Need some compact power for your Arduino project?

Need some free rechargeable batteries for your mobile gear?

Want to add some awesome to your interactive art?

What would McGuyver do?

This instructable shows how to modify a typical Samsung battery charger to become a compact module that can be used to charge any Samsung battery, as well as a few others that aren't from Samsung...

The result is that you can easily rotate a set of batteries for you projects, plus you can collect and reuse discarded cellphone batteries, which likely would not have been recycled otherwise.

You will need:

A set of "Dupont" jumpers in the right colors (3x females, cut in half, plus a set of 3x males) (Ebay)
Wire-strippers
A single zip-tie
Some super-glue
A Samsung battery charger module with micro-USB
Some Samsung batteries

If you don't have any Dupont jumpers, you should splurge and buy a few dollars' worth - they are insanely useful things! Get them in Male-Male, Female-Male, Female-Female, in 20cm and less.

Step 1: Getting to Know Samsung Chargers

This project assumes you have a handful of old Samsung chargers lurking around.

Although it is possible that other chargers can be modified in exactly the same way, don't assume this is the case.

Adding a Connection

Samsung batteries have three terminals, and four if they also contain a built in NFC antennae. Both can be used. You are concerned about three terminals - the positive (marked + on the battery), the negative (marked - on the battery), and the middle, unmarked terminal. this is called the Thermistor connection, and is used to measure battery temperature, probably so that nothing horrible happens while it is being charged.

In the either type of battery, you will solder a wire to each of these three terminals, leaving the outer unmarked connection alone. Do it quickly, otherwise you will melt the battery casing, damage the protection electronics, or if your soldering is rEaLlY bad, turn the battery into a smoke-bomb. This is what we refer to as "A Bad Thing".

Why bother with a Thermistor connection?
Because the charger will not function unless it is connected to all three, so you need to make connect the battery as if it was slotted into the charger.

Cut the female jumpers in half.
Strip the ends of the jumpers.
Solder a female red jumper to battery positive, a female black jumper to battery negative and the extra color female jumper to the middle thermistor terminal. Quickly! Quickly!
Snip off and extra pointy bits, and add some tape over the terminals to protect them.
Battery module, reporting for duty (er...cycle)!

Step 2: Connecting to the Charger

The spring terminals on the battery charger module (or the exposed board) correspond with a battery that has been inserted into the module.

Strip the ends of the remaining female jumpers.
Solder a female red jumper to charger positive, a female black jumper to charger negative and the extra color female jumper to the middle charger terminal.
Make sure that none of the wires are touching. Its delicate work, but not too difficult with a clean soldering iron and a steady hand.
Add a drop of super glue to hold the wires in place to the module. This also keeps them from moving and touching each other.
Bundle the three color-coded male jumper wires together, twist them nicely, and zip-tie them.
Cut the zip-tie so that a length remains, and glue it to the module. This will serve as a charging cable. By not gluing the actual wires down, the wires can be cut loose and used again someday.

Why bother with female connectors on the battery and charger, with male wires added in between?

This serves to increase safety, because you're forced to carefully connect the right colors each time you wish to charge a battery, and when done you can disconnect the setup, leaving the charger and battery isolated once more. Remember, both the battery and charger can provide current to anything contacting with their terminals, so by embedding the terminals within female jumpers, we can rest assured that they will be safe, even bumping around in a backpack with car-keys.

Step 3: Check Your Charger

Connect everything up (battery red to charger red, battery black to charger black, battery ...other color to charger...uh...other color.)

Plug in a micro-USB cable, put that into a USB charger, put that into a socket and (boom?) voila!

Your charging rig is ready.

Assuming you didn't pick up a dud battery, the charger will flash green, orange, then red.

Red stands for "This battery will be Red-y when I say so!"
Green stands for "Oh my goodness, its good-to-go."
Orange stands for "Oh, rae-lly? Odd battery..."
The very rare, sparklepuff-colored LED flashes on the 999999th time you charge a Samsung battery. It unlocks battery God-mode, plus all the charger hidden easter eggs.
Orange-yellow flames are an indicator that the charger is ready to be unplugged. Like. Right now.

A typical charge should take about an hour or so.

Step 4: Build and Power Something Sick and Cool

Once you have some batteries and the means to charge them, it really makes your projects mobile.

Suddenly, you can power an Arduino somewhere remote.

Suddenly, you don't need to buy AA batteries anymore for you projects.

Suddenly, you can build rechargeable torches with ease.

This is an easy project that anyone with the will, careful attention to detail, and basic soldering skill can do first time - its not rocket science. Its well worth it, and you are turning what would have been a waste product into something very useful.

This project is part of a contest, so if you liked it, please vote for me!

If you didn't like it, vote for me anyway!

And if I made any mistakes, if you have questions, if you have something cool to teach me about Samsung battery chargers, or ideas for ways to take this further, please say something in the comments!

Love, Paul