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Victron Orion-Tr Smart 12/12-18A, not charging

The Orion DC DC Charger is connected from the Tow Vehicle (TV) via 7 way plug to the Li battery in the Airstream.

With the engine idling, and if the Airstream battery is disconnected, the Orion provides stable power at relatively low load (< 5 amps). Input from the TV is 13.4 or so and output from the Orion is 14.2v. Once the Airstream battery (200 Ah) is connected to the system, the input voltage into the Orion drops to about 10v and the charger goes offline.

What would cause such a significant voltage drop once it is supposed to start charging? Is this a symptom of a bad starter battery and/or bad alternator? The TV has not had any issues starting and charging the battery, but it somehow cannot deal with what the Orion charger is demanding from it to charge the Li battery.

orion dc-dc
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2 Answers
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Mike Dorsett answered ·

Tow vehicle alternator is probably not producing much power at idle rpm, HOWEVER: you should not be seeing that sort of volt drop once the load to the Orion is connected.

Check that your wire sizing, is correct, all connections clean and tight, and the ground is good. check the voltage at the TV Battery and alternator at the same time. Measure all voltages with respect to a single common point i,e, TV battery negative, so measure TV battery, chassis to TV battery negative, TV battery negative to Orion negative and positive input, TV alternator body to TV battery negative and alternator output to TV battery negative. You may need to extend the voltmeter negative cable to do the tests.

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sto answered ·

Hello Mike, I believe your diagnosis is spot on. The installer used some 10 AWG wire while it should be 6 AWG according to my calculations.

The 7 way cable that runs from the 7 way plug at the TV to the junction box is 10 AWG, and that's just how these cables are. That run is short, maybe 4'. https://www.etrailer.com/Trailer-Wiring/Hopkins/H20043.html

From the junction box to the Orion it is about 20' and I would use a 6 AWG wire for that longer segment. Do you foresee any issues with the relatively short 10 AWG segment?

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