Generally available Li-Ion 18650 branded and no-name batteries of various capacities were used for testing.
The cells tested come in protected (protected) and unprotected (unprotected) versions.
Pictured below are the batteries tested
Each battery was fully charged with a smart, fully automatic charger Xtar VC2SL before the discharge test
The internal resistance IR (Internal Series Resistance) of the cells was measured using a RC3563 tester
The capacity of the cells was tested using artificial electronic load RIGOL 3021 with a battery test function.
We will carry out a capacity test expressed in mAh (milliampere-hours) by discharging the batteries using an electronic load with a constant current of 1 A to a voltage of 2.8 V.
Discharging Li-Ion batteries below a certain value, i.e. over-discharge, may cause an irreversible chemical reaction and affect the life of the battery. For this reason, cell manufacturers provide a cut-off value for the discharge voltage of the battery ("Discharge Cut-off Voltage"). The values vary, e.g. 2.5V for Panasonic NCR18650A, 2.75V for Samsung ICR18650-26J1. As the no-name batteries do not have detailed technical data, we set the cut-off value for the discharge voltage at 2.8V.
Below are the discharge characteristics of the NCR18650B (3350 mAh) Panasonic battery
For this battery, the discharge cut-off voltage is 2.5V. The discharge characteristics are shown for currents of 2C (6700mA), 1C (3350mA), 0.5C (1675mA) and 0.2C (670mA). The highest capacity can be obtained by discharging the cell with 1C = 670mA. The horizontal dashed line labelled: "2.8V (End of discharge)" shows the capacity differences for different discharge currents. You can see that the lower the current, the higher the capacity.
Below are the discharge characteristics of a 2600 mAh cell to 2.8V with a current of 1A.
The internal resistance of the battery IR (Internal Series Resistance) determines how quickly the voltage drops when the cell is connected to a load. The higher the resistance, the greater the voltage drop. The lower the internal resistance, the faster the battery charges. The batteries we tested were brand new and this parameter did not show anomalies.
18650 cells come in protected and unprotected versions. 18650 battery means: 18 mm - diameter 65 mm - length 0 - cylindrical cell
Most branded 18650 protected and unprotected cells have the following protection:
PTC (Pressure, Temperature, Current): protection against overheating caused by a short circuit, or too high a current. Circuit built into most branded 18650 cells.
CID (Current Interrupt Device): pressure valve that will permanently shut down the cell if the cell pressure is too high (this may be caused by over-charging).
These protections do not protect the cells from over-discharging and over-charging.
Protected batteries use:
PCM (Protection Circuit Module): protection against over-discharge (<2.5V), over-discharge (>4.2V), and over-current. There is a circular PCB with electronic components under the negative pole, so protected cells are about 4 to 5 mm longer than unprotected ones. They may not fit standard holders.
This site uses cookies. More information about using by us cookie files, their usage and how to modify the acceptance of cookie files, can be found by pressing
link