question

baxter avatar image
baxter asked

ESS/DVCC MPPT not charging when CVL is reached

Hi

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!


1660726423313.png

MPPT ControllersESSDVCC
1660726423313.png (43.9 KiB)
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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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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?

Thx!

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Daniël Boekel (Victron Energy Staff) avatar image Daniël Boekel (Victron Energy Staff) ♦♦ commented ·
@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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bjwtb avatar image
bjwtb answered ·

@Daniël Boekel (Victron Energy Staff)

@Baxter

Same here. Grid coupled Ess multiplus II with cerbo and mppt on 4x12V Lead acid

When SOC drops to minSOC because of using heavy equipment, the MPPT shuts down for no reason. Plenty of sun, console showing ESS #1 #2. SOC say 90%.

Next morning the same, SOC still 90%, no MPPT action.

Then all of a sudden SOC pops uo to 100% and everything is running again.

Earlier Cerbo didn't show this behavior, but it had a factory issue with 48V systems so it was replaced. These gremlins seem to pop up after the replacement.

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nickdb avatar image nickdb ♦♦ commented ·

You have batterylife enabled and the active limit is high so is stopping at that soc.

Do you have a shunt? If not, the SOC is probably inaccurate as an ESS doesn’t work well with the internal meter.

Disable battery life, and if you don’t have a shunt, get one. If you do, the settings sound like they need improvement.

ESS works with SOC, chargers with Voltage, if these two don’t agree conflicts will happen.

It is unrelated to this thread as you don’t have managed batteries, suggest you open a new one or do some searching as there are existing topics on this subject.

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bjwtb answered ·

@nickdb

No shunt. The system worked fine for a year until the 48V Cerbo went pop and it was replaced.

SOC changes in the blink of an eye from 90 to 100%. And that's very strange.


Searced a lot on this communuty, no specific results. No reactions whatsoever on a new thread I started, so I just hooked up on the closest to get response.


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nickdb avatar image nickdb ♦♦ commented ·
Maybe not all settings were put back, but in an ESS, SOC will be off on a solely internal meter as it can't measure the MPPT charge and has to estimate it. So shunts are a requirement for an accurate SOC.

As mentioned, traditional batteries don't send a CVL as they aren't smart and there is no BMS, so this topic won't be overly helpful.

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lucca371 avatar image
lucca371 answered ·

On my ESS system with DC coupled excess feed, my MPPT's also regulate the power down when the battery is full.
The MPPT's are on external control and everything is controlled by the BMS via DVCC (CVL=55.2V).
It is noticeable that the regulation only takes place when the BMS comes with CCL=0A. Then the DC voltage quickly fluctuates back and forth in the range of 53-55V. One MPPT is limited to 0W and the other runs at low power. At this moment, the LEDs bulk and float flash alternately.

When CCL>0A the MPPT'S work at full power and the voltage is constant (+-0.0xV).

When I set the managed battery voltage to 54.4V with DVCC, the CCL is always >0A and the MPPT's work at full power (54,6V dosnt work). The voltage is then constant between 54.40 and 54.46V.
At 54.4V the battery (Gobel Power GP-SR1-RN150) is charged to 100% and the BMS always supplies CCL>0A.

I don't know the reason for this behavior. In another system with Pylontech, the MPPT'S worked at full power when CCL=0A. There is also no voltage limit set for DVCC.

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