Is my system working correctly?

[MrTWales]

Hi all - I've had my system since 25 October, and with all the sun this week I've been looking at the figures. I get that you always get small imports from the grid, even if it in theory doesn't need to happen (as the battery + solar have enough power), but today the figures look odd.

 

The data as per the snip suggest that I've imported 1kw today, but there has been lots of solar and the battery is almost full. This looks like it was mostly between 2pm and 3pm when I was cooking, but shouldn't the battery have been used then?

 

Can I also check my understanding of the figures that the inverter produces: I'm assuming that the generation will be correct (as everything flows through the inverter), the battery figures are probably accurate, but all others are only estimates? It beats me how the inverter knows if I'm using a hair dryer in a bedroom as it's in a garden room, but it seems to have some idea. The inverter figures don't quite add up in that they say: solar 407, import 669 and consumption 1003. Even allowing for efficiency this makes the import look too high for that consumption but the actual import (as per the meter) is about 579, so way lower than what the inverter says. Saying that, I think that there was a draw today but maybe I just need to keep checking the meter as it's the only way I can know what it being drawn (it's not a smart meter).

 

Overall it looks good in that I'm averaging 5.6Kwh import from the grid from 25 Oct to now which seems like about half (if that) of what it was for the same period last year, but I want to make sure I'm not missing a trick for the summer.

 

Another aspect is that I think the battery is set up to only discharge down to 10%, though it can go to zero. The installer said that it was just set up this way to make sure it works and then it will be changed, though I suspect that this was just the default setting and they didn't change it. I've asked but it takes weeks to get a reply so if anyone has any clue how to change this then that would be great (see the second snip)! I've tried changing the 0,90 inputs but it doesn't seem to like it.

 

Thanks in advance!

 

 

 

[Pocster]

On a PowerWall ( for example ) max sustained output is 5kwh . So maybe you were drawing more than this at a particular time ? ( say oven and hob simultaneously ) .

In terms of taking from the grid when not needed it can happen fairly frequently but for short periods .

If I suddenly demand 4kwh ; I can see that I take from the grid for a few seconds to meet demand - then presumably the inverter sorts it’s life out and it takes from the battery .

 

[MrTWales]

7 minutes ago, pocster said:

On a PowerWall ( for example ) max sustained output is 5kwh . So maybe you were drawing more than this at a particular time ? ( say oven and hob simultaneously ) .

In terms of taking from the grid when not needed it can happen fairly frequently but for short periods .

If I suddenly demand 4kwh ; I can see that I take from the grid for a few seconds to meet demand - then presumably the inverter sorts it’s life out and it takes from the battery .

 

 

Thanks, I wondered about that but the draw didn't seem all that much and wasn't for that long. A later snip is below and the later draw seems OK as the battery is used then. Next time I'm going to cook in the day I'll take a photo of the meter before and after to be sure.

 

Re the max battery draw, if it's 4kwh max output and solar is generating 2kwh then can you in theory use 6kwh without needing the grid?

[Pocster]

3 minutes ago, MrTWales said:

 

Thanks, I wondered about that but the draw didn't seem all that much and wasn't for that long. A later snip is below and the later draw seems OK as the battery is used then. Next time I'm going to cook in the day I'll take a photo of the meter before and after to be sure.

 

Re the max battery draw, if it's 4kwh max output and solar is generating 2kwh then can you in theory use 6kwh without needing the grid?

I would get your installer to look at these graphs . 
But yes ; if battery is outputting 4kwh and there is 2kwh of pv - you can draw 6kwh without the grid . You do have to be careful though as pv could drop for a few seconds / minutes ( so you’ll take from the grid ) then recover .

As you say - check the meter before / after cooking - that might identify what’s going on .

[Dillsue]

4 minutes ago, MrTWales said:

Re the max battery draw, if it's 4kwh max output and solar is generating 2kwh then can you in theory use 6kwh without needing the grid?

What's the inverters rated max output?? With the PV and battery coming through the inverter, its likely the inverters output that limits the max draw??

[MrTWales]

9 minutes ago, pocster said:

I would get your installer to look at these graphs . 
But yes ; if battery is outputting 4kwh and there is 2kwh of pv - you can draw 6kwh without the grid . You do have to be careful though as pv could drop for a few seconds / minutes ( so you’ll take from the grid ) then recover .

As you say - check the meter before / after cooking - that might identify what’s going on .

 

Thanks - I will but, honestly, it takes freaking ages to get a reply. I've still not got the warranty stuff yet, though I know the forms were being completed last month, and the immersion diverter still needs to be installed (so the full amount hasn't been paid). I guess they are still flat out busy. I'm def check the meter tomorrow am and then see what happens in the day.

