As the previous repaired 6632B Power Supply is able to sink current up to 5A, I tried to characterize some Li-Ion cells by discharging with constant current, while getting the measured Voltage and Current back from the supply over GPIB using remote sensing. A fuse has been added in series for safety reason, to prevent damage from accidental firing of the SCR circuit, which shorts the output of the supply in the event of overvoltage.
First test in Figure 1 was a LG ICR18650B1 with a nominal capacity of 2600mAh according to the datasheet. The one I tested has a datecode of the year 2010 and was part of a defective Dell laptop powerpack. With the 500 mA standard discharge rate specified in the datasheet, it was possible to get 4670 mWh from the battery, which corresponds to 1262 mAh@3.7 V. The remaining capacity is 50% from nominal. The voltage at the terminals was 4.16 V unloaded and after connecting the load about 3.9 V, which corresponds to an internal resistance of roughly 500 mOhm. When drawing more than 1.4A the voltage drops therefore under 3V.
