, and it's not so OEM's can make more money. It's so that people who aren't amateur/professional electronics engineers can't hurt themselves doing something they've all grown used to when it comes to devices and batteries.

While you may have noticed that the batteries were charged 90%, that doesn't necessarily mean anything. mAh is what really matters in batteries...

When laptops start to get older, the chemistry within lithium ion batteries starts to change. Their internal resistance also goes up as they age, meaning they can't source as much current without either 1. Overheating, or 2. Simply not being capable of doing so anymore, since their capacity has dropped so much.

You are right on the cycles part; the uC inside of the battery counts how many discharge and recharges the batteries go through. Usually after so many the batteries start to drop in performance, enough to the point where you have to keep your laptop plugged in more and more.

OH YES: IT MEANS that the batteries really HAD about 90% of their full CHARGE still inside them!... I never said "voltage" or "apparent charge", but REAL CHARGE, measured by a dedicated charge counting intelligent charger (a Triton-2 unit, made for aeromodeling uses, capable of charging NiCads, NiMH, Li-Ion and Lipo's, and even Lead-Acid batteries, this charger shows measured mAh as it charges, discharges or cycles the batteries. My Triton-2 carger has been upgraded by replacing the input and output cables and alligator clips, and by going to extremely heavy and short cables, the voltaje drop is negligible! (a couple of millivolts, to be precise...) amclaussen.

BTW: after several years of extra life use, one of the cells in my cordless drill started to show its degradation, at last. But the thing is: the damn Laptop kept showing the IMMEDIATE "need to connect the charger NOW.." message, but that message was a complete FRAUD!, as the performance of the "ended-life" battery cells was still excellent.

Yes u are so correct, i got lots of used laptop batteries from my old laptops, most of them, when i dissambled, the cells are still good, had some power my screwdriver, charcoal blower, toys and some electronic experiments.