Lithium rechargeable batteries are made from lithium-ion (li-ion) cells, the core component of the battery. The size and makeup of the battery is determined by the equipment it powers; a mobile phone will use a small single cell, an electric vehicle will use thousands of cells.
Single cell
Custom battery pack comprised of many cells
The chemical energy stored in lithium-ion cells is considerably more dense than in previous cell chemistries. The materials used to make the cells are highly reactive and must be safely contained and managed to ensure safe working operation throughout their life.
Lithium-ion cells can be damaged through overcharging or over-discharging. Extending the life and performance of each cell relies on ensuring that it operates within optimum safe limits. Besides just being inefficient, an overcharged li-ion cell presents a combustion hazard, and that puts more than just your battery pack at risk.
Why do lithium-ion cells need to be handled carefully?
Risk of combustion or rapid disassembly occurs when a cell is subjected to abusive conditions, perhaps due to the voltage exceeding its safety limits, drawing too much current, or a short circuit.
Metallic particles within the cell also introduce a risk of overheating, and reputable manufacturers work hard to eliminate impurities entering the construction process. As thermal instability starts in one cell and may then transfer to adjacent cells, a battery pack can create a serious hazard for several minutes, or even hours.
Lithium-ion cells have sometimes gained an unsafe reputation due to a number of inferior-standard cell suppliers and manufacturers. When manufactured by a reputable company, these cells are generally safe under the conditions which they have been designed for. Li-ion cells are assembled with specialist tools and components into a battery pack leveraging their advantage over other chemistries in smaller size and weight to high power ratio (known as Low-SWaP).
How can I reduce risk and optimise efficiency?
Because it’s possible to overcharge one cell within a battery to unsafe voltage levels before the battery registers as fully charged, cell voltage monitoring is essential.
That is where a battery management system (BMS) comes in. A BMS is an electronic circuit which can be fitted to any appropriate battery and, as well as keeping the battery safe, can also supply diagnostic and informational data to the host equipment or even via IoT to cloud-based customer applications.
A good BMS does a lot more than just voltage and current monitoring; while a protection circuit may provide some mitigation against the risk of rapid disassembly, a BMS will actually contribute to the longevity and efficiency of your power pack.
What’s special about our BMS?
Steatite designs in-house, custom BMS which monitor and manage the voltage, current and temperature of li-ion batteries. Cell and cell string level monitoring ensures all cells are performing equally and the BMS balances cell string voltages when this is required, extending the lifecycle and performance of the battery. The BMS may do other ancillary functions such as controlling a charger, switching contactors or turning a cooling fan on and off.
Output data is transmitted via I2C Comms data (suitable for small packs) or CAN bus protocols (best for larger packs) or other protocols to suit the application (Modbus, SMbus, SPI, Serial etc.). These bus types allow the attached equipment to access real-time monitoring and performance on the battery pack applications.
State of Health data shows the degradation level of the overall battery, alerting users to maintenance requirements and maximising the life of the battery.
State of Charge data indicates how much charge is left within the battery pack so users can efficiently plan the next charging cycle.
Our latest addition to the BMS family is specifically for 40-60v batteries and is due to manage the power for delivery drones, electric delivery vehicles, mobile welding machines and similar.
Each BMS is specifically configured for a particular use, making each system optimal for its own application. A change of usage for the battery has to be communicated as it might alter the condition of the power pack. Our battery experts can assist with these customisations.
What about transporting lithium batteries?
Transportation rules are highly governed and our team will guide you through the process to meet all legal and industry safety standards. Lithium battery transportation is subject to international regulations which differ depending on the mode of transportation; whether air, sea or road.
For example, in 2016, regulations banned the transportation of bulk shipments of li-ion batteries on passenger aircraft and introduced guidelines around packing and labelling the shipment.
All new lithium battery packs must undergo a series of rigorous tests which are designed to simulate the effects of transportation. You can read more details on our Lithium Battery Transportation page. The transportation of lithium batteries is complex, but at Steatite we have the expertise to guide you with managing this.
We regularly help our customers by advising on required certifications to enable batteries to be transported both nationally and internationally, and to achieve compliance with higher standards for specific market sectors, CE or UKCA marking and so forth.
We will manage the entire process of getting your custom battery design tested and certified ready for use with your equipment.
Get in touch to understand more about our custom Battery Management Systems and how we can help deliver safer power to your equipment for longer.
