Proper fusing for dual 2 AWG Cables in 12V RV system

soylentgreen
soylentgreen Solar Expert Posts: 111 ✭✭
in Off Grid Solar & Battery Systems #1
I inherited a RV that was heavily modified by the previous owner. I've recently come to realize that the inverter wiring is not fused at all, and I want to improve that.

The setup:

2x Trojan T145s (6V each), wired in series to make a 12V bank. Each battery is wired to the other with two 2 AGW battery cables in parallel. (The cables are in parallel, but the wiring is series, if that makes sense).

2000W Inverter, connected with dual 2 AWG marine-grade wire. This inverter seems to be designed for this setup (it has two positive and two negative inputs, each accepting 2AWG). There are 2 red wires and 2 black wires. The battery to inverter wire length is about 4 feet.

My understanding is that with dual wires, one must be careful: if you treat the 2 wires as one big wire and put in a big fuse, this is dangerous: if one of the wires is disconnected or cut, then the 2nd wire can be subject to the full amperage, which will then overheat, before the fuse trips.

By my calculations, 2AWG is just about the same as 2/0 (00 AWG) wire.

My plan: Blue Sea Dual MRBF Terminal Fuse block, which connects directly to the + side of the battery, and then hook each 2 AWG wire to a separate 150A MRBF fuse.

Questions:
* is that the right way to fuse it (each wire with its own fuse?)
* is 150A for each 2 AWG wire the right size?
· Share on Twitter

Comments

  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #2
    Re: Proper fusing for dual 2 AWG Cables in 12V RV system

    Hmm. Two positive and two negative posts on the inverter? Does it say "AIMS" on it by any chance?

    You are correct in your wiring & fusing: each 2 AWG line needs to be protected individually so that if one fails the other won't be forced to take potentially 200+ Amps. Using a Blue Sea dual battery post fuse holder with one 150 Amp fuse per wire should work fine.

    And yes parallel 2 AWG has about the same resistance as 2/0, and slightly higher current rating due to better heat dissipation (more surface area).
    · Share on Twitter
  • soylentgreen
    soylentgreen Solar Expert Posts: 111 ✭✭
    #3
    Re: Proper fusing for dual 2 AWG Cables in 12V RV system
    Cariboocoot wrote: »
    Hmm. Two positive and two negative posts on the inverter? Does it say "AIMS" on it by any chance?

    Posts? Dear young Padawan, you are not skilled in the lore of "bargain-basement" inverters. This is better. This has two, uh, wire-cups, into which one, uh, scrunches, some 2 AWG wire and then tightens a set screw which kind of screws its way into the wire bundle, and then, somehow magically, it's a Connection! Vulcan mind meld, or something.
    Cariboocoot wrote: »
    You are correct in your wiring & fusing: each 2 AWG line needs to be protected individually so that if one fails the other won't be forced to take potentially 200+ Amps. Using a Blue Sea dual battery post fuse holder with one 150 Amp fuse per wire should work fine.
    And yes parallel 2 AWG has about the same resistance as 2/0, and slightly higher current rating due to better heat dissipation (more surface area).

    Ok, cool : I'm glad to hear I haven't totally misunderstood the rules & calcs.
    · Share on Twitter
  • Cariboocoot
    Cariboocoot Banned Posts: 17,615 ✭✭✭
    #4
    Re: Proper fusing for dual 2 AWG Cables in 12V RV system

    Indeed; I have a 600 Watt inverter with that kind of connector (4 AWG max), but I wouldn't dream of trying such a thing for 2000 Watts and/or 2 AWG. :roll:
    · Share on Twitter
  • soylentgreen
    soylentgreen Solar Expert Posts: 111 ✭✭
    #5
    Re: Proper fusing for dual 2 AWG Cables in 12V RV system

    To be fair, the inverter (A Vector Maxx SST Vec054C) does work pretty well: It handles a 500W Air Conditioner with surge startup current, or a 1500W vacuum cleaner, without breaking a sweat. I don't particularly like the way the 2AWG wires hook up, but it does seem to work fine.
    · Share on Twitter
  • smatthew
    smatthew Registered Users Posts: 15 ✭
    #6
    Re: Proper fusing for dual 2 AWG Cables in 12V RV system
    Cariboocoot wrote: »
    Hmm. Two positive and two negative posts on the inverter? Does it say "AIMS" on it by any chance?

    I believe Victron uses double posts on some of their larger inverters. IE Their quattro models use 4 M8 bolt on connectors (2 positive, 2 negative). Even they don't clearly lay out how to fuse them correctly.
    · Share on Twitter

Categories