Forum Discussion

brulaz's avatar
brulaz
Explorer
Apr 18, 2017

Wiring a 24V to 12V converter

Went crazy and decided to upgrade to a 24V system (and 2000W inverter).

Ordered a Victron Orion 24/12-40 converter for the 12V stuff (except emergency brake switch). It's rated 40A continuous output with 55A peak and is non-isolated. The converter will be located about 5' from the batteries.

Issue 1:
Just now noticed the Victron uses *two* 6.3mm Faston tabs for each of +24V, +12V and the common neg. And the manual says you should run two parallel cables for all three in/outputs when over 25A output is expected. So that sounds like I want two 10awg lines each with a big yellow AMP Faston female connector for every in/output.

But as I've already got lots of 6 awg cable available and in place, am thinking of just splicing/soldering very short sections 10 awg, with the Fastons on one end, into a single 6 awg cable for each of the three in/outputs?

Issue 2:
The 24V and 12V systems on the Victron have a common neg (are not isolated). Does that neg get wired to:
the 24V battery neg,
the chassis ground attached to battery neg,
a chassis ground nearer the converter?

Any suggestions or comments appreciated.
  • time2roll's avatar
    time2roll
    Nomad
    Apr 18, 2017
    Unless the converter is portable just use heat shrink butt connectors.
  • 2oldman's avatar
    2oldman
    Explorer II
    Apr 18, 2017
    brulaz wrote:
    Just checked the Victron site. The only 48V converters I see are all Isolated. They are not common ground, non-isolated like my 24V Victron.
    Ok. I still have my Victron 24v unit. I'll have a look at it. My biggest amp draw is for my slides, so far no problems with the Fastons. Congrats on the 24v. What I really like about your setup (and mine) is the 12v side voltage never varies. Those Victron units are good quality stuff and hold the voltage right where you set it.

    GordonThree wrote:
    Ok so the minus on your 48v side is 0v right?
    I don't know.
  • brulaz's avatar
    brulaz
    Explorer
    Apr 18, 2017
    2oldman wrote:
    GordonThree wrote:
    hows it work without ground? it's a switch mode buck converter, it's gotta be grounded somehow?
    Its 12v may be grounded post-converter somewhere in the trailer. I imagine it is, just never looked. 48v side is just a +/- from batteries.


    Just checked the Victron site. The only 48V converters I see are all Isolated. They are not common ground, non-isolated like my 24V Victron.

    Think that explains the confusion.

    So unless someone suggests otherwise, I'll just connect the converter neg to the close-by chassis ground. And NOT run a cable back to the battery neg or battery chassis ground.
  • brulaz's avatar
    brulaz
    Explorer
    Apr 18, 2017
    MEXICOWANDERER wrote:

    ...
    Do whatever it takes to find larger wire size PACKARD female terminals. They have a ramp tang inside that increases conductive area contact surface.

    I've not seen anything larger than 10-12 gauge Packard terminals and they are never encased. Always bare. With care solder 10 gauge AWG wire to the inside tang then crimp the top tang to the wire insulator. I cover with 3:1 heat shrink tubing.
    ...


    Searched ebay and found "12084590 Delphi Metri-Pack Female 630"
    Looks like just the thing. A metric female Packard connector by Delphi.

    The 630 refers to the 6.3mm prong size. And they can handle wire up to 5mm wire, so 10awg works. They also claim 46A current capacity.
  • brulaz's avatar
    brulaz
    Explorer
    Apr 18, 2017
    GordonThree wrote:

    ...
    Wow they're really silent on details on the website. Guess they mainly lean on custom installers to do the hookups?

    I'm stumped, no hands on experience with this particular product. Non-isolated DC-DC converters I've designed only had 1 ground connection, and I've connected them to chassis ground. The lower voltage devices down stream were also grounded to the chassis.


    So you ground the negative on the converter to a close-by chassis ground rather than run a cable back to the battery neg? It sounds like Oldman2 has a line running back to the battery neg post (and from there to chassis for the 12V).

    By the way, my trailer has 3 main 12V chassis grounding points. One at the front with a short connection to the battery. One close to where the converter will be that has the truck's ground wire and several other high Amp ground wires connected (for the slide, stab.jacks, awning), and one close to the WFCO distribution centre for smaller 12V loads.

    And yes the manual is pathetic. 1.5 pages with 7 languages.
    Victron wrote:
    1. Select a cool, dry and ventilated area.
    2. First connect the ‘minus’ supply cable to one of the
    minus terminals of the Orion.
    The two minus terminals are interconnected.
    Please note that a bad minus connection could result
    in output overvoltage.
    3. Connect the remaining cabling.

    Then something about the optional remote. At least they also add: "Important note: always use two parallel cables on
    input, output and minus if the output current will
    exceed 25A"
  • brulaz's avatar
    brulaz
    Explorer
    Apr 18, 2017
    MEXICOWANDERER wrote:

    ...
    Do whatever it takes to find larger wire size PACKARD female terminals. They have a ramp tang inside that increases conductive area contact surface.

    I've not seen anything larger than 10-12 gauge Packard terminals and they are never encased. Always bare. With care solder 10 gauge AWG wire to the inside tang then crimp the top tang to the wire insulator. I cover with 3:1 heat shrink tubing.

    When I built the BORG I soldered 3 into 1 wires directly to the terminal block screws and all.
    ...


    Thanks Mex, will look for Packards and try splitting the 6ga wire in two to mount the Packards.
  • GordonThree's avatar
    GordonThree
    Explorer
    Apr 18, 2017
    2oldman wrote:
    GordonThree wrote:
    hows it work without ground? it's a switch mode buck converter, it's gotta be grounded somehow?
    Its 12v may be grounded post-converter somewhere in the trailer. I imagine it is, just never looked. 48v side is just a +/- from batteries.


    Ok so the minus on your 48v side is 0v right?
  • GordonThree's avatar
    GordonThree
    Explorer
    Apr 18, 2017
    MEXICOWANDERER wrote:
    NYET!!!

    These people are stupid! Sorry to be cranky.

    FAST ON is a trade name. Through BITTER HARD EARNED EXPERIENCE I learned standard SPADE TERMINALS S-U-C-K when conducting high amperage. Yeah. Fires.


    Glad you pointed that out. The impotent spade terminal seems underspecified for the task at hand. Odd that a company with Victron's rep would choose it. Wouldn't some 5/16ths studs have been easier?
  • MEXICOWANDERER's avatar
    MEXICOWANDERER
    Explorer
    Apr 18, 2017
    NYET!!!

    These people are stupid! Sorry to be cranky.

    FAST ON is a trade name. Through BITTER HARD EARNED EXPERIENCE I learned standard SPADE TERMINALS S-U-C-K when conducting high amperage. Yeah. Fires.

    Do whatever it takes to find larger wire size PACKARD female terminals. They have a ramp tang inside that increases conductive area contact surface.

    I've not seen anything larger than 10-12 gauge Packard terminals and they are never encased. Always bare. With care solder 10 gauge AWG wire to the inside tang then crimp the top tang to the wire insulator. I cover with 3:1 heat shrink tubing.

    When I built the BORG I soldered 3 into 1 wires directly to the terminal block screws and all.

    Slip-on .250" fast on terminals should always have to be babied on. Tight tight tight. Silicone GREASE helps. My comments are derived from decades of experience not theory. Fast On and me butted heads. I had to fix factory and other technician's screwups.

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