New Member

[power]

Hi everybody , my name is Carl

I have just had Solar PV, Growatt SPH500 Hybrid Inverter , 2 * 6.5 kWH batteries and Myenergi Eddi installed.
I have been monitoring the system for 2 weeks now and have noticed , as others have mentioned on this forum, that there is a continuous small import (0.01-2 kWH) from the grid even when the batteries are full except when exporting to the grid.



Similarly the inverter is drawing from the battery to export to the grid without any instruction to do so



Why is the inverter not withdrawing only 0.01kWH from the batteries to match the load?

I have read elsewhere that CT clamps are inaccurate and that replacing them with an energy meter may be a solution. Does anyone her have any experience with resolving this issue ?

 

[Murdoch]

Is a minute draw from the grid a problem ?

what do the suppliers say ?

 

[johnb2713]

The inverter changes it's output voltage to have control of import and export. Being digital, the change in voltage is done with a finite number of steps, so for example, if the voltage was set and a slight import was still occuring, the next step increase may cause export to happen, it is entirely possible the inverted can achieve the exact voltage needed for no import / export.
With reference to CT's, they are a transformer with a single wire as the primary, the higher the current is the meter tail, the stronger the magnetic field and therefore the voltage induced into the secondary and on to your inverter. As the currents reduce, the output voltage also reduces, as it gets really low the noise on the signal line becomes equal to or greater than the signal itself and thats when we have a problem. CT's at low current levels are useless, a meter is much better. The problem with meters is that they take time to convert the analogue signal to digital numbers, it then takes time to transmit the numbers and for the inverter to receive them using the data accordingly. Meters are very good from an accuracy point of view, even at zero but their response time is poor.

Your figures in all honesty don't look too bad, I personally wouldnt worry too much. A much bigger issue is around sunrise and sunset when the Growatt's import from the grid even though there is energy in battery that could be used.

 

[power]

Thanks John your reply was very informative. My average import is 0.8kWH per day which roughly equates to about £96 per year (@ 33p/kWH). This does seem to be an unnecessary overhead as there is plenty of battery power available.

​

 

[binky]

Thanks John your reply was very informative. My average import is 0.8kWH per day which roughly equates to about £96 per year (@ 33p/kWH). This does seem to be an unnecessary overhead as there is plenty of battery power available.

​

But how much are you saving?

 

[johnb2713]

Thanks John your reply was very informative. My average import is 0.8kWH per day which roughly equates to about £96 per year (@ 33p/kWH). This does seem to be an unnecessary overhead as there is plenty of battery power available.

​

You could try a meter in place of the CT, that may improve things at the low import / export levels but it may be at a cost in response times to a step change in load eg and immersion heater switch on/off. It is possible that youre in the zone of operation where the steps in voltage arent fine enough to really trim the import / export to zero. To truly get away from this situation, remove the grid tie and run your load from the inverter directly, importing from the grid to charge batteries only if necessary.

 

[power]

I have checked the numbers since installation and you are correct that the cost of the import is marginal w.r.t the savings and potential income from export. I currently do not have an export mpan and so am not earning anything from exports at present.

For info

kWH	Solar	Grid	Load	Self	Export
09/05/2023​	7.5​	0.4​	7.5​	7.1​	0.4​
10/05/2023​	26.6​	0.5​	10.7​	10.2​	16.4​
11/05/2023​	25.4​	0.5​	11.3​	10.8​	14.6​
12/05/2023​	6.8​	0.3​	6.9​	6.6​	0.2​
13/05/2023​	5.6​	1.4​	6.7​	5.3​	0.3​
14/05/2023​	15.4​	0.3​	6.9​	6.6​	8.8​
15/05/2023​	23.2​	0.5​	8.7​	8.2​	15​
16/05/2023​	30.6​	0.4​	12.1​	11.7​	18.9​
17/05/2023​	20.7​	0.4​	8.7​	8.3​	12.4​
18/05/2023​	21.3​	0.5​	7.6​	7.1​	14.2​
19/05/2023​	7.3​	0.4​	5.5​	5.1​	2.2​
20/05/2023​	26.3​	0.8​	9.6​	8.8​	17.5​
21/05/2023​	30.8​	0.5​	7.7​	7.2​	23.6​
22/05/2023​	7.6​	0.4​	7.8​	7.4​	0.2​
23/05/2023​	18.9​	0.4​	8.9​	8.5​	10.4​
24/05/2023​	28.9​	0.5​	8.4​	7.9​	21​
25/05/2023​	18.1​	0.5​	7.5​	7​	11.1​
26/05/2023​
27/05/2023​
28/05/2023​
29/05/2023​
30/05/2023​
31/05/2023​
		Cost	Saving		Potential Income
Total kWH	321​	8.7​	142.5​	133.8​	187.2​		Export Rates
Value GBP		2.96​	48.42​	45.47​	30.11​	Low Rate	0.2298​
					20.54​	Peak Rate	0.3658​
					50.65​
Actual Saving	45.46​
Potential Gain	96.11​