Optocouplers use energy flowing through a
light-emitting diode to energize an isolated
circuit by photovoltaic cells that receive
the emitted light. Using an optocoupler,
a BMS can perform HV isolation
measurements and other diagnostics while
maintaining isolation between HV and LV
circuits, which is essential for the safety of
the pack and the users."
Khaled Elmasri
Senior Power Electronics Engineer, Canoo
Another important component for battery fault
protection is an optocoupler. An optocoupler is an
electronic component used to galvanically isolate
different parts of a system and allow for signal
transmission between them. In the context of a BMS,
optocouplers help isolate low-voltage electronics, like
microcontrollers, from high-voltage electronics, like
cell monitoring units and voltage-measuring resistors
that interface directly with the high-voltage battery.
This isolation is typically achieved via a combination
of a light-emitting diode (LED) and a photodetector.
Signals from one side will be converted by the LED
into light pulses, which are then detected by the
photodetector and drive the electronics on the
other side. This electrical isolation ensures the
safety of components in a BMS, especially in fault
conditions where short circuits or overvoltages could
be catastrophic and potentially result in hazardous
conditions for the user.
Because fault protection is also tied to SOC
and SOH, components like shunt resistors, NTC
thermistors, and HV resistors are also necessary.
C h a p t e r 4 | B a t t e r y F a u l t P r o t e c t i o n
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8 Industry Experts Discuss Battery Management Solutions
