Overcurrent protection

Example

Use in Lemonergy

Make series/parallel architecture explicit.

This is a reference concept. No executable Lemonergy block has been verified for this term.

Connected concepts

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Current sensor

The device that measures pack current for coulomb counting and protection: a precision shunt resistor read by an amplifier, or a Hall-effect sensor around the cable. Offset error in this sensor is what makes SOC drift between OCV corrections.

Fuse

A link that melts and opens the circuit when current exceeds its rating. Packs use a main fuse in the high-voltage path and often a small fuse on each parallel cell connection, so one shorted cell does not drain its neighbours into the fault.

MOSFET

A transistor switched by the voltage on its gate, with an on-resistance of milliohms or less in power parts. Low-voltage packs use back-to-back pairs as charge and discharge switches, since each conducts backwards through its body diode; BMS chips use small ones for balancing, and silicon-carbide MOSFETs switch 800 V inverters.

Protection circuit module

The small circuit on a consumer cell or pack that disconnects it on overvoltage, undervoltage, overcurrent or overtemperature, using MOSFETs as switches. It is the minimum BMS; it protects but does not estimate state or balance.

Positive temperature coefficient device

A polymer element in series with a cell whose resistance jumps when it heats, choking an external short-circuit current. It resets as it cools, unlike a fuse, but adds resistance and does not help against internal faults.

External short-circuit test

Connecting a charged cell’s terminals through a resistance of a few milliohms and recording temperature and outcome. The result depends as much on the cell’s own resistance and its protective devices as on its chemistry.

References & further reading

Further reading on this topic

These sources provide broader context; they are not presented as citations for every statement in this entry.

1. Extended Kalman filtering for battery management systems of LiPB-based HEV battery packs: Part 2. Modeling and identification

   Gregory L. Plett · Journal of Power Sources · 2004

   Topic background · Battery charge balance, open-circuit voltage, ohmic loss, polarization dynamics and model identification; parameters require cell-specific data.

2. Getting Started with the BQ76925

   Texas Instruments · 2019

   Topic background · A concrete BMS analog front-end example: cell voltage, current, temperature measurement and MCU integration.