The short-circuit of Winston LiFePO4 cell (see from 4:23)
Video shows the short circuit with a direct cable connection over 8 mm bolts in the terminals.
Due to the high current and the relative high resistance of the terminal bolts, the bolts will get extremely hot with temperatures above 1000*C. This high temperature of the terminals will cause the over heating of the plastic around the terminal.
After some time, the plastic around the terminal starts melting and burning with a small fire. This fire is not caused by the battery failure but by the over heating of the terminal.
As the over heating continues, the temperature of the terminal increases and the meting and burning of the plastic case continues. However there is not any smoke and not an explosion.
Conclusion: at the short circuit, the cell does not emit any smoke from inside, does not burn, and does not explode. Due to the high currents the terminals will be overheated and the plastic case will burn as a result. The LiFePO4 is a safe technology.
TEST: The Winston LiFePO4 cell 160AH short-circuit at 1000Amp for 13 minutes
This test proves the safety of the LiFePO4 technology: no fire, no uncontrolled explosion into in fire, no sparking, no burning, no fire smoke (black).
The short circuit on an over-charged cell. This video shows the extremely high speed discharge (nearing the short circuit) of the Winston 160AH cell. To intensify the abuse conditions, the Winston cell was overcharged and become swollen before the short circuit discharge.
The over charged cell has already damaged internal structure (higher internal resistance). Thus the cell will release more heat than a healthy, regular cell with no overcharge.
After 3 minutes of short circuit the temperature of the terminal connectors increases. Due to the high temperature of the terminals, there is a small smoke coming from the plastics case around the terminals.
After 10 minutes the internal temperature of the cell has increased too high. The high temperature causes the gassing of the chemical substances inside the cell and as a result the cell has become severely swollen. More and more gasses start to be released from the safety valve on the top of the cell.
After 12:30 minutes the internal gassing is so high that the gasses start to be released from the safety valve. At this moment the temperature of the cells is around 180 *C and the internal structure if the cell is collapsing. The cell is no more releasing any energy, but most of the energy is burnt inside as a heat.
At 12:40 the release of the gasses from the cell is so high than the cell makes a „trumpet like sound“. At this moment the internal pressure increases to the maximum.
At 12:56 plastic case will no longer withstand the internal pressure and the plastic case breaks out making an „explosion like sound“, with a lot of smoke. At this moment all gasses inside the cell are released at one moment. The cell continues to generate the smoke.
During the short circuit test there was not any smoke with heat and fire (black color smoke). The cell did not set itself on fire, the cell did not burn, the cell did not explode because of fire.
The „explosion“, or rather burst opening, of the cell was because the case (outside shell) of the cell did not withstand the internal pressure. If the cell was in a battery pack, or tightly located in a proper battery case, the cell would keep the shape, as the neighboring cell would not allow the cell to become swollen. In a battery case, the cell would not most likely „burst open“: it would continue to resale the gasses thru the safety vent much longer.
The regular capacity of the cell is 160 Ah at 3.2V. The charging capacity is 160AH at 4V. This makes 640Wh of energy. With some overcharge, it can be estimated that the cell was holding of 700Wh of energy. This energy was released at some 13 minutes of short-circuit discharge. This corresponds of 3250W of immediate power. At 3.2V the short circuit current was about 1000Amp.
Check all details on how to setup a smart house automation system using the mFi.
Some good tips are mentioned in this video
Cheking the Door-Bell Connecting the current sensor to the door bell transformer. If somebody presses the door bell, the current will flow and the mFi will detect it. This can send a message by email or SMS or serve as a trigger for some other appliances.
Garage Door Automation Connecting the mFi to the garage door opening system: when there is a movement in side the garage in between a certain time in the morning, it means we are to leave the garage, the door will open automatically. The door will close when no more movement is detected.
The RT-BMS is in Stand-by model. By powering the “System Switch ON” (the F connector), the RT-BMS turns on into the operation mode. The Master unit displays the lowest (d) and highest (c) voltage of the battery pack. (In the video the values are: c 3.29V, d 3.26V). The signal lights turn on for 1 second to verify the bulbs are functional. The signal lights are as follow: blue color - connected to “A3” for Error, yellow color - connected to “A4” for Fuel Reserve (Low Capacity). Onboard LEDs show the connection of the power disconnecting switches: LED B3 - Main Current (for motor controller), LED B5 - Main Charging, LED B6 - High-Speed Charging.
When the power source is connected, the RT-BMS Master units performs the power-up sequence. During the power-up sequence the RT-BMS Master unit checks all the possible modules addressing, counting from 000 to 064, 128 or 192. (In this demo it is 128). Then it displays the total number of modules found. (In this demo it is 004). After the power-up is finished the RT-BMS Master unit turns off into the Stand-by mode. The Stand-by mode is controlled by the “System switch On/OFF” - the F connector.
Quoting: This week we digress a bit from vehicle issues and take a look at the progression of LiFePo4 cell offerings over the past two years. We also do some full 1C discharge and charge tests on the cells. See more here.
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