Battery, motor and electric control technology are the most core technologies of electric vehicles. Because the use of these three technologies, every electric vehicle needs and directly affect the vehicle range, acceleration time and other parameters. The most core function of the electric control is the battery management system (Battery management system) or BMS for short.
The three electric technologies on electric vehicles: battery, motor and electric control technology are the most core technologies of electric vehicles. Because of the use of these three technologies, every electric vehicle needs and directly affects the vehicle's range, acceleration time and other parameters.
These three technologies are the barrel of the electric car, any one of them has a short board will directly affect the performance of the vehicle.
Among the three electric technologies, the battery and motor have a more obvious impact on the performance of electric vehicles. For example, the power of the motor directly affects the power performance of the vehicle, while the amount of energy storage of the battery of a pure electric vehicle is closely related to the range of the vehicle.
But what is the specific technical application of the electric control technology in the electric vehicle, which is the same as the three electric systems? Why can it occupy a place in the three electric systems along with the battery and motor?
The core function of the electric control is the battery management system (Battery management system) or BMS for short.
Without this system, the charging and discharging of the power battery and its service life will be greatly reduced. If the battery is compared to a team of soldiers in the war, the BMS system is the staff of this group of soldiers plus the general, so that the electric vehicle in the practical application of the effect of half the effort.
Why do we need BMS system?
The BMS system is mainly used in the secondary battery, especially for the current mainstream use of lithium-ion battery electric new energy vehicles is particularly important.
No matter what kind of lithium-ion battery the vehicle uses, the power battery is made up of a small battery monomer through the series, parallel connection of the battery pack, and then the battery pack finally composed of the vehicle's power battery unit.
And in the battery pack really play a role in energy storage is the battery pack in each small battery monomer, such as Tesla use of 18650 lithium-ion battery, in fact, the number represents that each battery monomer diameter of 18mm, length of 65mm.
And the battery pack of an 85kW?h version of the Tesla Model S is made up of close to 7000 18650 lithium batteries.
With so many cells in a car, each small cell is manufactured separately, and because of the battery's electrochemical properties, the factory battery has a problem with the consistency of each cell's energy storage.
And charging from a charging port to charge the car, how to ensure that each piece of battery is fully charged, but not because of overcharging damage to the battery is one of the problems to be solved by the BMS system.
How does the BMS system manage so many battery cells?
Typically, BMS systems go through two parts to determine how to manage the battery pack, which are the detection module and the primary acid control module.
Tesla's battery management module
The implementation of the detection module is relatively simple, mainly through sensors to collect information on the parameters of the battery in use such as: temperature, elegance and current of each battery cell, elegance and current of the battery pack, etc..
These data play a vital role in the subsequent battery pack management, and it can be said that without the support of these battery status data, the system management of the battery can not be discussed.
According to the collected data, the BMS system will assign how to charge the battery according to the actual situation of each battery unit, which battery unit has been fully charged can stop charging it, etc..
And in the process of use, the state of each battery is determined through state estimation, and the reasonable utilization of the battery is achieved through SOC (State Of Charge), SOP (State Of Power), SOH (State of Health), as well as equalization and thermal management.
Electric vehicle BMS seven failure analysis method.
1、Observation method When communication interruption or control abnormality occurs in the system, observe whether there are alarms in each module of the system and whether there are alarm icons on the display, and then investigate one by one for the derived phenomena.
2、Fault recurrence method vehicles in different conditions of the failure is different, in the conditions allow, as far as possible in the same conditions to let the fault recurrence, the problem point to confirm.
3、Exclusion method when the system occurs similar interference phenomenon, should remove each part of the system one by one, to determine which part of the system is affected.
4、Replacement method When a module appears abnormal temperature, voltage, control, etc., swap the same number of series of module positions to diagnose is a module problem or wiring harness problems.
5、Environmental inspection method When the system failure, such as the system can not be displayed, we first do not rush to in-depth consideration, because often we will ignore some details of the problem. First we should look at the obvious things: such as whether the power is on? Has the switch been turned on? Is not all the wiring is connected? Perhaps the root cause of the problem is in it.
6、Program upgrade method when the new program burned after an unknown fault, resulting in abnormal system control, you can burn the previous version of the program for comparison, to analyze and deal with the fault.
7, data analysis method when the BMS control or related failure, the BMS stored data can be analyzed, the content of the message in the CAN bus analysis
