question

matthias-roetzer avatar image

feed in excess power not working in absorption phase

Hi Community,

my Question:

How can I manage to feed in excess solar power during absorption phase as well?

my system:

  • Octo GX
  • 3 pcs MultiPlus-II (3 phase connection)
  • 3 pcs DC Coupled MPPT Solar charge controller
  • 2 pcs AC inverters from SMA connected to the UPS side of the MultiPlus each per one phase (L2 and L3) but not yet measured with energy meter.
  • 48V lead GEL battery

how the system behaves, see image below

  • battery is in absorption, so DC voltage constantly 57.5V in this phase
  • AC power from SMA inverters on L2 and L3 is used to charge the battery
  • excess AC coupled PV power is feed to the grid so far so good
  • but DC coupled PV charger power is drastically reduced in order not to exceed 57.5V (in the image below reduced to 236W but often to as low as around 50W)
  • The available DC coupled PV power at the time would have been around 1.5kW
  • As soon as absorption phase is completed the DC coupled PV power goes up to the maximum as per solar input and the system starts feeding excess solar power to the grid.
  • see second image as well, this was an overall clear and sunny day. so no need to reduce solar pv power on lunch time. should be a "nice" daily full power PV curve.

My config:

  • DVCC enabled
  • SVS enabled
  • STS enabled
  • feed in excess solar power enabled
  • battery monitor is MultiPlusII on VE Bus

Best regards,
Matthias




MPPT - Solar Charge ControllerMultiplus-IIESS
2019-12-08-113610.png (115.0 KiB)
1581001462493.png (32.2 KiB)
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7 Answers
matthias-roetzer avatar image
matthias-roetzer answered ·

Hi all,

This issue was resolved by later firmware revisions.

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matthias-roetzer answered ·

I've further investigated the issue!


my GEL battery from Hoppecke has the following settings inside ESS Assistant (3xMultiplus)

float: 54,0V

Absorption 57,6V


When feed in PV excess power NOT working, the MPPTs charge voltage under "Networked Operation" is set to exactly these values!


When feed in PV excess power IS WORKING, then the MPPTs charge voltage under "Networked Operation" is set to exactly 0,4V higher than the above values, so to:

Float: 54,4V

Absortption: 58,0V


I'm not aware how I can have an influenze on these automatically set values.


I've followed som hints in the Forum not to use SVS, so I tried that, but doesn't make a difference as far as I can tell. Furthermore, I've played around more with DVCC settings bute doesn't help as well.


Please HELP - Thanks!


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matthias-roetzer avatar image
matthias-roetzer answered ·

Hi folks,

In the last weeks I came to know, that feed in of excess PV power is sometimes working and sometimes not in absorption phase. So I'm actually back where I started. Even raising the voltage levels of the MPPTs doesn't help, at least not always. It's very strange to see that feed in of PV excess power is working and then the next second is not while after a few seconds later it is good again.

Meanwhile I have updated the ESS assistans and tried RC 2.52 on the CCGX, but no improvement so far.

Any new hint is well appreciated!

Best regards,

Matthias



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matthias-roetzer avatar image
matthias-roetzer answered ·

I've raised the absorption voltage of the MPPTs from 57,6 to 58,0V while keeping the MultiPlus as Master with absorption level of 57,6V. Perfectly working now. The MPPTs try to raise the voltage above 57,6V and the Multiplus are feeding in the excees power in order to keep 57,6V in absorption phase!

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matthias-roetzer avatar image
matthias-roetzer answered ·

my current system layout:


1581063659040.png (913.3 KiB)
1 comment
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Ok, that's how I envisaged your system probably should be. It wasn't clear.

But ESS is outta my comfort zone. If it's allowing charge from both sources, try my 'quick fix' to allocate priority.

matthias-roetzer avatar image
matthias-roetzer answered ·

Hi JohnC,

That I forgot to mention I have ESS enabled, meaning the assistant installed on all Multiplus and the DC chargers show "ESS" in the display.

I've upgraded to the latest firmware which was available October 2019.



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JohnC answered ·

Hi @Matthias Roetzer

A 'quick fix' might be just to pull well back on the Multi charge settings to let the mppt's dominate. Let's say all down to a 'Storage' level of 52.8V.

Muchly dependent on what you're overall aims are, like whether you grid is up all the time, maybe using the batts as a ups backup? Perhaps tell us more..

Maybe you don't need a daily Absorb on the batts, especially twice from both chargers?

You could also look into ESS, even with your ac-coupled pv hooked to ac-out. https://www.victronenergy.com/live/ess:design-installation-manual




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