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.