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Can I use a Circuit Breaker instead of a MIDI Fuse?

This information is applicable to the following product ranges: 

  • BCDC In-Vehicle Battery Chargers
  • Battery Management Systems
  • Smart Battery Isolators
  • Pure Sine Wave Inverters

This is a common question for customers installing our charging products, particularly when installing our BCDC In-Vehicle Battery Chargers, Battery Management Systems, Smart Battery Isolators and Inverters. While many would like to use circuit breakers, as these can be reset easily rather than having to replace a fuse, there are some important considerations when using them in high-current situations. 

PROS AND CONS OF USING A CIRCUIT BREAKER

PROS

  • Can be easily reset without needing replacement 
  • Clear visual indication when they have tripped 
  • Simple installation

CONS

  • Prone to premature tripping under high current due to internal heat build-up (see hot circuit breaker pictured below)
  • Can only handle about 90% of their rated current (e.g. a 50A breaker will handle 45A before tripping) 
  • Larger size compared to MIDI fuses 

This diagram was created using a thermal imaging camera which visually shows the heat build-up in the circuit breaker.

In circumstances like this, they are only able to handle up to 80-90% of their rated current resulting in tripping prematurely under the circuit breaker’s max current rating.

WHY DO WE RECOMMEND USING A MIDI FUSE?

MIDI fuses provide more reliable protection for high-current applications and avoid many of the issues that circuit breakers face under heavy load.

PROS AND CONS OF USING A MIDI FUSE

PROS

  • Compact size, allowing multiple fuses to fit in the space of one circuit breaker

  • Easy visual identification when blows

  • Less susceptible to heat build-up

CONS

  • Must be replaced once blows

  • Spare fuses need to be available for quick replacement

If you prioritise long-term reliability, particularly in high-demand installations like inverters and charging systems, we recommend using MIDI fuses.