Fusing 48 to 12 Orion DC-DC

jameshowison

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I am replacing the system in an RV with a 48v system. I have a Victron 48/12 30amp Orion DC-DC converter. Plan is that 48v Input comes from the busbar, runs through a Midnite DC circuit breaker and into the Orion, 12v leaves and feeds the existing RV 12 volt system.

Victron materials say that the 12/24v units have "Input fuse. On 12V and 24V input models only." And the little manual that comes with it says, "the 12v and 24v input models have an internal fuse (not replaceable). The 48v models do not have this fuse: external fuse required".

I *think* that is talking about fusing the input side, although I'm confused about why one would have a fuse at the end of the wire from the battery (with the internal fuses).

I'm also wondering if I should be fusing the output side, treating it as though it was a 12v battery. If so should I be fusing for the max output (40A) or the short-circuit current (60A). Details on the bottom of the second page, third last column (360W).


The wire run from the Orion to the 12V distribution board will likely be short, like a few feet, but since I haven't located each item yet, it may be up to 15ft (round trip).
 

Rocketman

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I would think you want a fuse by the 12v battery - then your wire to the Dc-dc charger - the wire to your 48v battery then the fuse as it connects to the 48v system.

I think the fuse is for if your wire chafes and shorts you want the fuses to pop so you don’t have a run-away short.
 

jameshowison

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I would think you want a fuse by the 12v battery - then your wire to the Dc-dc charger - the wire to your 48v battery then the fuse as it connects to the 48v system.

I think the fuse is for if your wire chafes and shorts you want the fuses to pop so you don’t have a run-away short.

Thanks. I wasn't intending to have a 12v battery, just connect the DC-DC converter directly to the 12v distribution panel. So power would only ever flow from the 48v batteries through the Orion to the 12v distribution panel. Does that change things?
 

Rocketman

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Ok I was thinking a dc-dc charger. For what you have just a fuse by the 48v battery.
 

rmaddy

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You should have a fuse between the bus bars and the Orion DC-DC converter. The fuse must be rated to handle the near 58V of your 48V system (as your other fuses/breakers must as well).

BTW - I don't see a 48V->12V converter that outputs 30A. I just see a single 48V->12V converter that outputs 9A.
 

Abodyofscience

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Fuses with clearing times designed to protect semiconductors are rare.

Ask how much $ for two of their internal non-replaceable fuses.

Protecting wire insulation with a 50 year life is much easier.
 

jameshowison

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You should have a fuse between the bus bars and the Orion DC-DC converter. The fuse must be rated to handle the near 58V of your 48V system (as your other fuses/breakers must as well).

BTW - I don't see a 48V->12V converter that outputs 30A. I just see a single 48V->12V converter that outputs 9A.
Thanks, that makes sense.

The document is a bit confusing; there are two tables on the second page. The 30A 48/12 is in the second table on p2, third last column.
 

jameshowison

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Fuses with clearing times designed to protect semiconductors are rare.

Ask how much $ for two of their internal non-replaceable fuses.

Protecting wire insulation with a 50 year life is much easier.
Ah, so these are the rare times that an (internal) fuse protects the equipment rather than the wire. Hmmm, but Victron says they are non-replaceable so it's odd, they don't seem to protect the equipment and they are at the wrong end of the wire from the battery to protect the wire ...
 

Rocketman

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I believe the non replaceable fuses are so if the dc -dc charger goes up in smoke. The fuse breaks so it doesn’t start a fire with continuous current.

If that fuse pops - your unit is done.
 

HRTKD

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You should have a fuse between the bus bars and the Orion DC-DC converter. The fuse must be rated to handle the near 58V of your 48V system (as your other fuses/breakers must as well).

BTW - I don't see a 48V->12V converter that outputs 30A. I just see a single 48V->12V converter that outputs 9A.

Victron has created a bit of confusion in their product lineup. There is the high power models and then there are the non-high power (my description of this line) models. There is no 48 volt option in the high power line.

High power:

Non-high power:
 
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