Am I doing something wrong?

[jonmjones]

I have a 22 panel equal EW strings, H3-10 and EP11 battery (Three Phase).

I notice that as soon as the PV volts are 0, the battery stops DISCHARGING and starts topping itself up from the grid. I have the app set to Self Use and tried a few schedules, most recent being:

Midnight-23:59
Self-Use
Min SoC on grid 10%
Max SoC 10%
FDSOC 10%
FDPwr 10000W

Am I doing something dumb?

I've had the system a week and installer unable to get his head around the problem. Fox support being quite useless too.

I also notice, for example now at 10:15pm, Load, Grid PV and Battery all showing 0w usage. Battery is 100%. Sometimes load is a negative number too.

My aim is to use PV and battery and only buy from grid when battery is 10%. Battery to only be charged from PV (although will use cheap grid once our energy supplier switch is sorted).

[Dave Foster]

That sounds very much like the installer has wired 1 or more of the phase incorrectly at the meter.

Being 3 phase your have L1/2/3 and these must be maintained throughout the system and particularly at the inverters meter (or it may be a meter with CT clamps in which case a clamp may be reversed) - but if you have phases swapped the inverter sees a load on a phase and responds on that phase - because the meter is wired wrong the inverters response is on the wrong phase and so you’ll see a negative load being reported.
Likewise it will get it’s metrics wrong and not use the battery properly discharging and charging incorrectly as you are seeing.

It’s a subtle fault and needs the phase wiring to be checked so that what the inverter is measuring as L1 is the correct way round and reading the correct L1 phase, rinse and repeat for L2 & L3.

[jonmjones]

I think thats a very good shout, thanks.

[jonmjones]

That sounds very much like the installer has wired 1 or more of the phase incorrectly at the meter.

Being 3 phase your have L1/2/3 and these must be maintained throughout the system and particularly at the inverters meter (or it may be a meter with CT clamps in which case a clamp may be reversed) - but if you have phases swapped the inverter sees a load on a phase and responds on that phase - because the meter is wired wrong the inverters response is on the wrong phase and so you’ll see a negative load being reported.
Likewise it will get it’s metrics wrong and not use the battery properly discharging and charging incorrectly as you are seeing.

It’s a subtle fault and needs the phase wiring to be checked so that what the inverter is measuring as L1 is the correct way round and reading the correct L1 phase, rinse and repeat for L2 & L3.

So, been back and forth with installer and them with Fox support. They say its normal what I'm experiencing, and even that the battery wont be used to cover base load over night as it's too small (100-300w).

* We were on the grid overnight
* As soon as there was voltage on the PV, the inverter switched over to the battery
* The battery discharge went down as the PV power went up to fill the gap with the load
* PV took over 100% once there was more than enough to sustain the load during peak daylight
* As the PV power went down at the end of the day, the battery discharged again to offset the load (but was being trickle charged by grid)
* When the PV finally had no voltage, the inverter switched from the battery back to the grid
* The battery charged from the grid

During this,

* I noticed the load, grid and battery figures were all not correct vs what Octopus and smart meter report.
* I noticed the amount the battery is being charged appeared to be what the inverter thought the load plus export to grid was.
* This also correlated with the live smart meter (octopus reading) which are showing import during most of the day but more overnight corelating to our load plus the amount the battery needed to top up to 100%.

[EcoByte]

I have a similar setup with 3 phase, EP11 and Fox inverter. What you describe sounds wrong. My setup during June, for example, cost me about 85p per day inc standing charge. I set the usage as Feed-in first and disabled the battery during the off peak hours of Intelligent Go. All other times the battery dealt with the house load and was not charged by the grid for several days. The grid supplied the heat pump overnight to heat the hot water.

I'm not technical enough to suggest what may be wrong, but what you're being told by your installer and Fox doesn't fit with how my setup operates. Hope that is of some help.

[Dave Foster]

So, been back and forth with installer and them with Fox support. They say its normal what I'm experiencing, and even that the battery wont be used to cover base load over night as it's too small (100-300w).

* We were on the grid overnight
* As soon as there was voltage on the PV, the inverter switched over to the battery
* The battery discharge went down as the PV power went up to fill the gap with the load
* PV took over 100% once there was more than enough to sustain the load during peak daylight
* As the PV power went down at the end of the day, the battery discharged again to offset the load (but was being trickle charged by grid)
* When the PV finally had no voltage, the inverter switched from the battery back to the grid
* The battery charged from the grid

During this,

* I noticed the load, grid and battery figures were all not correct vs what Octopus and smart meter report.
* I noticed the amount the battery is being charged appeared to be what the inverter thought the load plus export to grid was.
* This also correlated with the live smart meter (octopus reading) which are showing import during most of the day but more overnight corelating to our load plus the amount the battery needed to top up to 100%.

It's confusing and i'd really need to look at your load, grid consumption, battery charge/discharge stats to understand better - but one thing i'm wondering, is this the standby usage of your inverter and not just the house base load.

A large 3 phase inverter consumes energy to keep running overnight this should come from the battery but the bias is from the grid so there will be some power being drawn from the grid - i've heard of figures as high as 150 watts but never 300 watts. It isn't just base load, it's the power needed to keep the inverter, batteries and BMS running. But if that were the case I would expect they might offer to set the grid compensation to compensate - the grid compensation sets the bias point so that a little bit of power is pushed back to the grid to compensate for this leakage.

Also just thinking about what @ecobyte has said, try setting your inverter to feed-in workmode over night and see whether there is any improvement in this leakage. Feed-in changes the inverters bias point towards the grid, so it's possible you will see a reduction in usage in this mode.

