patrickj avatar image
patrickj asked

Orion TR Smart 12/12-18a fuse and wire gauge chart

Is there a fuse amperage and cable gauge/length table for the Orion TR Smart 12/12 18 isolated charger?

The online manual lists fuse amperages for input and output batteries and cable gauges for various lengths, but the suggested fuse is 60 amps at both the input and output batteries. That seems rather excessive for a charger outputting 18 amps.

I definitely can't let the charger try to pull that kind of amperage on my installed cables which are presently fused at 30a.

orion-tr smartfuses
2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

2 Answers
Alexandra avatar image
Alexandra answered ·


The fusing says max 60A. This is because the max sized cable that can be installed there is 16mm².

And the size fuse you install would generally be related to the gauge wire installed.

A fuse should not blow in normal operation and is really not related to normal operation, neither is it there to protect the device (it has its own onternal protections). It is there to prevent a fire in the wiring.

2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

patrickj avatar image patrickj commented ·

Thanks Alexandra. My electrical knowledge is pretty basic.

However, I do understand the fuse is there to protect the wire. But it also seems that maximum spec for wire gauge and fuse in that table is meant to accommodate the power consumption of the 12/12 40A rather than the 12/12 18A. That is, the 12/12 18A won't be drawing anywhere near 60A.

I guess the question I should have asked is what is the *minimum* fuse amperage and wire gauge required for the 12/12 18A to operate normally?

I presently have about 30 feet of 10 awg cable protected by a 30A fuse running from the starter battery in my car to the battery compartment in my trailer. Will the 12/12 18A be blowing that fuse (or overheating the cable) under normal operation?

0 Likes 0 ·
Alexandra avatar image Alexandra ♦ patrickj commented ·


The battery is a fairly large current source again the fuse has nothing to do with the orion. Place it close there, it will blow. The fuse blowing is to disconnect the large current source (battery) from the wire.

The maximum wire size statement is really about max terminal size. And the length you run determines gauge of wire. So if you have it close by the battery you can gauge down. Further.... Larger gauge to the max of 16mm²

2 Likes 2 ·
Alexandra avatar image Alexandra ♦ Alexandra ♦ commented ·


Sorry i did not get back to you.

In theory a 10awg will blow a 30A fuse but also might not on heat, it depends on the fuse. A thermal blow is different to an overcurrent blow.

The minimum is difficult to answer directly as there are quite a few different fuse types. You would need to know do you have a fast blow fuse or a slow blow?

I guess this would also apply to @Peachumz.

There are also local regulations and a few other considerations, so being ultra specific is not entirely possible in a manual. You do have to some extent do your own research on the components you choose and use. As @kevgermany mentioned.

1 Like 1 ·
patrickj avatar image patrickj Alexandra ♦ commented ·
No worries on the delay on your response. And thank you for it.
0 Likes 0 ·
peachumz avatar image
peachumz answered ·

I have the same charger, the same question, and the same confusion over the information being provided.

As far as I can see, the version of the online manual doesn’t say max, it just says 60A. It probably should say max, because surely the minimum 0.5m 6mm2 cable run would melt under 60A.

I think the cable run ranges are due to voltage drop as mine is 4 meters and I need 16mm to get under 3%. So my cable can take well over 60A, but should never have anywhere near that running down it.

The manual has specifications for the 12/12/18 that says:

continual output = 18yA(as per the model name)

maximum output for 10 seconds = 25A

short circuit output = 45A

So 45A seems to be the max fuse size for this model (and perhaps even less if rating at 25*1.25=32A) and then scale down depending on the wiring to protect that.

I would suggest that Victron are putting out a generic all model covering manual that’s not going to get too prescriptive in areas of variability for self preservation reasons; and so they provide their wiring manual to try and help customera with installation decisions.

I’m not an electrician (in the interests of covering myself) and this is my “intellectual” surmise, but I would love to hear some professional/Victron feedback on this to help give closure to us amateur builders.

1 comment
2 |3000

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

kevgermany avatar image kevgermany ♦♦ commented ·
Fuse for cable size as a maximum.

Fuse for max current as you see fit.

Also remember that with common fuse types, there is some latitude for small/short over current times. And that cheap fuses may not perform to specifications.

2 Likes 2 ·