Synchronized charging with 2x Blue solar, Venus and Phoenix inverter

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aphexer asked Oct 5, '22

Synchronized charging with 2x Blue solar, Venus and Phoenix inverter

I've got the following off-grid setup:

- 1 BlueSolar 75/15 MPPT on PV string 1

- 1 BlueSolar 100/30 MPPT on PV string 2

- Venus running on a raspberry pi

- Phoenix Inverter

- 12V AGM battery bank

- Smartshunt

The MPPTs & smartshunt are connected to the Venus using a VE.direct-USB cable. The inverter is connected to the Venus using a MK3-USB cable. Both PV strings suffer from occasional shading at different times throughout the day.

Is there any way to enable synchronized charging on both MPPT charge controllers? Either controlled through the Venus, or controlled by an assistant running on the inverter? Right now I get into situations with one controller in float, and the other one still in bulk. One trying to reduce power to reduce voltage, the other doing the opposite...

From the documentation I found so far it seems impossible. Ve.smart networking is not applicable as I'm using Bluesolar instead of Smartsolar. The ESS assistant I can't use because I don't have an AC-in.

MPPT Controllers mppt state

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Modifications Space

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Answer 1 · 2022-10-05T08:57:44Z

ludo answered · Oct 05, 2022 at 08:57 AM

Not ESS, but maybe with DVCC ?

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Answer 2 · 2022-10-05T08:58:27Z

nickdb answered · Oct 05, 2022 at 08:58 AM

You could enable DVCC for external control, device coordination, charge limits and shared sensors (temperature etc).

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Answer 3 · 2022-10-05T09:01:34Z

aphexer answered · Oct 05, 2022 at 09:01 AM

DVCC is already enabled, for limiting the charge current.

Shared voltage sense is enabled too, still that doesn't get both MPPT chargers to coordinate.

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ludo commented · Oct 05, 2022 at 09:06 AM

Same with ve.smart and common voltage distributed by the smartshunt.

The mppt 's ignore everything and do what they want.

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aphexer ludo commented · Oct 05, 2022 at 09:11 AM

I see, so VE.smart also doesn't synchronize the MPPT state...

Wouldn't this be a good case for a new assistant on the inverter, to control the chargers centrally? Or as an extension of the ESS assistant, to make it work with AC-in disconnected.

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Answer 4 · 2022-10-05T09:30:18Z

Alexandra answered · Oct 05, 2022 at 09:30 AM

Set the system battery monitor to the smart shunt. Is it connected to the GX?

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aphexer commented · Oct 05, 2022 at 10:22 AM

Yes the smart shunt is connected to the Venus using a VE.direct-USB cable.

In the console -> settings -> system setup -> the smartshunt is displayed under "battery monitor", so that seems to be setup correctly.

Also the configured charge current limit I've setup in DVCC is applied correctly. Both MPPT chargers together will respect it. It's just the MPPT state that isn't synchronized, one will stay in absorption or float and hardly give any power while the other one is still in bulk.

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JohnC ♦ aphexer commented · Oct 05, 2022 at 10:49 AM

Take a look at the 'Tail' function in the mppts. With DVCC they see the same V (SVS), same T (STS, so they have the same targets. And providing they have a sufficiently long Fixed or Adaptive Absorb time set, the Tail Current (SCS) can override/terminate their Absorb phase when the battery can't accept charge above the Tail setting.

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aphexer JohnC ♦ commented · Oct 05, 2022 at 05:23 PM

Thanks John! I hadn't touched the expert settings in the MPPT configuration and noticed the tail current was set to 2A on one charger and 1A on the other. I now configured it to 1A on both.

However the end-result is still the same... At the end of the day I had one charger that went into float (the 100/30 one), and the other one was still in bulk mode.

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Answer 5 · 2022-10-05T17:39:44Z

ludo answered · Oct 05, 2022 at 05:39 PM

Yes, you probably have a constant load parallel to your battery that is higher then the tail current you specified.

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aphexer commented · Oct 06, 2022 at 11:36 AM

All current goes through the smart shunt, but yes the 2 MPPT controllers + Venus consume about 1A of standby current at night and my tail current is set to 1A on both MPPT controllers now.

Why does that matter however? The MPPTs should see the current flowing into the battery from the shunt, no? Shared current sense is enabled in the DVCC settings.

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