PV comes on 5 min after frequency shift

Q&A and troubleshooting
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1

Hi all,

I have 2 x 5000 Multis, Cerbo, power monitor and a non-victron 51.2 Volt LFP battery.

When the grid is off and the battery is full, I set ip up that the frequency shifts and shuts off the charging.

And I set it, that it starts charging again, when the voltage is down to 54V again from the full voltage of 57.5V

The thing is that the system only waits the typical Enphase 5 minutes and then starts charging again.

It ignores the fact, that I want the voltage to go more down. Right now we have full sun and the Battery is full in a few minutes again, because the house uses only around 500 Watts and the whole process starts repeating itself.

I tried the PV inverter assistant and also the ESS assistant. No luck on both. The same outcome.
Any suggestions what I can change in the PV-inverter or ESS settings?

2

Can you set a lower voltage for the Charging restart?

3

I did. Set it to 53V. But the PV comes on again way above that.

Mostly at around 54.3V

4

ok, but why worry? If this keeps the battery between 80 - 98%, there is no issue with Lithium shallow cycling at this level.

5

The battery voltage setting is just a minimum value to force acpv recovery “at latest”.

Whenever there is consumption, the system will try to unthrottle as much acpv as there is consumption.

The Issue is most likely that the enphase inverters do not act as they should, a lot of micro inverters only support 50% power as their minimum output.

So, whenever the system is lowering the frequency, to a value that should allow like 5% power generation, the enphase may just ramp up to 50%. (Or any other internal minimum)

I don’t know how much enphase power you have, but if not all too much, you could resolve this by adding a remote controllable switch like a shelly, turn off at 98% soc, turn on when down to 90% or whatever values you desire.

For higher power systems you would need a bigger relay / magnetic switch that is suitable for the maximum power rating.

6

Lol, yes. But this happened every 5 minutes an I am not sure if some components do not like it.

The battery does not even go down to 99% . . .

Btw. how can I upload a screen shot with the ESS settings here?

Ops, that was for Mike.

7

image
To upload an image or file, just click the upload icon in the edit box.
With solid state switching, there should be no reliability issues from cycling every few minutes. There will be more thermal cycling stress on some devices, but again, this should not be too much of an issue. Better to see if you can get a slope regulation scheme to work, such that the inverter reduces it’s power rather than shutting off completely. Typically this is done with the PV inverter assistant and configure 100% at 51Hz 0% at 52Hz and cut off at 52.5 - 53Hz (for 50 Hz system). you need to set this in both the inverter and the PV assistant. This may mean setting the inverter to an off grid standard.

8

Thanks doghouse,

I have 6.6kW of PV and a bright blue sky right now in the afternoon. The system is still charging with around 5000 Watts, meaning the battery bank is full in 1 or 2 minutes again.

I don’t know anything about the shelly switch. That sounds like an interesting solution. Can you please elaborate on this a bit?

9

since I have 60hz in the US the numbers are different but similar.

I asked Enphase about the frequency shifting and they recommended ramping up from 61.2hz to 62

I can only put in 3 numbers at the ESS. So my frequency shifting starts at 61.2, then 61.6 and finally 62

The thing is, that it shuts off at around 60.7, whatever numbers I put in there . . .

10

ESS 12-23-25
ESS 12-23-251208Ă—1278 46.5 KB

11

For 6.6 kW that wont fit. Shellies are up to 16A mostly, some just 10A. (They are basically tiny iot switches, great eco system and huge diversity, also available for wifi, zigbee, bluetooth…)

So, in your case you would need a more sturdy magnetic switch to “disconnect” the enphases from grid when you don’t want PV production above a certain soc.

But first step would probably be: Check if the enphase have some sort of API, where you can send limits to them. Then, with the venus large image and nodered you could quite easy adjust that limit based on soc to match your needs.

12

One more info: the house uses right now max 500W, and the PV system is just too big to go down that much

13

One thing to Note: PV assistant must be loaded LAST in the configuration setup to work properly.
It should also be possible to modify the enphase set up to be 0% at 60.7Hz, and 100% at 60.2Hz.

14

Have been reading about the “large image” and Node Red thing, but probably have to dig into this.:disguised_face:

As for the Shellies, my system is split into 2 arrays. So about 15A max per array (240V split system)

15

Hmm,

I had the PV Inverter assistant running a while ago and had the same problem. Then I switched to the ESS assistant and no luck either.

Can I have both running the same time? I think I saw a pop up window during the ESS setup stating that I have to delete the PV inverter assistant before I can setup the ESS assistant.

16

Yes, you need both running at the same time.

This is why the PV assistant has to be loaded last.

17

Ahh, got ya.

Always learning . . .:grin:

19

I can try that too.

60.2 then maybe 60.4 and finally 60.7

But I doubt that the micros can just put out a few watts. Even when it goes down to 50% like dognose pointed out, that is still way more than the house uses during the day.

20

Either load ESS or PV Assistant. ESS included the PV assistant allready.

The specific Hz values depend on your grid code.
E.g. CA21 (California) starts throttling above 60.4 Hz and end at 62Hz.
Though for CA21 I recommend the three values.
60.5Hz start
62,0Hz end
63,0Hz save disconnect

1 Like
21

You can disconnect 15A with a Shelly 1pm.
Or you use a Shell Pro 4pm which can switch 4x 16 with max sum of 40A. This gives you Ethernet, DIN rail, display, switches and two free relays e.g. for water heater.