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)