Sosaley is redesigning its BMS Master Controller to be used as an Automotive Battery Management System (autoBMS). The proposed configuration of autoBMS will have the following major features:
- Easy plug-in and plug-out into the battery terminal block of the e-vehicle.
- Can handle cell blocks that are detachable.
- Communicate through the CAN bus.
- Have a touch screen for displaying data. The screen size could be 4 to 7 inches in size.
- Monitor and manage each cell individually. There could be a limitation on the maximum number of cells. This can be specified later.
- Manage up to 150Ah of current and roughly 200 volts.
The autoBMS will be in the form of a plug and play device. A terminal block will be fixed permanently on the vehicle. The terminal block will be hardwired to each battery cell. The autoBMS block can be simply plugged into the terminal block. It will get both data and power from the terminal block.
Internally, the autoBMS will multiplex the analogue signals, do an ADC conversion and read the data that is coming from each cell. In addition, it will read the status of all the cells through a separate connection in the terminal block.
When we look at a BMS for the EV industry, we are looking far beyond the BMS that uses lead-acid batteries. The following functionalities are considered essential:
- Protect the cells from damage
- Prolong the life of the cells
- Ensure that the cells meet certain minimal functional requirements
- Interact with vehicle management
- Predict emergency situations so that they can be avoided
autoBMS Block Diagram
Main Functional Units
Essentially, Sosaley’s autoBMS will have three functional units
- Battery Monitoring Unit
- Battery Control Unit
- Battery Communication Unit
The battery monitoring unit will read and display the SOC and calculated SOH of the cells. The battery control unit will interact with the engine ECU and manage the charger output. The communication unit will link autoBMS to the Engine ECU, displays, instrument clusters and other external devices.
All communication between the autoBMS, the vehicle, it’s own display and any other device will be only through the CAN bus. The autoBMS will need a lot of data from the vehicle management system including distance driven, data from internal sensors such as air conditioning, tyres, etc. These will be used to calculate the energy levels of the battery and how much is left.
Broad Feature List
|SOC||State of Charge represents the short term capability of the cell or cell bank.|
|SOH||The State of Health is an estimate of the life left in the cell. This is calculated based on the latest readings and the parameters compared with information of a brand new cell that is stored.|
|History||The autoBMS will store all data read with date and time stamp. This can be used by the service teams.|
|Communication||autoBMS will use the CAN bus to drive the on-board display as well as an interface to the automotive ECU.|
|Monitoring||The autoBMS will monitor 5 parameters of each cell – voltage, current, temperature, impedance, and chemical composition.|
|Display / Alarms||The autoBMS will support setting of alert parameters and issue a warning when these thresholds are crossed.|
|Charge Control||With historical and current information on each cell, the autoBMS will decide the amount of current that can be used to charge each cell.|
|Demand Management||The autoBMS system can have a set of load priorities and instruct the vehicle management system to cut down loads when the battery comes to needing a charge.|
|Cell Protection||The autoBMS will take appropriate action when needed by interacting with Engine ECU to protect the cells.|
|Fail Safe||The autoBMS will use sleep mode and internal power to save data.|
|Cell Balancing||The autoBMS will use ageing and current conditions of the cells to ensure individual cells are not stressed.|
|Limp Back Home||The autoBMS can provide information to the driver to ensure he has enough energy to reach home or the nearest charging station.|