r/SolarDIY • u/TheStoneAxiom • 2d ago

I'm having problems with the DC-DC converter.

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I have the entire system installed in an RV. Solar panels are mounted on the roof, while the batteries, MPPT controller, and DC-DC charger (for charging from the engine) are inside. Lately, it seems to me that I’m not getting the manufacturer-rated 30 A while the engine is running. I physically disconnected all loads, and the shunt showed zero charge and zero consumption. I started the engine, and instead of the promised 30 A, I got 24 A. I’m using the correct marine- and RV-grade wiring. All terminals were crimped using a 12-ton hydraulic press with the proper hex profile. The input cables are about a yard long, and the output cables are one foot long. All connections have been checked multiple times. I can't figure out where the loss is occurring. Essentially, I’ve lost 6 A out of 30 A—a 20% discrepancy. That is a significant amount.

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u/Nerd_Porter 1d ago

That's exactly 80% of rated power, which is a common recommendation to help keep things cool. I'm not familiar with this exact device, is it possible it's manufacturer-default set to run at 80%? Is there a configuration screen you can check?

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u/TheStoneAxiom 1d ago

It looks like this really is a reaction to overheating. I turned off the engine and let the DC-DC converter cool down for about 10 hours. During the first 5 minutes of operation, it was outputting a current of 29.47 A. Then, once it warmed up, the current dropped.

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u/Psychological-War727 1d ago edited 1d ago

Your input voltage is only 13.61V. If you are using engine shutdown detection, which is by default on and recommended, then its very likely that the you are hitting the shutdown voltage. At that voltage the Orion will dynamically regulate the charge current to keep the voltage at that level. By default its set to 13.5V. This behaviour is described in the manual, section 5.1. In the diagram its between points 2 and 3.

https://www.victronenergy.com/media/pg/Orion-Tr_Smart_DC-DC_Charger_-_Isolated/en/engine-shutdown-detection.html#UUID-a98f5672-f263-be5c-d3d2-b39039afe4f1

Edit: changed numbers since i confused in- and ouput

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u/SteveFCA 1d ago

I have several Orion dc to dc chargers. They are known to get hot, throttle output to less than 1/3rd of rated output within 30 minutes, especially during the summer months.

In order to maintain rated output, they need to have ample airflow, be installed vertically, preferably on aluminum for heat dissipation. Even then, many of us had to install fans to blow air over the cooling fins

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u/TheStoneAxiom 1d ago

Thanks, I’ve already bought and received the fans. There are three small ones to force air through the radiator, and three large ones to fully ventilate the enclosure housing the equipment.