Battery Management Systems
Many new battery technologies, such as Li Ion, Li nano-phospate, Lithium ferro-phosphate, require accurate, reliable means of both protection and data reporting. A BMS or Battery Management System is the on-board electronic method of achieving these aims. I2C communication is the standard method of communicating with the BMS in a battery pack, and Creasefield has developed custom ATE and programming software utilising this to automatically test and program the battery packs during and post-production.
A full BMS will include the following abilities:
Protection
The BMS protects batteries, and users, from harmful effects if the battery begins to deviate from its Safe Area of Operation (SAO), caused by:
- Overcharging
- Overdischarging – particularly dangerous for Lithium technologies
- Pack temperature outside safe limits
- Overcurrent being applied
- Pack short-circuit
The BMS protection circuits will disable (either permanently or for the duration of the fault) the pack output or charging input and render the pack safe.
Monitoring
In order for the BMS to determine if the pack it operating outside of its SAO, many variables of the pack are monitored, such as:
- Voltage – both pack and individual cells
- Current – monitored during charge and discharge, as well as the drain current of the BMS
- Temperature – cell and pack
- State of charge – calculated differently by different BMS IC’s (impedance tracking, learn cycle etc.)
Computation and Optimisation
The pack monitoring carried out by the BMS allows for the long-term computation of usage statistics, such as:
- Peak values of voltage, current, temperature etc
- Lifetime energy discharged
- Lifetime energy charged
- Number of pack cycles
These are particularly useful for fault finding of products and future development work.
The BMS monitors and balances individual cell voltages in order to:
- Maximise battery capacity, and
- Prevent localised charging/discharging of the cells, which also helps to prolong battery life
Communication
The BMS incorporates 2-way communication (usually via I2C) between the battery pack and host application, test equipment or development environment. This means:
- Monitored values can be reported instantly to the host application – showing the remaining capacity or warning of any safety flags set.
- Remote programming of battery parameters can be achieved – allowing changes to pack operation can be implemented after the product has been in use
- Reliable, accurate and tailored ATE - designed to communicate with the battery pack during testing to ensure that every pack and BMS manufactured conforms to the highest parameters
- Individual pack-specific information, such as serial number, batch code etc, can be stored automatically within the BMS memory, allowing for easy pack tracking.
Our expertise and in-depth knowledge of battery technology, electronic systems and testing techniques mean Creasefield delivers quality products designed and tested to the highest standards each and every time.