New Growatt system, strange readings/behaviour at night

[Andyman75]

Hi there.

I've got a 12 panel 4kw growatt system with 3.3kwh battery.

The installation was a bit scrappy and took a good while (3+ weeks) to get the system functioning as promised, hence why I'm scrutinising the system now to ensure its working correctly.

I'm using the shinephone app to extract the actual figures from the system and noticed the system has 2 behaviours that I cannot work out what they are, I've been in touch with customer support and as yet they have not provided an answer either...
hence coming to you guys in the hope I can get some independent help and advice.

1. At any time (randomly) the system will import a small amount of power from the grid.. usually in the realm of 0.0019999
The battery can be full, I can be using virtually no power, the sun can be shining and pv providing plenty juice, but it still happens..
Then, periodically it will export the power back.. usually in the realm of also 0.001999
Or
0.0039999

Obviously it's a tiny amount, but during a day this can add up.
Which is annoying as I'm not getting any feedback tarrif as yet, so I'm paying for this trickle and getting nothing back (and even if I did, it would be a fraction of the cost to take it from them initially, so I'd rather it stopped if possible)


2. During the night, the data for pv inverter will pop up with random figures.. obviously there should be no behaviour then as no sun energy happening at 2 am.
but this usually comes in the form of readings like : 9.4E-4
8.4E-4
And also trickle power figures like :
0.00453333
0.00115
0.00284


So, that's my odd behaviour.. has anyone else had this?
Know what it is,, or more to the point how to stop it.

Can attach screen shots if needed

Thanks in advance.

Andy

 

[johnb2713]

1. At any time (randomly) the system will import a small amount of power from the grid.. usually in the realm of 0.0019999
The battery can be full, I can be using virtually no power, the sun can be shining and pv providing plenty juice, but it still happens..
Then, periodically it will export the power back.. usually in the realm of also 0.001999
Or
0.0039999

Obviously it's a tiny amount, but during a day this can add up.
Which is annoying as I'm not getting any feedback tariff as yet, so I'm paying for this trickle and getting nothing back (and even if I did, it would be a fraction of the cost to take it from them initially, so I'd rather it stopped if possible).

I'm pretty sure youre stuck with this. The inverters work by synchronising to the grid voltage. When they see power coming in to the property, they increase their output voltage until it stops. When they see power going out of the property to the grid, they reduce their voltage until it stops. Switch a load on like a kettle, the grid will supply the demand, the inverter see the import, ramp up it's output voltage until the import stops. That take a short time and you will see some import from the grid. The other point is that the output voltage isnt infinitely variable, being digital it's in steps, you may witness some import / export when cant quite hit zero in either direction

2. During the night, the data for pv inverter will pop up with random figures.. obviously there should be no behaviour then as no sun energy happening at 2 am.
but this usually comes in the form of readings like : 9.4E-4
8.4E-4
And also trickle power figures like :
0.00453333
0.00115
0.00284

I havent seen this but then again, my inverter is charging my battery at that time in the morning (00:30 to 04:30). What you will notice if it's an SPH inverter is that around sunrise and sunset, the inverter will import from the grid even though the battery has charge available. This allegedly is the inverter going through some self test routine and lasts 7 to 10 minutes.

 

[Andyman75]

I'm pretty sure youre stuck with this. The inverters work by synchronising to the grid voltage. When they see power coming in to the property, they increase their output voltage until it stops. When they see power going out of the property to the grid, they reduce their voltage until it stops. Switch a load on like a kettle, the grid will supply the demand, the inverter see the import, ramp up it's output voltage until the import stops. That take a short time and you will see some import from the grid. The other point is that the output voltage isnt infinitely variable, being digital it's in steps, you may witness some import / export when cant quite hit zero in either direction


I havent seen this but then again, my inverter is charging my battery at that time in the morning (00:30 to 04:30). What you will notice if it's an SPH inverter is that around sunrise and sunset, the inverter will import from the grid even though the battery has charge available. This allegedly is the inverter going through some self test routine and lasts 7 to 10 minutes.

Hi John,
Thanks for the reply.

To be fair, I haven't seen that behaviour with the battery in the morning..

My battery used to run out at 4am and charge from the grid then, which was simply because my overnight consumption ran it down to approx 10% .. since then I've been boxing clever with my overnight usage and can get the battery to last until about 8am before bottoming out at 10%, whereby it uses the pv to charge it back up to full with my surplus during the day, and is normally charged again by midday.

Thanks for the explanation on the trickle feeds,,, it makes sense... Let's see how long before the customer support people get back to me to tell me the same. So far it's confused them for about a week. Lol.

Again with the trickle voltage from the pv during the night,,, I could possibly pass off as test signals, also, as it doesn't affect my usage/wallet.. just with the teething issues I had initially, I'm being very diligent with my scrutiny of the system now, and am probably the most hated customer ever giving the awkward questions I'm asking, rather than just shutting up and paying. Lol

 

[johnb2713]

Have you thought about using an off peak tariff to charge the batteries? As we head into winter theres not much hope of charging it from solar.

