Placement of Orion DC-DC chargers

DIY
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1

Hi,

I have a Fountaine Pajot Saba 50 catamaran with a Victron system and a 12V lithium bank (5x300Ah).

The original installation was not satisfactory, so we redid the system and added 2x Orion XS DC-DC chargers to utilize the alternators.

My intention was to have one Orion per engine, mounted as close as possible to each engine/starting battery.

However, the installer has placed both Orions in the port engine compartment. This means the starboard engine has approximately a 7 meter cable run to its Orion. The installer states the cable is 25mm².

From the system readout:

  • Port engine: 13.84V / ~49.5A

  • Starboard engine: 13.82V / ~48.3A

So both units appear to be working and relatively balanced, with only ~0.02V difference.

My questions:

  1. Is this cable length (approx. 7m, 25mm²) acceptable for an Orion XS at ~50A?

  2. Would you consider this placement suboptimal, or acceptable in practice?

  3. Is there a real risk of alternator stress or efficiency loss in this configuration?

  4. Would moving the starboard Orion closer to the engine provide a meaningful improvement?

Appreciate any input from the community.

Thanks
Michael

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2

The 13.8V you are comparing are the output voltages of the two Orions, since thats what matters most. But since they are both running at close to 50A we can assume that the input voltage is sufficient.

Since the Orions are battery chargers its best to place them physically close to the battery they are charging, not the one that provides the power. Since they are also buck/boost converters, they can compensate for input voltage loss. You got them connected to a GX, so if you also have a Shunt and DVCC is active then they also compensate for output voltage loss.

25mm2 with 50A flowing over it, over 7m distance, will result in approximately 4.5% voltage loss. Not great but also not bad.

Risk of alternator stress is given by the current that is being pulled from each alternator as well as ambient temperature. The current doesnt really change whether the Load is close or far away. If your alternators are 100A and above then i would not worry. If they are 100A to 70A then maybe check their temperature a few times during prolonged charging, just to be sure. Alternators below 70A i would not be comfortable with pulling 50A for a prolonged time.

3

Hi chrigu,

Thanks a lot – really helpful and balanced explanation.

Good point regarding the Orion output vs input. I agree that since both units are delivering ~50A, the input voltage is likely sufficient despite the cable length.

For context, my engines are Volvo Penta D2-75, each with standard alternators (I believe around 115A).

Based on your comment, that should put me comfortably in the range where drawing ~50A per alternator is not a concern, but I will monitor temperatures during longer charging periods just to be safe.

Your point about placing the Orion close to the battery rather than the source is interesting – that’s slightly different from what I initially assumed, but makes sense given the buck/boost behavior and DVCC.

I’ll do some measurements next time I’m on board:

- Alternator voltage (B+)

- Orion input voltage

- Check for any heat in cables/connectors

If the voltage drop stays within a reasonable range and no thermal issues appear, I’ll probably leave the installation as is.

Thanks again for the input – much appreciated.

Michael