New install not behaving correctly (low export, low generation)

[ptinkler]

Hello! I've recently had a new install fitted:

Apologies for using an image but I wasn't sure which the relevant model numbers etc were. I was already with octopus energy (in the UK) and I switched over to their flux tariff which is now all set up correctly and should be allowing me to export.

I had issues that seemed to start a couple of days after the install: in the app the load on the house dropped to 0 at all times (obviously not accurate) and the PV generation stayed at 0 too, it even claimed grid usage was 0. Getting support from the installer was a giant pain and took a long time, will spare the details there but a non technical person came out- saw a breaker had been tripped, flipped it back, restarted the inverter and things SEEMED to be working again (though the numbers didn't look right to me) that was irrelevant anyway because 40 minutes after he left the system went back to its zero state. I checked the breaker but it had not tripped this time, restarted the inverter myself, got another 40 minutes - an hour of life but then it went off again so I stopped restarting it and just let it be.

cut to a month later an actual electrician came out, looked at it for 5 minutes and said it hadn't been set up to be in CT mode, and after that visit things seemed to be working again as they had for the first 2/3 days (my pet theory is that it was set up correctly initially, something caused a breaker to trip which reset the inverter back to a non-CT mode- but I could be way off there), PV generation started up again, would charge the battery in the morning the house load looked accurate, I even saw export numbers.

The issue I'm having now is that to my mind, the export numbers look extremely low and generation to match. It was beautifully sunny this morning, and the graph initially shows PV generation of 1.85kwh, most of which was going to charge the battery, the leftover dealing with the house load and a small amount of export (~0.2kwh). The issue appears to be that once the battery reaches 100% SOC, the PV generation plummets, back to a value (~0.4kwh) that's suspiciously close to just the sum of the load + minuscule amount of exporting. It was still extremely sunny out and even with it being UK winter/spring with a nice south facing roof I would expect to see more PV generation than that. Occasionally the PV generation would drop to 0 and it would start using the battery, then PV kicks in again, charges up the battery once more, then goes off again in a strange cycle.

From the reading I've done here it seems like the inverter has to account for every single watt generated so I guess it makes sense that if i wasn't able to export, the battery is full, the load is covered it would dial back the PV generation to just cover that off. But I should be able to export everything I'm not using so I don't understand why it keeps maxing out at about 0.25kwh export. and dialing down the generation to match it.

I will update with screenshots of the graphs when ive uploaded them:

If this is normal behaviour then that's fine, I don't THINK cloud cover came along and coincided with my battery hitting 100% but it could all be a giant coincidence I guess. Any other graphs/timelines that would be helpful let me know

[Dave Foster]

Hmmm not a good start, it is very possible the CT clamp was not enabled from the initial install - but it is a possibility that when first installed and if the firmware is upgraded it can sometimes lose that setting.

Back to your problem, it sounds as if an export power limit has been set which is throttling the PV - basically the export limit allows you to set a lower limit than the inverters normal rating (in case your DNO specifies a low G99 limit).

You can find that setting in the Inverter Settings, and from the main panel click Settings, (password is 0,0,0,0) On-Grid, Export Control and it should be set to 60,000 (sixty thousand) which means export at the full inverters power. If your G99 specifies a lower limit you can enter that instead so for example if it were 4000 watts, change it to 4000.

[ptinkler]

Hmmm not a good start, it is very possible the CT clamp was not enabled from the initial install - but it is a possibility that when first installed and if the firmware is upgraded it can sometimes lose that setting.

Back to your problem, it sounds as if an export power limit has been set which is throttling the PV - basically the export limit allows you to set a lower limit than the inverters normal rating (in case your DNO specifies a low G99 limit).

You can find that setting in the Inverter Settings, and from the main panel click Settings, (password is 0,0,0,0) On-Grid, Export Control and it should be set to 60,000 (sixty thousand) which means export at the full inverters power. If your G99 specifies a lower limit you can enter that instead so for example if it were 4000 watts, change it to 4000.

Thanks for the response! I had a look at Export Control this morning and it's displaying 60,000. There was nothing in the letter from the DNO that suggested there was a limit so I should be ok on that front. When I got up this morning and there was virtually no load on the house, the panels were generating ~1.4kwh and this was on an overcast morning so I'm positive that they CAN be generating higher numbers. Oddly as soon as load starts going through the house the generation seemed to fall. Maybe it got more overcast? It's so hard to tell what a reasonable amount of generation to expect is.

