baxter avatar image
baxter asked

ESS/DVCC MPPT not charging when CVL is reached


following Setup

-3ph Multiplus 2 5000 v494

- Cerbo GX v2.85

- AC coupled PV Fronius Symo

- MPPT RS 450/100 v1.09

- LFP with REC BMS

- ESS and DVCC enabled

- REC is providing the charge parameters

- MPPT und Multi on external control

I am observing the following behaviour that when the battery voltage reaches the CCL, the MPPTs stops charging and only the AC coupled PV Inverter provides charging via the MPs.

But this is most inefficient, there is enough sun available for the MPPT to charge.

Any ideas or advices?

Many thx!


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janieronen avatar image janieronen commented ·
Not sure what is best way but fixed similar issue by lowering multiplusses charge voltage and lifting MPPT charge voltage. Its is possible that ESS will override these settings.
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baxter avatar image baxter janieronen commented ·

As far as I understood DVCC the internal charger configuration of the MPPT and MP is not used because of external control.

The MPPT is showing external control in victron connect. The Absorption in the VRM dashboard is a bug fixed in 2.9

  • Inverter/chargers: show state as "Ext. control"; instead of Bulk or Absorption, when controlled by a BMS/DVCC. When controlled by a BMS the inverter/charger would never show float, which caused questions. Now it just shows externally controlled, simpler, and more accurate: there is no bulk -> absorption -> float charge algorithm when controlled by BMS.
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3 Answers
baxter avatar image
baxter answered ·

According to the DVCC documenation:

The internal charge algorithm is disabled; and instead, the device is being controlled by the battery.

Inverter/charger indicated charge state: Bulk when in current controlled mode, Absorption when in voltage controlled mode. Never Float; even though currents might be low / battery might be full.

MPPT indicated charge state: Ext. control.

So the question is, why is the MPPT not working in voltage controlled mode as soon as CVL is reached, but the Inverter/Charger?

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mysik avatar image
mysik answered ·

Hi @Baxter

From the screenshot it looks like you have enough power from AC side so there is no need to use DC charger, If you want your mppt to run always at max power then you need to enabled DC side grid feed-in option. On you GX device go to Settings-->ESS-->Grid feed-in--> DC-coupled PV - feed in excess <--- enable this option.

In your situation it doesn't matter if AC charge is less efficient because you have more than enough PV power than you actually need to charge your battery (on the screenshot you are exporting power 2600W back to the grid).

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baxter avatar image baxter commented ·
Sry but I do not share your opinion. Enabling DC Feed in has other drawbacks like increasing the charge voltage by 0.4V and ignoring current limit. There are good reasons why I am not enabling it.
Why wasting energy in times like this by using the inefficient way of AC/DC when there is an expensive MPPT available which can do the job, that makes no sense.

Looks more like a bug in the software that the Multiplus is priorized over the MPPT. The manual states that with current control the MPPT is priorized over inverter/charger, why is this not the case when voltage controled??

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baxter avatar image
baxter answered ·

No one? Has anyone the same setup and observing the same behaviour?

@Daniël Boekel (Victron Energy Staff) Maybe you have some technical insights why the MPPT is not priorized over the inverter/charger?


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@Baxter how could charging be faster if CVL is already reached?
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baxter avatar image baxter Daniël Boekel (Victron Energy Staff) ♦♦ commented ·

Sry I do not understand your comment? If CVL is reached the battery is still current flowing into the cells, we are in the CV part of the charge curve. This energy should be provided by the MPPTS and not the Multiplus. As you can see there are over 700Watts provided by the Multiplus and the MPPT is doing nothing.

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