Wire size question for Victron Orion XS DC-DC 50amp charger

[dhays]

I am starting to plan the installation of the DC-DC charger, hopefully this weekend. Victron is confusing me however.

In Victron's installation instructions they mention cable size for the input and output wire three times.
- if you use 8, 6, or 4 AWG wire, you don't need to use ferrules to connect the wire to the input/output screw terminals. If you use thinner wire, then a ferrule can be used.
- Recommend a 60-70amp fuse. If cable run is 5-10m, then use 4 AWG wire. If cable is <5m then 6 AWG wire is recommended.
- Torque settings for the screw terminal connections are given for 4, 6, 8, 10, 12 AWG wire.

I want to use maxi blade fuse holders for the fuses. I am having some trouble sourcing good quality 6 AWG Fuse holders. Easy to find 8 AWG fuse holders. The wire runs will be less than 2 feet to Bus bars which are connected to the batteries and the ground with 4/0 cable. So can I use 8 AWG wire for this or should I keep trying to hunt down 6 AWG fuse holders?

 

[DDW]

Can you use MRBF teminal fuse blocks like this one? They can bolt right to the bus bar, and the cable bolt right to them. I like these where they can be used, they are self mounting, and the unprotected cable run is zero. For cables of any size that are connected to a high energy bus, that can be important. You can get them anywhere, West, Amazon, etc.

If you are set on maxi fuses, Blue Sea makes a holder that is high quality, and will take wire down to #4. Often fuses are rated based on the cable size attached (as the cable is a heat sink for them), so underizing the cable can be a bad idea. Thought #8 is technically capable of carrying 50A, but there will be some voltage drop, even in 2'. I've had the molded-in-line type maxi fuse holders melt at substantially below their rating, so I am leery of them.

 

[Comodave]

Check the interrupt current requirements too.

 

[dhays]

I hadn't thought of using a MRBF fuse. I do have those on my batteries. I may not have enough room for them however. I will check. One advantage to those it it would mean fewer crimp connections, particularly with 6 gauge wire.

If I have room I may consider using some of the Midi fuse holders.

 

[cafesport]

For a tr 24 volt installed three years ago I used a 30 amp blue seas mrbf fuse and 6 awg wire. The max output is rated for 700 watts, but because of the heat produced and the settings it is programmed to operate at it at it never outputs much above 400 watts. There was a .6 volt drop from the output side to the busbar but you can program it to boost to maintain the correct charge profile. Still waiting to see a 24 volt xs, still vapor ware apparently.

 

[J.T kearney]

Hi Steve D had some great imput on your install. Mine is a 150/50 mppt victron requiring a 60 amp fuse at the battery. Went with 60 MRBF to 4 gauge, then to ON/OFF switch about 6 ft away. From there used 8 gauge to MPPT controller about 1 ft away, because that is the largest gauge I could get in the MPPT controller!! Then with 10 gauge to a dbl pull breaker about 1 ft away from the Mppt controller to the solar panels.
Cheers J.T.

 

[dhays]

Well, I decided that since 6 AWG was going to be a bit of a hassle (my crimper won't handle anything bigger than 8 AWG) I decided to get a new crimper and go with 4 AWG wire. Still not sure on the fuse. I will be connecting to bus bars that are connected with short runs to the batteries with 4/0 cable, and need to see if I have room for MRBF fuses on the bus bars. If not, I will likely use ANL or AMI/Midi fuses.

 

[dhays]

A follow on question. For size reasons I am looking at using AMI fuse holders (if I can't get the MRBF terminal fuses to fit). The AMI fuse holders use M5 studs. I can't really find 4AWG - M5 ring crimp connectors. I can easily find 4 AWG - 1/4" (M6) ring connectors.

Any issues with using 1/4" ring over a M5 bolt? The fit would be a little big, which I don't like, but should be a good enough connection? I think so, but I'm ignorant.

I could so with the larger ANL fuses, but that really increases the space required which is already going to be tight.

 

[Mambo42]

Victron prescribes 1 mm2 per 3 Amps, so that would mean 17 mm2 which does not exist in AWG (as far as I can see).
That would leave you with 4 AWG, but you may want to check if that is going to fit in that charger, as I found out with my MPPT controller that it did not fit.

 

[cafesport]

The specs in the manual show max wire dimension of 4 awg and suggest 50 a 50 amp fuse. Blue seas has them with m8 or 5/16”

 

[dhays]

The specs in the manual show max wire dimension of 4 awg and suggest 50 a 50 amp fuse. Blue seas has them with m8 or 5/16”

I haven't seen the 50 amp fuse recommendation. What I did find was this from the Victron Orion XS 12-12-50A DC-DC Charger manual. However, I could have missed it somewhere.

 

[dhays]

Victron prescribes 1 mm2 per 3 Amps, so that would mean 17 mm2 which does not exist in AWG (as far as I can see).
That would leave you with 4 AWG, but you may want to check if that is going to fit in that charger, as I found out with my MPPT controller that it did not fit.

Yes. My Victron MPPT controller will only take up to a 6 AWG wire. However the Orion DC-DC charger accepts (so they say) a 4 AWG wire.

 

[luna]

If I was doing this I would consider using a couple of circuit breakers like a Blue Seas 187 series #7140, which could be as far as 40" away from the bus bar if the conductors are sheathed. They also serve as a conveniently placed disconnect switch, plus you never need to stock yet another spare fuse.

The AIC rating of whatever you use should not be an issue if you attach to the existing bus that is already protected by a class T fuse.

 

[cafesport]

I used those CB’s on a charger, also a good option. Here’s the specs from the xs manual.

 

[dhays]

I used those CB’s on a charger, also a good option. Here’s the specs from the xs manual.

Thank you. I am generally ignorant on all things electrical, but I'm confused by why Victron seems to recommend a 60a-70a fuse for the battery connections in Section 3.3 of the manual if the maximum short circuit voltage is 50amp.

 

[Kayl]

I ran into the same issue when I was setting up my DC-DC charger. I ended up using 8 AWG fuse holders because I couldn’t find 6 AWG ones that weren’t overpriced or hard to source. Since your wire runs are pretty short (less than 2 feet) and you’re using 4/0 cable, 8 AWG should work just fine. Just double-check that the fuse holders can handle the amps you're dealing with. Quality is key here, so make sure they're decent.

 

[luna]

Victron as well as most other electronics manufacturers will recommend an overcurrent device (fuse or C. B.) 20 percent or more above the input or output rating of their device simply to eliminate the nuisance trip associated with a 50 A fuse on a 50 A circuit.

The Customer Support Department was happy with that recommendation.

 

[dhays]

Victron as well as most other electronics manufacturers will recommend an overcurrent device (fuse or C. B.) 20 percent or more above the input or output rating of their device simply to eliminate the nuisance trip associated with a 50 A fuse on a 50 A circuit.

The Customer Support Department was happy with that recommendation.

Thanks. I've got 70 amp fuses on the way. I was thinking about using a CB, but decided to go with a simple AMI fuse.