Midi Fuses

MIDI fuses are blade-type fuses for direct current in the 30 to 200 A range. They are the intermediate size between small vehicle fuses and high-current ANL fuses, and are the most commonly used type for protecting individual circuits in an installation: the solar regulator, the booster, the charger or the service distribution panel.

Where does a MIDI fuse go?
Every cable coming out of the battery or the busbar A circuit leading to a piece of equipment requires its own protection, rated for that specific cable. That’s where the MIDI comes in: for circuits ranging from 30 to 200 A, which make up the majority in a motorhome or boat installation.
The main cable to the inverter, which may draw 200 A or more, is normally protected by a ANL fuse o MEGA.

How to choose the amperage
The rule is that the fuse protects the cable, not the appliance. It should be selected to be higher than the appliance’s maximum operating current and lower than the current rating of the cable you have installed.
Common examples: a MPPT controller A 30 A circuit is protected by a 40–50 A MIDI; a DC-DC booster 50 A, with one rated at 60–80 A.
If the fuse blows as it should, it isn’t because it’s too small: it’s because something is drawing more current than anticipated. Increasing the amperage without investigating the cause is tantamount to trading one safety measure for a fire hazard.

DC fuse, not AC
A fuse designed for alternating current utilises the waveform’s natural zero-crossing to extinguish the arc. In direct current, there is no zero-crossing, so the arc may persist and the fuse may fail to interrupt the fault. All the MIDI units we supply are approved for direct current.
You’ll also need their fuse holder the correct one, and a cable of the appropriate cross-section — check this in the Cross-section table by power rating.
Tell us which appliances you’re going to protect and which cable you’ll be using, and we’ll tell you the exact amperage for each fuse: free advice.