For this part we suggest you to look at the following tutorial :
[http://lowtechlab.org/wiki/R%C3%A9cup%C3%A9ration_de_batteries Récupération de batteries]
''' Voltage measure:'''
We start by measuring the voltage of each cells in order to check if they are working properly. Every cells that have a voltage lower than 3V will not be able to be used in this project and should be recycle.
*Using a multimeter, in DC mode, measure each cells and check the one that are usable ofr the project.
'' Be carreful :'' If the computer battery seems to have liquid on the outside, do not open the box, lithium is harmful in high dose.
''' Measure the capacity :'''
To measure the capacity of a cell, we have to charge it to the maximum and then discharge it.
Those cells are lithium based, and need a specific charge and discharge system, ususally the maximal charge is 4,2 V and the minimum is 3V.
Going over those limits will damage the cell.
*Use a PowerBank : it will alow you to charge many cells at once with a USB port.
*Charge the cells and wait until the charge is complete (all the light should be on), it will be done in about 24 hours. ''(image 3)''
*The cells will be charge at their maximum (4,2V), now we have to discharge them.
*You should use an Imax B6 : a tool that allow to discharge the cells and check their capacity.
*How to use the tool :
*the voltage : it will ask you which type of cells you would like to check, you should choose the lithium one. It will automatically regulate the discharge at 3V minimum.
*the intensity : set to 1A in order to have a quick and secure discharge. In this condition, the discharge should take between 1 hour and 1 hour and half.
*Connect the magnet to the crocodile clips, then connect to the cell, the magnet help to let the current pass through the Imax B6 to the cells. ''(image 4)''
*Discharge the cells until they are completely empty.
*Note the capacity on the cell. The higher the better.
*Sort your cells by capacity : <1000 mA, between 1000-1300, 1300-1500 and >1800 mA.
'''Remark''' : It is important to do homogeneous batteries, with cells that have a similar capacity