Safe of electric scooter —— BMS and Charger

Safe of electric scooter —— BMS and Charger

Battery Management System (BMS) is an important line of defense for battery safety. This is an electronic circuit containing a chip, also known as a battery protection line or protection board. The BMS leads are connected to the battery leads to manage the battery. Electric cars are usually installed at the end of a set of batteries and are encapsulated outside. BMS has a triple effect: first, it monitors the voltage, current size and battery pack temperature when each battery is charged and discharged, Ma explained. When a battery is fully charged, BMS adjusts the current to pass through the bypass, discharge, a battery unit voltage is too low, through adjustment to make each battery unit discharge voltage balance. Furthermore, when a problem with the battery pack is detected, the charging current is cut off. BMS is only possible in lithium batteries, which are not equipped with BMS because they are not easy to explode.

Xue Yu said that although there is no mandatory regulation, but for safety reasons, lithium batteries are equipped with BMS. In reality, the price of e-bike BMS is different, cheap a few dollars, expensive a dozen yuan to twenty or thirty dollars. Correspondingly, the function and reliability of electric vehicle BMS are also different. Poor BMS may be a shoddy, with no effect.

In contrast, the BMS of electric vehicles can manage thousands of batteries more precisely, and its cost has increased significantly, at a price of 230,000 yuan. Xue Yu said that electric vehicle lithium battery factory, there are original supporting BMS, if the battery changed to high voltage, high capacity, it may be replaced BMS and battery does not match, does not play a protective role. For ebikes, a dozen dollars of BMS has been able to play an effective role in protection, technically no difficulty, just the cost of the problem.

Chargers are also an important part. Around 2016, a 22-year old migrant girl from Beijing brought home lead-acid batteries from a Superpower electric car to charge. In the middle of the night, the charger was too hot for the battery, a short circuit occurred, and after the fire, the girl was burned to death. Chargers producer Yogi Chaowei was indicted to court, Ma Guilong as an expert witness in court. In previous years, Ma Guilong has been involved in the "electric bicycle charger technical requirements" in the preparation of national standards, in the discussion, he urged electric vehicle lead-acid battery charger manufacturers to increase the function of charger to prevent heat out of control. This will increase the cost of manufacturers by a few yuan, once opposed by individual manufacturers, but ultimately in everyone's efforts, can be adopted, the relevant provisions are written into the document.

However, "Electric bicycle charger technical requirements" GB/T 36944 is the recommended standard. Ye Zhentao said that after the release of this standard, only a few enterprises to implement, in 2020 Jiangsu Province Market Supervision Authority spot check 50 batches of chargers, only 2 to implement this recommended national standard; Due to the insufficient recommended national standards, the State Standards Committee of the State Administration of Market Supervision and Administration has set up a mandatory national standard for chargers, which Xue Yu is responsible for drafting. On the afternoon of September 28, the mandatory national standard was validated and is expected to be issued by the end of this year or early next year.

The most important thing for lithium battery chargers is to establish an open protocol between BMS and chargers to communicate between the two, ' Mr. Ma said. BMS is the equivalent of an "intermediary" between a lithium battery and a charger. Just as doctors prescribe drugs to patients, BMS monitors the battery and tells the charger what to do with it. Once the battery temperature is found to be too high, the charger should stop charging immediately. The lithium battery pack should be equipped with a temperature sensor for BMS monitoring. This is the only way to solve the lithium battery combustion at present, should be included in the mandatory national standard. And the market so-called a brand of batteries must match a manufacturer charger, in fact, is only a bundle of commercial interests.

Domestic electric two-wheeler (including light motorcycle, electric motorcycle, ultra-standard electric vehicles) lead-acid battery charger manufacturers show a clear concentration of production enterprises and regions. The primary market is the annual sales volume of the vehicle factory charger 25 million, of which Nanjing Xipu, Nanjing Tenor, Zhejiang Juyuan three accounted for 70% of them. Take 48V, 20AH specification charger as an example, the primary market charger cost about 25 yuan. The secondary market is mainly occupied by more than 70 enterprises in Qinban Town, Tianzhou City, Anhui Province, with a market share of 70% of the secondary market, the quality of chargers is lower than that of the primary market, with annual sales of about 100 million, and the cost of a charger is 18 yuan. Lithium battery chargers are mainly in Wuxi Sans, Shenzhen Fuyuandian and other manufacturers. Compared with lead-acid battery chargers, lithium battery charger market is still in its infancy, there are no large enterprises, many small factories still have a lot of production irregularities.