 

[Andyman75]

Yep, agree there,,, I'm currently on a standard tarrif with octopus, but can't change yet .. As I'm still in dispute with the supplier as to whether the system is working properly because of these random unexplained readings.

As such I haven't payed the outstanding amount for the install, and they haven't released the DNO or MCS certification for me to get feedback payments or switch. Grrr.


And I'm guessing by the time this is resolved the sun will be a shadow of its former summer self. Lol
So yeah,, it's been a long road to get this far, but giving the size of investment I want to make sure it is right and working correctly.


Any suggestions on best tarrif to pick once this is sorted?

 

[johnb2713]

It wont stop you changing tariff, it will stop you signing up to an export tariff.

Most people try to get on Octopus GO, it's a EV tariff and technically you should have an EV to go on it, many people dont and Octopus dont check. The current rates are 7.5p off peak and 39p peak I believe.

J

 

[Andyman75]

Thanks John.

That's super useful to know.

So do you even bother with feedback then or just chase the late night discount which works out more economical I imagine? (certainly in winter)

 

[johnb2713]

Thanks John.

That's super useful to know.

So do you even bother with feedback then or just chase the late night discount which works out more economical I imagine? (certainly in winter)

I aim to store / use all what I generate and fill up on the off peak. The net result is all of my energy is either 7.5p or free.

 

[Andyman75]

Just checked.. need to call them to switch, but that makes total sense.
With my calculations last month (long sunny days) I was exporting average of 6kwh per day, @ what would be 7.6p if I was on feedback tariff. Which only equates to approx 48p back,, so this method is possibly more efficient than even that tariff anyway.
Hmmmm.
Some very nutritional food for thought there John.

 

[Andyman75]

I've just requested the switch.
Cheers again John for that advice..


But if anyone does have any input into the bizarre overnight pv readings I'm having I'd welcome any input.

 

[yozhughes170]

If you go onto the Go tariff then you can’t get the 7.5p export tariff with Octopus. But they have started a 4.1p tariff, but you will need your MCS & DNO approval letter. Or stay on standard tariff and get paid to export, which won’t be cost effective

 

[binky]

PV inverters do use small amounts of energy on standby, ie overnight. It's a point not often mentioned and usually in the order of about 7w. And as John mentioned above, they also communicate with apps and portals, so they have to get that energy from somewhere.

 

[Andyman75]

If you go onto the Go tariff then you can’t get the 7.5p export tariff with Octopus. But they have started a 4.1p tariff, but you will need your MCS & DNO approval letter. Or stay on standard tariff and get paid to export, which won’t be cost effective

Hmm, I wonder how many times you can switch tariff in a year?
Does anyone already have a seasonal switching habit that can confirm?

I'm certain that in winter months I'll have virtually nothing to export anyway, so the 'go' tariff seems most cost effective..

Come the summer months, it looks like I'm averaging 6.5kwh exported to the grid and no need to charge battery from grid.
Assuming 14p/kWh feedback= 91ppday. So with that assumption it would be worthwhile switching again to a feedback tarrif for summer.

I'm now signed up to the 'go' tariff, so will run with this over winter and hopefully by the time spring arrives I'll have necessary solar paperwork to change to a feedback tariff.
(But obviously these are based on current energy prices, this may yet change come Oct price hike)

 

[johnb2713]

Hmm, I wonder how many times you can switch tariff in a year?
Does anyone already have a seasonal switching habit that can confirm?

I'm certain that in winter months I'll have virtually nothing to export anyway, so the 'go' tariff seems most cost effective..

Come the summer months, it looks like I'm averaging 6.5kwh exported to the grid and no need to charge battery from grid.
Assuming 14p/kWh feedback= 91ppday. So with that assumption it would be worthwhile switching again to a feedback tarrif for summer.

I'm now signed up to the 'go' tariff, so will run with this over winter and hopefully by the time spring arrives I'll have necessary solar paperwork to change to a feedback tariff.
(But obviously these are based on current energy prices, this may yet change come Oct price hike)

In terms of switching tariffs, most suppliers have a penalty clause or a leaving fee, Octopus dont.

Agile Export seems to be the one to go for, some amazingly high prices on there bandered around - 60 to 80p kWh.

 

[yozhughes170]

Check your go tariff terms, I swapped over in July and it’s fixed until July 23, which I wasn’t aware of, result.

 

[johnb2713]

Check your go tariff terms, I swapped over in July and it’s fixed until July 23, which I wasn’t aware of, result.

Yes mine is fixed until April BUT if I wish to leave / change tariff I can do so without penalty.

 

[Slateral]

I believe you have to stay on an Octopus tariff for 30 days before changing again. Agile Export in the summer and Go in the winter sounds like a way to go.
Expecting Octopus to release their revised tariffs soon following the government’s announcement on energy tomorrow!

 

[Mizunoid]

Inverters use a tiny bit of AC to run.

 

[Andyman75]

Well, currently growatt customer service seem completely confused by my random readings overnight.. if/when I get an explanation I'll add more into the thread


Locked to prevent hi-jacking (again)