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Orion XS Low Output with Audi Q7

We have a 2017 Audi Q7 towing our Airstream travel trailer. I installed the Orion XS to the charge line originating from the Audi. The Q7 is fused to 15A so the XS is set to 15A input limit.

I'm seeing good charging of our lithium batteries in the 13A range to the batteries for about an hour or so when traveling. However, it gradually drops to around 4A and stays there even though the batteries are nowhere near charged.

In the sun, the 300W solar roof panels were chugging along at 250W or so and around 10A. I thought it might be something weird with the controllers and disabled the rooftop solar charger, but still got the same 4A. I disabled VE.Networking, still the same.

So, I'm left with something to do with the TV (Audi Q7) alternator or system. It was a hot day so maybe with the A/C running there's too much load and it throttles it back? I think it's a 180A alternator. Or is there something with the XS I don't have set up right?

Attached shows charging at start then when the charger is operating at much less than it should and settings.

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orion dc-dc
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chrigu avatar image
chrigu answered ·

The input voltage is lower on the second picture. The orion regulates the charging power to keep the input voltage above the shutdown voltage (13.1V).
Are you using the original audi cabling to feed the Orion?
Theres also a temperature warning and a fault listed in the manual, but im not sure if the device starts to derate before theres a notification

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jeffk avatar image
jeffk answered ·

Thanks, I could try lowering the shutdown voltage, but it appears to be not shutting down. The cabling is the trailer umbilical cord which is 10AWG.

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chrigu avatar image
chrigu answered ·

But the Orion is located in the trailer? So you got long, relatively thin cabling, with a trailer plug in the mix as well. All factors that drive the wire resistance up, leading to higher losses. You can for some degree compensate for that trough settings, but ultimately its turning the cabling into a heating element.

I can only assume the total cable length involved. According to the wiring unlimited handbook of victron, for a total of 16m (thats 8m of positive and 8m of negative cable) at 16A, they recommend a 16mm2, thats AWG5. I guess AWG5 is only theoretical (is not being produced), so in reality it would need to be be AWG4

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jeffk avatar image
jeffk answered ·

Yes, Orion is in the trailer. Yes, possible the wire gauge is too small, but it looks like 10AWG will handle 15A up to 6m or so. It's hard to say what the distance is. Since it's fused at 15A I would guess that's what Audi thought it could handle. In any case, maybe there's some voltage drop but I'd expect more current and initially this is the case.

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Andrew Ford avatar image
Andrew Ford answered ·

I have battled performance issues with my older Orion 12/12-18 and it is very hard to nail down the root cause. I feel like there are many possible contributing factors and your best bet is to address them all individually and see if any performance increase occurs.

In my case, I have determined that the most likely cause of my issues is the derating when the device gets warm. I understand the Orion XS is more efficient than the older ones so hopefully that's not the problem but I would check the ambient temp of the location in which the XS is intalled to see if it's getting warm in there. That might explain why it gets worse over time, like with mine.

Next I would consider a dedicated, thicker cable from the Audi to the trailer. I run 6awg from the starter battery to an anderson plug at the tow bar, then it's also 6awg from there to the DCDC charger. This should result in pretty minimal voltage drop, which will improve your chances of getting good performance. I have a basic alternator so am not personally familiar with how smart alternators behave in the real world but I would expect it to be the same in that you want as little voltage drop as possible.

I am curious how you got the XS working in a camper. I have been holding off for an isolated version because I thought you needed that when there wasn't a common ground, as per in a trailer. Wonder if that has anything to do with it.

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chrigu avatar image chrigu commented ·
A smart alternator isnt that smart. Its got a can bus interface, delivers information about voltage, current and temp to the car and receives a voltage or power setpoint from the car.

The car then raises the setpoint in situations that need engine braking, so the alternator will charge the starting battery and helps slow down the car.

On the other hand the setpoint gets lowered in situations that need power from the engine, like hard acceleration, so you get an extra 1/2hp to the ground.

Further, the car measures the Ah going out of and into the starting battery. Starting the engine uses lets say 5Ah, so the alternator will run at the higher setpoint until that amount is recharged, then its output is lowered.


This will result in more fuel efficiency, hopefully. But also leads to varying system voltage in the car. For my work van, 12,3V at engine off, 13,0V at engine running but alternator "off" and 14,4V if the alternator is charging.


Trailer wiring certainly is different between US and EU. In europe the trailers ground is on the trailer plug, so whenever its plugged into a towing car, they both share a ground

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jeffk avatar image jeffk chrigu commented ·

It's the same in the US, the ground is common, so @Andrew Ford you don't need an isolated charger.

I really, really don't want to run a separate wire from the alternator. On the Q7 I'm not sure how to accomplish this. I will live with it for now, but it's a bit of a bummer.

@chrigu, thanks for the explanation. I didn't know how that worked. So it might be something in the vehicle that's limiting the current.

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