question

oxy avatar image
oxy asked

Orion-Tr Smart 12/12-18 through 2.5mm2 tow cable harness?

Hi everyone, I'm looking for a DC-DC converter to charge caravan's leisure LyFeYPO4 battery from the tow car. Cables in the car are 6mm2. Similar are cables inside the caravan too. However, the 13-pin socket uses an off-the-shelf harness, which comes with 2.5mm2 cables for battery charging on pin-9 - this "bridge" (the weak link) between the car and trailer is about 2 meters in length... I read in various tables that 2.5mm2 is 16A nominal, BUT it is capable of up to 21/25/27A (sources differ). I understand I'm reaching the copper limits here! Hence the question: is it possible to run Orion 18A model with this "weak bridge" in between the car and caravan? Ideally, I'd like 15A, but Victron doesn't have such. With 18A/0.87 efficiency=20.6A pull through the 2.5mm2 two meter tow harness, it still seems to be "possible"? For reference, I have measured the fridge on a similar dedicated 2.5mm2 pin-10 wire: it's consuming 16A - the wires are only tiny warm. So, I know that 16A is safe. Would Orion's 18A (~21A more precisely with efficiency in mind?) additional +5A be of issue? What Orion does when voltage drop in wires happens? Does it change the current? What maximum fuse current would be acceptable for such a 2.5mm2 wire? Thanks a lot! p.s. It'd be great if Orion current was adjustable, then I'd just drop it to ~15A and all was well :)

orion-tr smart
1 comment
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

oxy avatar image oxy commented ·

p.s. Sorry for the formatting - all my new lines got lost after sending through mobile!

0 Likes 0 ·
2 Answers
kevgermany avatar image
kevgermany answered ·

You will see a 1V drop through this section at 18A, will increase as current increases to compensate for the voltage drop. The other issue is heat, possible wiring burn out.

The Orion will work, but likely that engine auto detect can't be set up properly.

Probably best to bypass with heavier gauge wire.

If the power feed to the tow hitch isn't switched by the towvehicle ignition, add a circuit to switch on the Orion using the L and H pins (check the manual, it's downloadable). Otherwise the Orion may drain your starter battery.

2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

oxy avatar image
oxy answered ·

Thank you for your confirmation @kevgermany . Incidentally, I was calculating the voltage drop just this instance with this tool and got a similar number :)


What puzzles me is whether Orion is a "buck-boost" converter or not? I.e. if the voltage at wires drops down to say 12.5VDC (or even lower) due to resistance, will it "boost" it to the wanted 14+VDC?

I know that there's another converter from Victron which is advertised as buck-boost, but it's rather expensive and the software requires Windows: https://www.victronenergy.com/dc-dc-converters/buck-boost-dc-dc-converter-25a-50a#software

Noted your point about engine detect.

1 comment
2 |3000
Toggle Comment visibility. Current Visibility: Viewable by all users

Up to 8 attachments (including images) can be used with a maximum of 190.8 MiB each and 286.6 MiB total.

kevgermany avatar image kevgermany ♦♦ commented ·
AFIK it uses buck/boost to control the output voltage. But it's more, has the engine detection, and charge profiles.

As long as the input voltage is above the cut off setting, it will continue to charge. So if input is at 12.5V and the cut off is lower than this, it will charge up to the absorption voltage, say 14.4V. Or whatever it's set to.

0 Likes 0 ·