[jonmjones]

Thanks both, will try that setting.

I'm very new to all this and the sale person made it sound like I'd have zero bills other than standing charge while the battery had power remaining.

The laggy app also makes it very hard to monitor in my opinion. Is there a better way?

e.g. if i boil the kettle at 10pm, I'd expect the battery to peak at approx kW the kettle is drawing but by the time the app updates, it's too late!

[EcoByte]

I wondered about testing the battery usage with a high load when it was dark, but the 5 min polling interval of the software is a pain. The app shows updated x min ago, but the Energy Stats app does better and gives a next update in x min x secs. Or you could try the immersion heater if you have one and monitor the load over a 5 min interval. The web app should give you a discharge peak on the graph for the heavy load.

[jonmjones]

Is this a clue, look at the load and grid while it's discharging. My home is using barely any power right now, just fridge, wifi etc.

An recharging seems to make load negative, and octopus says we are pulling constant 500w from the grid, which equates to the difference between the PV and negative grid....

[Dave Foster]

I’m still going to go with what I said before, one of the meter phases is reading incorrectly - going to need to dig much deeper.

If you swipe left on that screen can you screen shot the graph and battery soc towards the bottom of that page.

Also need you to log into the www.foxesscloud.com website, click on Device on the left Menu and choose Inverter, then click the icon on the right hand side underneath ‘operation’

Scroll to the bottom of that page and you will find a blank graph, in the drop down select these items RPower,SPower,TPower and search - can you screen shot that graph.

Then clear those 3 selections and select LoadRPower, LoadSPower, LoadTPower and search - screen shot that graph

Finally clear those 3 selections and select MeterRPower, MeterSPower, MeterTPower and search - screen shot that graph.

If you can post those screen shots it might help work out what is happening and on which phases.

[jonmjones]

[Dave Foster]

Just to clarify for me, it looks like you set the inverter to Force Discharge at full power and you can see the R/S/TPower shows that each phase is outputting 3.39kW which is what you would expect.

The problem then is that the power measured by the meter for each phase is lower on 2 phases and much lower on the RPower - that suggests a load is taking the difference so that would be approx 1.3kW on T phase, 0.8kW on S phase and 2.7kW on R phase - which would show a combined load of around 4.8kW, but there was no load on in the house ?

And also to check you don’t have anything like an iBoost on your hot water (or similar) that kicks in to use excess solar (force discharge is seen by them as PV export).

Could you grab a couple of pictures of your meter cupboard, if there are any CT clamps could you get close ups - I may need a few but i’m now sure what i’m looking at yet, probably know more when I see them.

EDIT: Sorry should have asked, do you have any independent way of checking how much power you are importing or exporting per phase - does octopus smart meter show that ?

[jonmjones]

Correct about the force discharge at 4pm. Just a trial to test it worked.

We have no iboost or device that soaks up any spare pv.

Right now we have no export as tariff still being set up, but grid meter shows 208 vs 143 that fox app reckons. Unfortunately I cannot tell per phase.

Couple pics here. Hard to get a decent angle as buried in a cupboard! The arrows point at the consumer unit.

[Dave Foster]

Ok it looks to me like there is a problem, without measurements it’s difficult to identify it and i’m guessing you will need to do some testing to see explain to your installer what it is.

Do you know what appliances you have on each of the phases - really need to get methodical and trigger a good sized load (pref 1-2kW) like a full kettle or an oven, electric radiator etc.. ideally on each phase and leave it for 5 minutes to allow the data sample to be taken and see what the effect is on the Loads & meter R/S/T phases.

As this install is using CT clamps it is possible they have entered the wrong transformer ratio in the meter so when you are taking 3kW, the CT’s / meter is only measuring 2kW (you can see that above) - that could be why it’s only showing a 2kW export per phase when it knows it is delivering 3.39kW per phase and so it calculates the rest is being taken by a load.

In an ideal world what you need is to identify when a fixed load is presented on a phase, how that phase measures the load and what the effect is on other inverter phases. - the measurement will show that the transformer ratio is correct in the Chint meter, the effect on the other inverter phases will show whether they are being measured correctly i.e. L1=R, L2=S, L3=T - I would say your installer should be doing these checks, but if you can at least demonstrate a problem to them it’s easier to solve.

[jonmjones]

Thanks for your continued help, I’ll find a fan heater or something with a chunky load and do what you say so we have data when then installer returns.

Is what they say about not being able to use the battery overnight when load is low true? In my mind that defeats the purpose of having the battery. We are still consuming approx 5kWh during dark hours in total which seems a lot to not be able to offset with free energy sitting in the battery.

[Dave Foster]

Thanks for your continued help, I’ll find a fan heater or something with a chunky load and do what you say so we have data when then installer returns.

Ok great, make sure you keep a good record of what you did and give it maybe 10 minutes for the test and between the tests so that the data samples have chance to get to the cloud.
Please post the screen shots of the RPower R/S/T, Load R/S/T and Meter R/S/T for me to have a look at.

Is what they say about not being able to use the battery overnight when load is low true? In my mind that defeats the purpose of having the battery. We are still consuming approx 5kWh during dark hours in total which seems a lot to not be able to offset with free energy sitting in the battery.

The battery will be used to meet the loads overnight even if they are small, the confusion is as I mentioned before the inverter / batteries consumer some power to run overnight but no more than 2 - 3kW a day (max), and that should be able to be reduced further by setting the grid compensation setting, not zero but less than 1kW.

[jonmjones]

The installer has moved the meter closer to the grid meter (it was 30m away before). It seems to have resolved the issue!

Happy bunny now!