Solar PV questions from a newbie...

Officer_Dibble

Hello all. Very excited to have turned the roof into a power station. My dad used to help run a real one, I've finally caught up with the family profession. OK, his had 250GW capacity, mine has 4.7kW, but you've got to start somewhere.

Obsessively watching the output of the system between juggling loads of washing/immersion boosts/letting the cat having a little free electric heating boost (I hope the obsession will reduce after a few days, I can't keep it up), I noticed a sudden drop-off without a cloud in sight. We'd been merrily chugging along at about 4.3kW for a decent time, then it dropped to 3.9kW and stuck there. Does that sound like a panel suddenly stopping working, or is it just the sort of thing that happens and I shouldn't worry? They're all on optimisers.

I'd been expecting a maximum output from the battery of 3.6kW, but it doesn't seem to every get above 3kW. I wondered if it had all been wired out of the EPS output, but it doesn't look like it. Could it be a setup issue, or is that all I should expect?

Thinking of EPS, the quote mentioned "1 x Emergency power back up supply", but the EPS output doesn't appear to be going anywhere. Am I right that this implies that in the event of a power cut, there'd be no output from the battery? It sounds like a considerable amount of wiring to change that, and the very reasonable install cost certainly didn't cover a considerable amount of wiring. Perhaps the quote just refers to a facility that could be used potentially...but isn't.

Obviously these are all things I can talk to the installer about, but I'd welcome any insights before I do.

Thanks!

ps - scraped my first Hawaii today - 5.02. The cat's enjoyed the extra heat, as I can't sell it back to the grid yet.

Officer_Dibble

Just trying to find my way around the not-to-pleasant Growatt app, the Inverter power does seem to make it up to 3.6kW, it's the battery discharge that seems to stick at 3kW. It looks like it might be a "feature" rather than a fault.

NoobSolar

I don't know the answer to your question, but can I ask what it is you're heating with that electricity which the cat is enjoying? Does the house have an electric heating system? I have an iboost for the hot water cylinder. I wish something similar existed for a normal radiator central heating system.

Officer_Dibble

Hi (other) NoobSolar - nothing complicated, just an old Delonghi convector heater with a fan - actually one that the previous owners had left behind and we'd hardly used until now. Sends a nice warm draught over the cat and fluffs him up nicely. I might need to plug it into a smart plug so I can switch it on for him when we're out. I just need someone to write an IFTTT app - if it's sunny but cold, turn on socket (and find cat and put him in the right place).

I didn't go the iBoost route as I was worried about it fighting the battery, but got a wifi fused spur to switch the immersion on easily and remotely if there's spare power. Again, it could do with a sunlight related automated switch. It's probably really easy if I knew how!

Solarchaser

If the growatt is an sph3600 then 3kw is indeed its max for the battery. Somewhat deceiving in the blurb, but the datasheet reveals all.


Regarding the solar output, that's actually a bit of an issue.
You see a 3600 inverter is specced that way to export that as a maximum to the grid, so it shouldn't be able to export more.
However mine when I had it would export over 5kw which was a safety issue, as the wiring was specced for 3.6kw

Growatt were less than helpful and after threatening them with court, I was eventually refunded.

Having an eps function and having that function wired up are indeed two different things I'm afraid. 

Any possibility of getting the inverter changed for a non growatt?

You have a new addiction,  it's something a few of us have, id like to say you will get over it, but I've been over 3 years with solar+batts and still check the app more than once a day.

Officer_Dibble

Thanks Solarchaser - it is indeed a SPH3600, and you're right it is somewhat buried in the smallprint. Shouldn't prove too much of an issue, just means importing a bit while the kettle's on if there's no sunshine at the time. There seem to be an infinite number of parameters that can be changed, I'm surprised that limiting the export to 3.6kW isn't one of them.

I presume there'd be a significant extra cost for swapping out the Growatt. It seems to do roughly what it should and provides me with a few hilarious mistranslations to brighten things up, so I'll stick with it. It'll be cheaper just to get a less powerful kettle!

Officer_Dibble

I've managed to make a sequematic sequence to turn the immersion on for an hour at lunchtime if cloud cover's low. Now for the warm-up-the-cat sequence..

Magnitio

Officer_Dibble said:

 I noticed a sudden drop-off without a cloud in sight. We'd been merrily chugging along at about 4.3kW for a decent time, then it dropped to 3.9kW and stuck there. Does that sound like a panel suddenly stopping working, or is it just the sort of thing that happens and I shouldn't worry? They're all on optimisers.

When your output dropped from 4.3 to 3.9, what was the state of charge for the batteries? Your inverter has a max AC output of 3.68kw, so any excess generation is either for charging the battery or is lost. Therefore, as your battery approaches max state of charge, the output will start to drop towards 3.68kw.

Alternatively, it could just be the time of day and angle of the sun hitting the panels.

mickyduck55

Officer_Dibble said:

It'll be cheaper just to get a less powerful kettle!

I have a 2kWh kettle thoroughly recommend getting one.. Its one item that is on and off many times everyday without being able to schedule so having a lower power unit does keep my draw from the grid very low

paul991

i  would recommend a neostar  boils on 600w and 100 w keep  ready  mode so can  be used on longer time frame without drawing from grid 

Officer_Dibble

Thanks for the kettle recommendations, I'll do some research - the neostar permatherm looks ideal at a glance.

The panels have generated over 5kW on a couple of occasions between clouds today, so it looks like they're all working. Could have been a battery filling thing as Magnitio suggests. Can a 390W panel ever produce more than 390W, or is there some reporting error somewhere?