question

The table you show covers the range of the Orion Tr smart products, from 10A to 30A. I agree with your gut feeling as to which fuse values to advise.

No, they are not to high. The fuses is there to protect the cable, in case of a short, not the Orion.

The fuses also has to be as close to the batterys as posible.

If there was no fuses and a short happen, the cable could catch fire.

hello, I have a very similar question. for a 12/12-18A, the specified fuse/breaker is 60amps. If the unit runs at 18-25amps, with a short circuit current of 40amps, isn't a 60amp fuse too large?

I understand that the purpose of fuses is to protect the wires, but for this installation i am using 4awg wire (to minimize voltage drop)from the engine to the rear of the vehicle, and then i am using a post to step back down to a 6awg to the Victron.

I agree with them being over rated fuses. Yes we in theory we design fuses to cable ratting but in practice we do not. For example a 1.5mm cable rated at 16 amps (enclosed) we fuse at 6 amps on lighting. I have cables designed to take 1000's amps but running on 700 amps fuses. If you have a 100 Ah battery with 60 amp midi fuse at a short circuit current of 100 amps it will take around 300 second to melt according to the Time-current curves. This device is deigned to charge at 30 amp so why would you not put in a 40 amp fuse. It will still protect the cable and lower the time in short circuit to 3 second. I've worked as a electrical engineer for many years and never seen fuses fitted to cable design. Most are fitted to design current plus the % working temperature. So 30 Amp design current at 25 deg will require a 37.5 amp fuse, closes to this will be 40 amp.