EverExceed have recently introduced a new technology of low temperature
Lithium iron phosphate battery, which can be charged even under 0°C and in negative temperature. In a series of 5 technical articles we are going to elaborately describe the details of this revolutionary technology. In this article we are going to talk about the last parameter, “Pack improvement” of the low temperature technology lithium battery.
Pack improvement:
Under the cold weather, the normal use of low temperature cannot be met simply by the improvement of lithium-ion cell, when it comes to the improvement of low temperature performance, the last level is pack. The improvement of pack can be carried out from three angles.
Low temperature protection of main engine & amp; protection board
Due to the irreversible damage of low-temperature charging to the battery, the simplest way to improve low-temperature charging is: both
However, if you can't charge at low temperature, don't charge at all.
The main idea of low-temperature protection is to measure the external temperature through the thermistor NTC of the protection plate and measure the measured temperature feed back to the main control chip of the host or protection board. When the monitored external temperature is too low for charging, the host or
The main control chip will cut off the charging function.
In this process, NTC, as a device for measuring temperature value, its resistance will change significantly with temperature after measuring the resistance of NTC, the corresponding ambient temperature value can be obtained.
After the NTC feeds back the temperature, the main control chip of the host or protection board will operate at a specific temperature according to the previously set program.
External circuit heating
For the power battery, it is obviously unrealistic not to allow low-temperature charging. In order to ensure it’s charging at low temperature, you can only heat the battery.
The scheme of external circuit heating is mostly seen in various power battery patents, and the main way is to add one in the battery circuit.
For PTC heater and heat exchanger, when the external temperature is too low, the charging current only flows through the heater, and the rear heat exchanger will heat. The amount is transmitted to the cell, which is in a sleep state before the cell temperature rises to the target temperature. The schematic diagram is as follows:
Inner loop heating
When the heating device is located outside the electric core, the heat transfer speed will naturally be very slow. If each cell is equipped with a heater, the improvement of heating efficiency will be extremely significant.
For self heating cells, in addition to the conventional positive and negative circuit, an "internal heating circuit" needs to be added.
When the external temperature is high, the internal heating circuit does not pass through the current, and the cell is charged and discharged normally;
When the temperature is low, the internal heating circuit is turned on and the electric core is heated. After heating to the target temperature, the electric core is charged and discharged normally.
The internal schematic diagram and circuit diagram of the cell are as follows:
It can be seen from the heating of the cell measured from the pole ear in the figure that the temperature of the inner and negative ears is lower than that of the charge discharge current switch. When the heating cell is in the on state, the heating flows directly through the heater. The heating nickel foil is not partially from the positive pole. The heating pole switch will cut off the heating nickel foil, and then there is current. The negative pole and the lug are disconnected from the negative pole. At this time, the current will flow through the cell, the three ears of the hot nickel foil of the cell are outside the cell, and the circuit is as shown in Figure 2. When the system can be constructed normally and fully, the switch connection is added, as shown in:
Cell discharge detected. As shown in the figure, the hot nickel foil is connected with the. When the system temperature is high, III: thermal inspection
This internal heating cell completes the temperature rise in a short time and only loses a small part of energy:
At present, this kind of cell is in the trial production stage. How to further improve the heating efficiency and reduce the weight of the heating mechanism is very important
The next main research direction.
Conclusion:
To match the requirement of cold countries where you need reliable energy storage solution in outdoor application,
EverExceed research and development engineers were working for long time for a suitable solution and thus came the new technology. So for your cold temperature
energy storage solution choose EverExceed as your brand with complete reliability.
