Currently, lithium battery BMS (Battery Management System) balancing solutions are mainly classified into passive balancing and active balancing. Passive balancing is favored by major BMS manufacturers due to its mature technology and low cost, making it the most widely used balancing method in the market. Active balancing, however, faces limitations in adoption due to its higher complexity and cost, though its application scope is gradually expanding.
Passive Balancing Explained
Imagine a lithium battery pack as a wooden barrel, where each cell represents a stave. Due to manufacturing variations and usage wear, the staves become uneven in length.
• Passive balancing is analogous to sawing all staves down to the length of the shortest one. While straightforward and efficient, this approach reduces the barrel’s overall water-holding capacity (i.e., the battery pack’s usable energy).
• Technical Mechanism:
Passive balancing employs resistor-based discharge to dissipate excess energy from higher-capacity cells as heat. This reduces voltage differences between cells, achieving consistency at the cost of energy loss
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Active Balancing Explained
Using the same barrel analogy:
• Active balancing involves using the sawed-off material to extend shorter staves. Though more complex and less efficient in execution, this method maximizes the barrel’s water capacity.
• Technical Mechanism:
Active balancing transfers energy from higher-energy cells to lower-energy cells via energy storage components (e.g., capacitors, inductors, or transformers). This preserves overall energy while harmonizing cell voltages
