Fuse and distribution for 48v loads (inc 48-12 converter)

jameshowison

Solar Enthusiast
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Jul 30, 2021
Messages
95
I am planning a 48v battery system that includes a few 48v loads. I'm trying to understand the options for fuse to protect the wires to the 48v loads.

The loads are:
1. 48v-12v 30amp Orion converter (draws 10amp at 48v)
2. A 48v HVAC system (draws max 30amp at 48v)
3. Possibly a 48v hot water element (drawing, say, 15amp at 48v)

So looking for fuse options similar to 12v loads, but it seems that fuses are voltage sensitive (learning stuff all the time :). Options found so far:

0. Victron Lynx Distribution (not an option because only MEGA fuses at high amps, or DIY make Midi fuses fit, but unit is massive and not needed for the smaller wires in a 48v system).
1. MBRF terminal fuses (but only go down to 30amps). e.g., https://www.bluesea.com/products/5196/MRBF_Surface_Mount_Fuse_Block_-_Common_Source
2. Victron MIDI fuses (but only go down to 30amps, shown in the price list as "MIDI-fuse 30A/58V for 48V products")
3. Auto "58v" MINI fuses (good range of smaller sizes up to 30amps). e.g., https://www.littelfuse.com/products/fuses/automotive-passenger-car/blade-fuses/997.aspx

Each requires a different kind of holder. I was hoping for a "power distribution" bus bar approach (like the MBRF one above and the Victron Lynx Distribution. There seem to be those options for the MBRF, but I'm particularly confused about the MINI 58v fuses. Can those 58v MINI fuses fit in the MINI fuse distribution panels? ie something like this: https://ceautoelectricsupply.com/wp-content/uploads/2016/06/MINI_Fuse_Block_with_Cover.jpg Does anyone know a high quality option (Bussman, EATON, Blue Sea etc)?

Failing that should I just use a bus bar with multiple inline fuse holders. e.g., The littelfuse FHM2 https://www.littelfuse.com/media?re...=littelfuse-fuse-holder-inline-mini-datasheet

Or should I go with the MBRF or MIDI fuses and just use larger cable than needed (ie use the minimum size fuses at 30amp and match the cable to that?).
 

Johncfii

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Joined
Nov 24, 2020
Messages
264
I see nobody replied to your post. Maybe you already selected your solution, but . . .

Fuses are only voltage sensitive with respect to maximum voltage. A 58-volt rated fuse is appropriate for 12, 24, or 48 volts, anything up to 58 volts, and probably quite a bit over 58 volts. The potential issue is arcing across the gap in the open fuse, especially for inductive loads, like transformer windings, or motors, where the reverse EMF can spike quite a bit higher as the magnetic field collapses in the instant the fuse opens. It is a REALLY small risk, but with lawyers making the calls . . . The current rating of the fuse is not dependent on the voltage of the fused circuit.

In our travel trailer, I use the MIDI/AMI fuses for DC distribution. I like the tabs with holes that allow screw mounting. That gives wide option to accommodate wire sizes. But I thought holders to be unnecessarily expensive. I fabricated my own out of 1/4“ thick scrap aluminum bar stock, attached to a scrap of oak lumber. I like to fab my own stuff that is low cost, and better than what can be purchased for any reasonable price.
 

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