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.

brulaz wrote: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?Sounds like a good plan to me, that's a common method for high wattage car audio amps. Split the end of a fat cable into a short runners and crimp ends onto them.brulaz wrote: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? What's the instructions say? Your chassis ground should be at 0 volts, so I think that's the safe ground to use, and the shortest path. Same trick with the fat cable to twin connectors should work here too.

brulaz wrote:The 24V and 12V systems on the Victron have a common neg (are not isolated).Do you have 2 connectors each for input and output? My 48v Orion has that. I didn't connect anything to 'ground.'

hows it work without ground? it's a switch mode buck converter, it's gotta be grounded somehow?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.

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.

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.

Wiring a 24V to 12V converter | Good Sam Community

2oldman
Explorer II
Apr 18, 2017
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.
GordonThree
Explorer
Apr 18, 2017
hows it work without ground? it's a switch mode buck converter, it's gotta be grounded somehow?

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.
2oldman
Explorer II
Apr 18, 2017
brulaz wrote:
The 24V and 12V systems on the Victron have a common neg (are not isolated).
Do you have 2 connectors each for input and output?

My 48v Orion has that. I didn't connect anything to 'ground.'
GordonThree
Explorer
Apr 18, 2017
brulaz wrote:
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?

Sounds like a good plan to me, that's a common method for high wattage car audio amps. Split the end of a fat cable into a short runners and crimp ends onto them.

brulaz wrote:
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?

What's the instructions say? Your chassis ground should be at 0 volts, so I think that's the safe ground to use, and the shortest path. Same trick with the fat cable to twin connectors should work here too.

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Wiring a 24V to 12V converter

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