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Electronics Engineering QUESTION #11720
Question 1
The purpose of a pre-charge circuit in a battery management system (BMS) for a Li-ion pack is to:
  • Equalise cell voltages before main charging begins
  • Limit inrush current to capacitive loads at initial power-up
  • Trickle charge deeply discharged cells below 2.5 V before full CC charge✔️
  • Balance cells using a passive resistor network
Correct Answer Explanation
Pre-charge in Li-ion BMS applies a low current (typically C/10 or less) to deeply discharged cells with voltage below ~2.5–3.0 V per cell. Charging a deeply discharged Li-ion cell at full CC current can cause lithium plating, internal short circuits, and thermal runaway. Pre-charge safely recovers the cell to a safe voltage before commencing full CC charging.