MEGA Fuses

MEGA fuses are high-breaking-capacity ceramic fuses designed to protect high-current DC circuits: the connection between the battery bank and the inverter, the main distribution board or the alternator. They are the standard choice for 12, 24 and 48 V installations.

Why a MEGA and not a conventional fuse?

By the short-circuit current that a battery can supply. A 48 V lithium battery pack can deliver several thousand amperes during a short circuit, and a standard fuse will not cut it off: it vaporises and allows the arc to continue. The MEGA is constructed with a ceramic body and a quartz sand filling, which absorbs the arc’s energy and extinguishes it.

Our MEGA from Victron They are rated at 80 V DC, with sufficient cutting capacity for 12–48 V power supplies.

Which MEGA fuse rating should I choose?

Above the maximum continuous current that will flow, and below the cable’s capacity. The current is determined by the inverter: a 5000 VA MultiPlus inverter operating at 48 V may draw around 125 A continuously and considerably more at peak, so the fuse should be selected with a margin above the continuous current but without exceeding the cable’s capacity.

Available from 100 A to 500 A. If the fuse blows whilst the inverter is operating within its range, the problem is not the fuse: it is either incorrectly sized or the cable is too short.

Where is the battery fuse located?

As close as possible to the positive battery terminal, ideally in the fuse holder itself, which is bolted to the post. The reason is that the section of cable between the battery and the fuse is unprotected, and if it rubs against the chassis, there is nothing to cut the circuit.

See also the string fuses and the terminals required for assembly.