MELF glass encapsulated NTC thermistor researched and developed by EXSENSE Electronics Technology Co., Ltd. adopts advanced semiconductor manufacturing process and independent research and development of processing technology, which can play a role in temperature monitoring and temperature controlling in lithium ion battery.
With the popularity of new energy automobile, lithium ion battery has attracted more and more attention, and the problems encountered in the charging process of lithium ion battery has also become factors that major manufacturers need to consider. The negative graphite of lithium ion is difficult to occur intercalation reaction when lithium ion battery is charged at low temperature (usually below 0℃), which leads to lithium metal deposition on the surface of graphite anode and formation of lithium dendrite. It is easy to puncture the diaphragm, resulting in internal short circuit of the battery and cause swelling, electrolyte leakage, explosion fire and other safety problems. At the same time,it is easy to shorten the cycle life of the battery, so lithium ion battery is forbidden to charge at low temperature. In existing technologies, there are three corresponding methods to solve the problem of lithium ion battery charging at low temperature:
First, physical heating, that is, when the battery is detected at a low temperature, start the heating device and make the heater parts wrapped around the battery heat the battery. When the battery temperature rises to the allowable charging temperature, start charging. This method requires an external power supply at low temperatures and consumes additional power at the same time. Sometimes in order to save external power, take advantage of characteristic of the battery which can discharge at low temperatures, using the battery itself in the discharge process of spontaneous heat to achieve self-heating;
Second, adjust the charging cut-off voltage or charging pulse current through the external management circuit. With a certain frequency of pulse current to charge battery, under the condition that no lithium dendrites are generated in the battery, which can be produced through the charging process of the heating effect of the physical and chemical makes the battery temperature rise, and to ensure that the average amount of charge is not greater than battery charging can bear the power, improving the rechargeable capacity of battery and rechargeable security at low temperature. This kind of charging mode is mainly managed by charging management system, which requires the coordination of management chip and its mathematical model, and the use of more temperature sensors, current/voltage control and management devices and other components, which is complex circuit, high cost;
Third, changing the chemical system of lithium ion battery, including changing the cathode active substance, improving the particle size of active substance, modifying the physical substance, etc., but these improvement methods tend to significantly reduce the specific energy of the battery.
According to the electrochemical characteristics of change of rechargeable capacity of lithium ion battery, it is necessary to find a device with change to control the charging current of lithium ion battery, so as to ensure that lithium ion battery can be recharged in a wider temperature range, especially at low temperature. EXSENSE Electronics introduces a lithium ion battery, which includes glass encapsulated NTC thermistor, charging module, battery pack and current regulation module. The main positive end of the battery pack is connected to the positive pole of the charging module through the current regulation module, and the main negative end of the battery pack is connected to the negative + pole of the charging module; The current regulation module comprises a main temperature switch and a number of current regulation branches connected in parallel with the main temperature switch, the current regulation branch comprises a branch temperature switch and the NTC thermistor connected in series with the branch temperature switch; The main temperature switch and the branch temperature switch in each current regulation branch are closed or disconnected in different temperature ranges respectively; The NTC thermistor in each current regulation branch has different resistance values in different temperature ranges.
The specific charging process of this lithium ion battery is as follows:
When the ambient temperature is normal state, the main temperature switch is turned on, the branch temperature switch of each current regulation branch is turned off, and the charging module charges the battery pack directly;
When the ambient temperature is in low temperature state, the main temperature switch is off, the branch temperature switch of one current regulation branch is turned on, and the branch temperature switch of the other current regulation branches is turned off. The charging module charges the battery pack through the battery regulation branch of one current regulation branch.