About the Norwegian provider of Electric Vehicle battery webpage EVlithium.net
Evlithium.net Is the developer of the norwegian evlithium BMS system. Wee are continually working on the system for better improvements for you and your electric vehicle.
Automotive battery management is much more demanding than other battery management systems. It has to interface with a number of other on board systems, it has to work in real time in rapidly changing charging and discharging conditions
as the vehicle accelerates and brakes, and it has to work in a harsh and uncontrolled environment. This example describes a complex system as an illustration of what is possible, however not all applications will require all the functions shown here.
The functions of a BMS suitable for a electric vehicle are as follows:
Monitoring the conditions of individual cells which make up the battery
Maintaining all the cells within their operating limits
Protecting the cells from out of tolerance conditions
Providing a "Fail Safe" mechanism in case of uncontrolled conditions, loss of communications or abuse
Isolating the battery in cases of emergency
Compensating for any imbalances in cell parameters within the battery chain
Setting the battery operating point to allow regenerative braking charges to be absorbed without overcharging the battery.
Providing information on the State of Charge (SOC) of the battery. This function is often referred to as the "Fuel Gauge" or "Gas Gauge "
Providing information on the State of Health (SOH) of the battery. This measurement gives an indication of the condition of a used battery relative to a new battery.
Providing information for driver displays and alarms
Predicting the range possible with the remaining charge in the battery (Only EVs require this)
Accepting and implementing control instructions from related vehicle systems
Providing the optimum charging algorithm for charging the cells
Providing pre-charging to allow load impedance testing before switch on and two stage charging to limit inrush currents
Providing means of access for charging individual cells
Responding to changes in the vehicle operating mode
Recording battery usage and abuse. (The frequency, magnitude and duration of out of tolerance conditions) Known as the Log Book function
Emergency "Limp Home Mode" in case of cell failure.
In practical systems the BMS can thus incorporate more vehicle functions than simply managing the battery. It can determine the vehicle's desired operating mode, whether it is accelerating, braking, idling or stopped, and implement the associated electrical power management actions.
One of the prime functions of the Battery Management System is to provide the necessary monitoring and control to protect the cells from out of tolerance ambient or operating conditions. This is of particular importance in automotive applications because of the harsh working environment. As well as individual cell protection the automotive system must be designed to respond to external fault conditions by isolating the battery as well as addressing the cause of the fault. For example cooling fans can be turned on if the battery overheats. If the overheating becomes excessive then the battery can be disconnected.
Protection methods are discussed in detail in the section on Protection.
Battery State of Charge (SOC)
Determining the State of Charge (SOC) of the battery is the second major function of the BMS. The SOC is needed not just for providing the Fuel Gauge indication. The BMS monitors and calculates the SOC of each individual cell in the battery to check for uniform charge in all of the cells in order to verify that individual cells do not become over stressed.
The SOC indication is also used to determine the end of the charging and discharging cycles. Over-charging and over-discharging are two of the prime causes of battery failure and the BMS must maintain the cells within the desired DOD operating limits.