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stoverjason avatar image
stoverjason asked

Orion XS Cable Sizing and Voltage Drop

Hello all,

I'm looking to install an Orion 12/24-15 DC-DC charger. I'm going to install the current model (15 amps) but wire it large enough for the future Orion XS 12/24 which I assume will be 25 amps (24V)/50 amps (12V).

I have a 33ft RV and the 24v batteries are in the rear (almost all the electrical system is located in the rear on my rig). The Orion can take up to a 4 awg wire. However, when calculating the voltage drop, I would need roughly 1/0 AWG wire to keep the voltage drop below 5%. At 4 awg, the voltage drop is 10.6% dropping the voltage from 14v down to 12.5v. The draw goes from 50 amps to 56 amps.

Is it a big deal to use 4 awg even though the voltage drop is 10%?

If the voltage drop is a big deal, do I simply terminate the 1/0 at a bus bar and then run a short 4awg from the bus bar to the Orion?

Thank you all for your shared wisdom.



orion dc-dc
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3 Answers
nebulight avatar image
nebulight answered ·

I would put the orion as close as possible to your starter battery and have your longer run be the output since higher voltage is less current and thinner wire. That's how I plan to install mine.

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stoverjason answered ·

That's interesting because everything that I've read is that you want the Orion as close to the battery as possible. The problem is that you have to compensate (increase the charge voltage) for the voltage drop on the charger side whereas you do not have to worry as much on the supply side.


Now I'm even more confused if the advice I've been given (put the Orion as close to the batteries as possible) has been wrong.

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nebulight avatar image nebulight commented ·

In theory, yes you do want to minimize voltage drop on the output because the charger won't be able to see the battery voltage. In practical terms, I'm not running a 1/0 cable for a 25 amp charger. :)


Hopefully with the new Orion XS, if you have a GX you can use DVCC (or ve.smart networking if you don't have a GX) to compensate for the voltage drop by reading the battery voltage from the battery monitor. This should solve the voltage drop problem on the output and the cable size problem. I think the latest firmware for the Orion XS supports both, but not sure about the yet to be release 12/24. However with your Orion NON-XS you have neither.

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Sarah avatar image
Sarah answered ·

Hi @stover.jason when using an Orion it is best practice to place it as close to the battery being charged as possible (as the Orion cannot automatically compensate for voltage drop). That said when using a 12/24 Orion the voltage drop will be different depending on whether it is on the supply (12 volt @ 30A) or output (24 volt @ 15A) side due to the different currents. Hence in this case the recommendation to keep the 12 volt leg as short as possible. The ultimate decision is up to you as both will work.

Future versions of the Orion XS 12/24 (no announcement yet regarding availability) with their built in intelligence should be able to get a feed of battery voltage to allow for compensation of output voltage drop as per mppt controllers.

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