Best Charger AA/AAA/9V NiMH for capacity tests according to IEC “Forming Charge”

[Kiriakos GR]

For some time now, I am studying IEC documentation regarding the subject of battery capacity evaluation.

• There is a defined procedure, so the testing engineer to follow.
• They are required, a number of specific equipment.
• There is a specific timing and a pause, between its step to the next.

The process it can begin, as soon the battery this receives a “Forming Charge”.   

From the other hand, IEC this does not giving you any shopping list, and or an advice, of what equipment you should use.
These choices they are primarily related to your own application, and or better explained, for its one DUT type, it is required and a charger with specific potentials.

I am currently interested for three types of DUT.
• AA  1900~2000 mAh
• AAA 750~1000 mAh
• 8.4V  220~300 mAh 

“Forming Charge” this is possible when the charger this can deliver stable current at 1/10 from the named battery capacity for an specific amount of hours.
For my AA DUT I need 200mA
For my AAA DUT I need 100mA
For my 8.4V DUT I need 30mA

Few hours ago I did discover something impressive, there is out there a low cost charger, this combining all three current levels which I need.
This is consumer level, 7 Euros worth product, almost everywhere available. 

[Kiriakos GR]

Break-In Mode (IEC Capacity Analysis)

• Applies a 16-hour 0.1C charge (0.1 times the capacity of the battery), rest of one hour, followed by a 0.2C discharge, rest again, and finally a 16-hour 0.1C recharge again.
• This process is also known as “Battery Forming.”
• The process follows the IEC standard for determining battery capacity.
• The Discharge Mode must be done first before using the Break-In Mode.

[Kiriakos GR]

Approx. Internal Impedance at 1kHz 20ﾟC

AAA 750 mAh ~ 800 mAh
After 3 cycles of charge and discharge under the conditions of:
Charge : 75 mA × 16 hours, Discharge :150 mA(E.V.=1.00 V) at 20 °C

Followed by the  Internal Impedance measurement 1~4 hours later.