DIY: USB battery charger

I have a spare BL-5C Nokia battery I sometimes use for my "DIY" projects. Every time the charge runs out, I have to put it in a compatible phone and use the AC charger to charge it. I'd read about charging batteries using USB and decided to give it a shot.

Things I used:
1- A piece of thermocole
2- USB cable from a broken mouse
3- Two paper pins.
4- Thin wire from IDE cable.
5- Cutter
6- Fevicol


- First I destroyed my useless Microsoft mouse and extracted the cable. I needed only two wires: the red one (+) and black(-).



- I then drew a rough diagram on paper for the charger body. The dimensions of the battery holder and the placement of charger pins is very important. Here's the rough design sketch:


- I then proceed to implement it on perhaps the most easily available crafting material of all- Thermocole. I remember how I used to cut out rectangular shapes, mark some buttons with sketch pens and play around with them as cellphones, calculators and even laptops!
The shape is pretty straightforward. A rectangular slot cut precisely to the dimensions of the battery. I gave a few millimeters headroom for the contact pin assembly.

- For the pins, I cut a thin strip from a non dust eraser. I wrapped one thin wire from the IDE cable to each of the paper pins and securely inserted them through the eraser strip taking care about the distance between them. That was important.

Batteries have a third contact in the middle used for identifying battery type. Something to do with phone compatibility but of no use while charging.

- I attached the wires to the USB wire in the correct polarity.


- Then used plenty of fevicol to prevent loose connections that are so very common in my projects.



Finally, after a coat of cheap black sketch pen and some red...




The charger is working fine but taking a little too long for a full charge. I built another one to be used in reverse as a battery enclosure. This one is neat: