Inverter fusing

[headlight]

I am hoping to fit my new inverter this weekend.
I will be fitting a 200 amp Mega fuse on the battery end of the 12v positive feed cable.
Do I also need to fuse the negative 12v feed as well ?

 

[Gizmouk]

No fuse required on neg cable.
Make sure you size the cable correctly. If not sure post the cable run (length), and size of inverter so either I or other can do the calcs.

 

[headlight]

No fuse required on neg cable.
Make sure you size the cable correctly. If not sure post the cable run (length), and size of inverter so either I or other can do the calcs.

Thanks for that, just wanted clarification.
I've already been advised on here, 2,000 watt inverter, 60cm cable lengths, 35mm2 cable 240 amps and 200 amp fuse.

 

[dawsey]

Be careful with fuses on the positive feed line to inverters. Ask yourself what you want to protect.

All invertors will have their own internal low voltage fuse or more advanced protection, so you aren’t protecting the invertor. It is the wire run and the battery itself, thus another protection is to make sure the run is as short, high CSA and mechanically well protected as it can be. A short on the negative will be protected by the invertors internal protection.

Remember the 12V DC feed line to an invertor is going to be carrying very heavy current - which will be sustained if you are using lithium batteries and things like air fryers or other heavy draws. Any fuse by its nature is a point of increased resistance. So are the terminations either side of the fuse holder, and the fuse to fuse holder electrical connection. That’s four additional small summed resistances and one big one (the fuse itself) If you don’t design and size correctly it will regularly get hot in continuous use, and then maybe start to thermally degrade. This was why there never used to be a fuse on the lead from battery to starter motor on cars.

I used to use an inline 150A then a 180A full size MIDI fuse in the cabling from my lithiums to my 2000W invertor. No matter how big I made the cables (50mm CSA) - I could not stop the fuse assembly getting very hot when the air fryer was being used (125A continuous). For that reason I removed it. The cable is now direct and stays cool.

For this reason many would advise no additional fuse between invertor and battery. The invertor protection is sufficient. To protect the cables, use the shortest (max 0.5m) and largest CSA and most mechanically protected (dual sleeves) cables you can, and avoid passing big DC cables through high risk metal bulkheads etc

 

[Lenny HB]

I used to use an inline 150A then a 180A full size MIDI fuse in the cabling from my lithiums to my 2000W invertor. No matter how big I made the cables (50mm CSA) - I could not stop the fuse assembly getting very hot when the air fryer was being used (125A continuous). For that reason I removed it. The cable is now direct and stays cool.

Probably down to a poor quality fuseholder.

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[scotjimland]

Probably down to a poor quality fuseholder.

exactly...

the fuse is to protect the cable,,, not the inverter . and should be rated for max current of the cable

negative does not require a fuse

 

[Ray-Vic]

At college many, many moons ago we were taught that fusing should be the nearest fuse to 115% of the circuit maximum current and less than the current rating of the cable. There are, of course, different types of fuses with the same ratings, such as motor rated fuses and time delayed fuses etc so making sure the correct type of fuse is being used is as important as the rating (same goes for trips).