I notice my panels are divided into two banks: PV1/PV2. I have 10 panels so is it reasonable to expect that these are 2 banks of 5? If so one of them appears to be turned off a lot of the time if not all the time, I can't remember ever seeing an equal generation number along side it. Screenshots attached

[ptinkler]

Safe to say something still seems very off about this, will switch to using the cloud site for screenshots as it's simpler but again today, sunny morning with zero cloud cover was netting me 1.5kwh until the battery fully charged at which point it has dropped to 0.4kwh despite the weather not changing. If i put a higher load on the house of ~0.6kwh it starts importing electricity from the grid to cover the shortfall and not just allowing the PV to generate more power. I will get back onto the installer about this as clearly something is not set up correctly but in the meantime is there any settings I can look at to give them a hint where to look? This forum seems considerably more knowledgeable and eager to help than the installer

[Dave Foster]

It looks like you only have a single PV string, the voltage is correct for 10 panels - PV2 is just picking up floating voltage it isn’t connected.

Yes agree something is not correct, it’s most likely the CT clamp is located in the wrong location/cable - it should be on the live feed coming from your suppliers meter. A negative load is very indicative of that, you shouldn’t see that go negative - if it is going negative it is misreading and all of the balancing logic it does to meet the load from batteries won’t work correctly.

[ptinkler]

I've attached an image of the meter cabinet- I don't know the first thing about what I'm looking at but the clamp (white box?) looks to be clipped onto the live wire... there's just an isolator between it and the suppliers meter- could that be an issue?

[Dave Foster]

As a rule that appears to be in the correct position, can you identify where the brown/blue cables are going bottom left hand corner entering the white silicon sealant, and also behind it there are a pair of grey wires - are they heading towards your consumer unit.

Assuming it is wired correctly the inverter is behaving as if it has an export limit set - just for completeness, what are you minsoc and ‘minsoc on grid’ (battery reserve) set to - and do you have either of the 2 charge periods set, or any schedules enabled.

If you use the V2 app click ‘Device’ at the bottom, ‘Battery’ at the top scroll up the page and post a screenshot of the Settings from Force Time Charge to Mode Scheduler at the bottom.

[ptinkler]

attached image, i'm fairly certain they're the defaults I haven't really touched any settings as of yet

(possibly unrelated, possibly not- is that the maximum rate the battery can discharge? because the load on the house is currently ~0.5 and it only seems capable of discharging at ~0.4 so I have to import energy from the grid at peak time

[Dave Foster]

The settings look ok, the charge power is how much power the battery is giving up - it should comfortably meet your house power at those loads.

You can see what the maximum allowable is from the BMS by clicking Device, Inverter, Detailed Parameters, Battery Information and scroll down to the bottom - the max discharge / charge rates change depending on soc, temperature etc.. that is the maximum power the BMS will allow.

But there is also the Inverter maximum discharge current setting - you can check that at the Inverter panel Settings, Battery, Max Discharge Current and it should be set to 40A for your inverter.

[ptinkler]

it looks normal, i can check on the inverter screen itself if its possible to be a data display error in the app. at this point i think i need to go back and make more noise with the installer because really they should be the ones putting the time in to make sure this works 100%, given the cost!

[Dave Foster]

Do check the inverter the BMS and the inverter maintain separate values - the inverter sets the normal rate and the BMS the max allowable rate - the lowest one wins.

[ptinkler]

I had a look on the inverter panel screen and max charging/discharging were both set to 35A, i set the discharging to 40A and it seems to be discharging at .45kwh, with the oven and hob on there's a load of 2.3kwh so 0.45 seems to be the max it will do (might be a bit cold, 7.5C battery temp as its an outdoors install. I realise I forgot to mention that so hopefully that isn't the cause of any of this!).

either way, I have emailed the installers again and will phone tomorrow and relay all this. thanks very much for the help!

[Dave Foster]

Temperature will be playing a part, it looks like you only have 2 batteries ECS2900? - a stack of 2 has a nominal voltage of 115v so at maximum performance (25C) they should supply 4.6kW but if it’s 7.5C that will likely be reduced to around 1kW.

Updating the firmware on both inverter and batteries would be a good first step, the cold may have an affect on your batteries but that died t explain your PV is being limited rather than being exported - let us know how you get on