Battery cell manufacturers usually specify maximum continuous charging and discharging current limits, along with peak charging and discharging current limits. Lithium-ion cells have different current limits for charging than for discharging, and both modes can handle higher peak currents, albeit for short time periods. In many cases, further derating may be applied to reside within the SOA safe zone in the interest of promoting further battery lifespan. Figure 1 illustrates a typical lithium-ion cell SOA, and a well-designed BMS will protect the pack by preventing operation outside the manufacturer’s cell ratings. The electrical SOA of any battery cell is bound by current and voltage. Monitoring battery pack current and cell or module voltages is the road to electrical protection.
Battery pack protection management has two key arenas: electrical protection, which implies not allowing the battery to be damaged via usage outside its SOA, and thermal protection, which involves passive and/or active temperature control to maintain or bring the pack into its SOA.Įlectrical Management Protection: Current We’ll discuss how these two features work here. There are many BMS design features, with battery pack protection management and capacity management being two essential features. Certification requirements from various government regulations where costs and penalties are paramount if inadequate functional safety measures are in place.Application of the battery and any safety, lifespan, and warranty concerns.The costs, complexity, and size of the battery pack.The technology design scope and implemented features generally correlate with: The BMS certainly has a challenging job description, and its overall complexity and oversight outreach may span many disciplines such as electrical, digital, control, thermal, and hydraulic.īattery management systems do not have a fixed or unique set of criteria that must be adopted. While they perform superbly, they can be rather unforgiving if operated outside a generally tight safe operating area (SOA), with outcomes ranging from compromising the battery performance to outright dangerous consequences. Lithium-ion rechargeable cells have the highest energy density and are the standard choice for battery packs for many consumer products, from laptops to electric vehicles. Here, the term “battery” implies the entire pack however, the monitoring and control functions are specifically applied to individual cells, or groups of cells called modules in the overall battery pack assembly. Reporting operational status to external devices.Continually optimizing battery performance.Estimating the battery’s operational state.The oversight that a BMS provides usually includes:
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