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jan-willem avatar image
jan-willem asked

Phoenix Inverter 12V 375V, 230V - Meaning 'Voltage for discharge current'

I have put together an off-grid system to build up knowledge and experiment with it.

Setup

  • 2x connected in series, self-built solar panel, (81W / 9V per panel) = 162W / 18V total.
  • Victron Smartsolar-mppt 75-15
  • Victron Phoenix Inverter 12V, 375VA, 230V
  • Victron AGM battery Deep Cycle 12V 90Ah

With a small load, the inverter gives an alert fairly quickly that the voltage is too low.

I have a question about the inverter settings that can be made via the app.

In the accompanying documentation and on the Victron website I have searched everything for the meaning of settings, but I cannot find this information. I may be overlooking something.

In the section 'Dynamic cut off' it is possible to adjust 4x the voltage at 'Voltage for discharge current'. At 0, 23, 63 and 180A.

What is the significance of this?

discharge level
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2 Answers
ripper avatar image
ripper answered ·

That is indeed silly, this device will hardly ever draw 63 or 180 amps. But they use the same points for all inverters to make it possible to adjust the discharge graph on 4 points rather then just one and that makes sense.


Through inner resistance in the battery, voltage of the battery drops further the higher the load is. Lead has espacially high inner resistance. A Lipo will hardly drop. A 5W load will run for days on a given lead battery and show 10V. It is then overly depleted and getting damaged. You want to set the 0A value to a much higher 12V. A high load of 63A at 2x 375W for startup of a vacuum for milliseconds on a fully charged battery will make you see 10, 6 V on the battery connectors. The inverter might now shut off because you set it above to 12V on a single point. Here you have the possibility to set a 63A point to 10,5 V and your vacuum will start. If your inverter could sustain this load your fully charged battery might hold up for 2 minutes or so If the battery is not fully charged it will drop further after 30 seconds and is again protected. You can set one more point to your liking between these points and that would make sense for the 375 device. For whatever makes sense or which you dont want your battery to go under, under load.

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jan-willem avatar image jan-willem commented ·

Hello Ripper,

Thank you too for your comment and explanation. Got wiser again :-)

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Stefanie (Victron Energy Staff) avatar image
Stefanie (Victron Energy Staff) answered ·

Hi @Jan-Willem,

I'm not sure to which document you're referring in regards to "4x the voltage at 'Voltage for discharge current'. At 0, 23, 63 and 180A.".

The dynamic cut-off is pretty well explained in this document: Dynamic Cut-off in the Phoenix Inverters


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jan-willem avatar image jan-willem commented ·

Hello Stefanie,

Thank you for your comment. By documentation I mean the help function present in the app. In it an explanation is given about the app where what is stated, but not the meaning of the options. The link you give certainly makes a lot clear about Dynamic cut-off.

To clarify, here is a screen print of the relevant part in the app:

9de3c49a-0dd6-4d84-abb0-ba83fc3f604e.jpeg

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9de3c49a-0dd6-4d84-abb0-ba83fc3f604e.jpeg (490.3 KiB)
Stefanie (Victron Energy Staff) avatar image Stefanie (Victron Energy Staff) ♦♦ jan-willem commented ·

Ah ok, I see what you mean.

The discharge currents are just numbers to determine a cutoff voltage, appropriate to the loads because of the expected voltage drops. These currents are assumed numbers for all the loads in the system, not the loads of the phoenix inverter.

As explained in the document, the higher the load, the greater the voltage drop, the higher the chance of a cutoff - unless you have corrected the cutoff voltage (depending on chemistry of your battery, Lithium vs. Lead Acid and overall capacity).

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jan-willem avatar image jan-willem Stefanie (Victron Energy Staff) ♦♦ commented ·

Thank you Stefanie!

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