[MrTWales]

9 minutes ago, Dillsue said:

What's the inverters rated max output?? With the PV and battery coming through the inverter, its likely the inverters output that limits the max draw??

The inverter is fairly big I think for this system size (LXP-6K Hybrid). The box says "Max DC power = 8000w" and "Nominal AV power (@cos =1) = 6000w". Not sure what the hell all that means though if I'm honest, but maybe it means 6kw max of solar + battery? It couldn't have been that high earlier.

 

I would get a smart meter but I'm with Shell (after my green supplier went bust) so I want to change as soon as I can.

[PhilT]

It looks like there's an issue with your settings - there's three x 2+kW consumption spikes, but no battery assistance in the first two, only the third one shows 100% battery support. Post a screenshot of your charge/discharge settings so we can see what's going on.

Edited February 7, 2023 by PhilT

[MrTWales]

30 minutes ago, PhilT said:

It looks like there's an issue with your settings - there's three x 2+kW consumption spikes, but no battery assistance in the first two, only the third one shows 100% battery support. Post a screenshot of your charge/discharge settings so we can see what's going on.

 

Thanks, the only settings I can see are below. I think that there are all default. I really want to change the battery to run down 100% also as it can, but I can't work out how to do this. It looks like the "On-Grid Cut-Off SOC(%)" field maybe, as it says [0,90] but I can't change it to [0,100] as it doesn't accept it. I've asked but it's just so hard to get anything back from the installer.

 

[MrTWales]

PS I just used the pizza oven and microwave at the same time and this all seemed to come from the battery!

 

[SteamyTea]

1 hour ago, pocster said:

max sustained output is 5kwh

Ignoring your consistant misuse of units, I think you mean kW as that is power.  kWh is energy i.e. how much fuel is in the tank.

 

58 minutes ago, MrTWales said:

The box says "Max DC power = 8000w" and "Nominal AV power (@cos =1) = 6000w". Not sure what the hell all that means though if I'm honest, but maybe it means 6kw max of solar + battery?

The @cos= 1 is at 100% of possible power transfer.

AC voltage and current are out of phase by 180°.

[Pocster]

3 minutes ago, SteamyTea said:

Ignoring your consistant misuse of units, I think you mean kW as that is power.  kWh is energy i.e. how much fuel is in the tank.

 

The @cos= 1 is at 100% of possible power transfer.

AC voltage and current are out of phase by 180°.

Oh how I SO wish for a FU emoji 

[PhilT]

28 minutes ago, MrTWales said:

 

Thanks, the only settings I can see are below. I think that there are all default. I really want to change the battery to run down 100% also as it can, but I can't work out how to do this. It looks like the "On-Grid Cut-Off SOC(%)" field maybe, as it says [0,90] but I can't change it to [0,100] as it doesn't accept it. I've asked but it's just so hard to get anything back from the installer.

 

You need to click on the "Read" button first to populate all cells with the current settings, then take another screen shot we can have a look at

[MrTWales]

Thanks, I never noticed that button before. Now it looks like this.

 

Maybe the "On-Grid Cut-Off SOC(%)" needs to be set to 0 (from 10)?

 

[MrTWales]

This is the battery (actually it's three x 3.2 kwh). It can go to zero and I assume that nothing bad will happen if it does get set to zero? On the grounds that they haven't said otherwise!

 

[Thorfun]

You can set on-grid discharge to 0 but then if the power goes off you’ll have nothing left in the tank for emergency backup. 
 

the off-grid discharge set to 0 means that in a power cut you can fully drain the battery. 
 

my LuxPower inverter can discharge at a max of 3.5kW so yours is probably the same. Although mine is an AC coupled inverter rather than a hybrid. 
 

actually, looking at the spec sheet it does say 6kW AC output. But I couldn’t find what the battery discharge rate max was. 

Edited February 7, 2023 by Thorfun
Spec sheet but added

[MrTWales]

I think the inverter can do 6kwh, but I was the same with the battery in that I couldn't find out when I looked a while back. I have a feeling it may be 4kw max but I really don't know.  Actually, looking now the battery was drawing at 4.2kw this evening at one point for a short time (prob the kettle + toaster or something like that) though I'm not sure I trust all of the output from the inverter chart.

 

Re the power cut - we've had one power cut and it cut off anyway even with the battery having some juice left! I understand that it's to do with the set up and some systems can be set up to cope and others can't. It's way beyond my understanding but something I'll think about when I know the basics are working as they should. Not going to lie, I find these systems really confusing. I still can't get my head around how the inverter knows what the rest of the house is drawing when the current doesn't flow through it.

[Thorfun]

19 minutes ago, MrTWales said:

I still can't get my head around how the inverter knows what the rest of the house is drawing when the current doesn't flow through it.

CT clamps

[MrTWales]

Ah, so these things will detect the current and feed the info to the inverter via the ethernet cable? I know there is a funny looking simple thing attached to a cable in the meter box, but I thought it only detected the flow direction (so the inverter knows if there is a flow to or from the grid) but didn't realise it could actually know how much current is flowing. Damn. It almost makes sense now!

[PhilT]

Your settings are in the default "self use" state, which seems to be working ok apart from one consumption spike not supplied by the battery just after 14:00 (which could be a blip). For what it's worth, my On Grid Cutoff SOC is set to 5% and Off Grid 3%, which is what the installer set based on advice from the supplier.

 

Regarding a power cut, the installer should have put in a mains socket for you, connected to the EPS which you already have switched on (Power Backup "Enable" button in the settings, first section)

[S2D2]

37 minutes ago, MrTWales said:

Ah, so these things will detect the current and feed the info to the inverter via the ethernet cable? I know there is a funny looking simple thing attached to a cable in the meter box, but I thought it only detected the flow direction (so the inverter knows if there is a flow to or from the grid) but didn't realise it could actually know how much current is flowing. Damn. It almost makes sense now!

Yes, this CT clamp detects the import/export power to a given accuracy. The arrow is to ensure it is installed the correct way as reversing the clamp will reverse the polarity of the reading. 

 

Are you cooking with an induction hob, or just a simple resistive load like an oven? 

[MrTWales]

21 minutes ago, S2D2 said:

Yes, this CT clamp detects the import/export power to a given accuracy. The arrow is to ensure it is installed the correct way as reversing the clamp will reverse the polarity of the reading. 

 

Are you cooking with an induction hob, or just a simple resistive load like an oven? 

 

Funnily enough, the spike at 2pm was when I was cooking and part of that was using an electric hob that we just never use. We use the gas hobsusually but I thought I'd use an electric hob as I knew I'd have excess today. It's probably over a year since it's even been switched on. I think it's an induction hob in that it gets hot very quickly and seems to click off if there is nothing on it. I just did a test now and put it on for 5 mins, and the spike seems to be covered by the battery. Could the type of appliance make any difference?

[MrTWales]

1 hour ago, PhilT said:

Your settings are in the default "self use" state, which seems to be working ok apart from one consumption spike not supplied by the battery just after 14:00 (which could be a blip). For what it's worth, my On Grid Cutoff SOC is set to 5% and Off Grid 3%, which is what the installer set based on advice from the supplier.

 

Regarding a power cut, the installer should have put in a mains socket for you, connected to the EPS which you already have switched on (Power Backup "Enable" button in the settings, first section)

 

Thanks. I don't think any of this was mentioned - would this be an optional extra? The work was subcontracted but they have to come back to fit the immersion diverter at some point so I wonder if something can be done then.

 

Re the battery, the website seems to make a big deal about being able to use 100%. I wonder about using this in the summer but in the winter, when you never charge over 90% anyway, to set it back to 10% if that's better for the batteries.

[S2D2]

7 hours ago, MrTWales said:

 

Funnily enough, the spike at 2pm was when I was cooking and part of that was using an electric hob that we just never use. We use the gas hobsusually but I thought I'd use an electric hob as I knew I'd have excess today. It's probably over a year since it's even been switched on. I think it's an induction hob in that it gets hot very quickly and seems to click off if there is nothing on it. I just did a test now and put it on for 5 mins, and the spike seems to be covered by the battery. Could the type of appliance make any difference?

The induction hob switching can confuse the inverter, here's my grid usage when pulling an average of 900W to the hob but oscillating around this point as the inverter tries to keep up:

 

 

This would probably explain your messy spike just before two, but it does not explain why the inverter didn't pull from the battery at all for the spike just after two. If your installer is slow to respond you can try the inverter/battery manufacturer directly. 

[MrTWales]

Thanks, good point about trying to contact the manufacturer. 

 

Not sure if they can really do much about these issues if the basic set up is OK? It's a shame as I intended to use the electric hobs in the summer, so with the diverter to the immersion heater we'd not use any gas in any good sunny spells.

 

I've taken note of the meter reading and I'll use the hob again at lunchtime so I'll see how it goes.