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Inverter is Misbehaving


pranam

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Hi everyone

 

I'm hoping someone here can assist me with 2 annoying problems I'm having. I'm running a 2.5kwh and 3.5kwh pylontech battery on my Goodwe ES inverter (4.6kw) with firmware 5171708.

 

Problem 1:

The continuous discharge of the batteries is meant to be 62 amps with a max of around 124 amps. For some reason, I can only ever draw 50 amps from them (2.5kw). Apparently this is due to the inverter limiting the draw from the batteries to 80% of the 62 amps. However, the 62 amps is the 'stable' current so why must it restrict it even further. Is there any setting on PVmaster I can edit to force the inverter to pull 62 amps? Is there anything on the BMS I can edit? 

 

Problem 2:

This inverters just loves Eskom! When Eskom power is around it will always prefer it. It's driving me crazy now. Every night I use about 1.5kwh of power while sleeping and about 1.2kwh of that comes from Eskom :( My batteries are at over 80% when I go to sleep. I don't understand why the inverter does this. Earlier today, my system was actually pulling 2.7kw from Eskom to power the house while, at the same time, pulling 1.1kw from the solar panels and charging the batteries with 0.8kw! This is highly frustrating and has forced me to basically switch the Eskom mains off unless I need to use my iron. How do I get this thing to behave without switching my mains off? I've tried switching the work mode from "on-grid" to "back-up" but that actually made it worse! If I don't allow it to export power, it also gets worse. For example, if export power is zero then I get about 50% of my daily power from Eskom. If I let it feed back then I get about 20% from Eskom. I'm not sure what's happening with the feedback as I live in a complex so it's probably being used up by my neighbours or something 😕

 

Has anyone seen this kind of thing before? It's honestly quite a frustrating situation now as I've basically got a 4.6kw inverter that can provide only 2.5kw and then only when actively cut my power. I feel like I could have installed a 3kw inverter with no batteries and less panels and saved half my money because that's what I have right now :( 

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10 hours ago, pranam said:

Every night I use about 1.5kwh of power while sleeping and about 1.2kwh of that comes from Eskom

can you please upload the graphs from the SEMS portal of a typical night. We might be able to spot the problem. I must however mention, that a usage of 1.2kWh per night is very little. I have the same inverter and what I have noticed is that if the consumption is very low the inverter sometimes does not switch over to battery discharge mode.

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Switching from "on grid" to "backup" will make your situation worse. In backup mode the inverter tries to keep the batteries at 100% charge and draw from them only when the grid goes down. So at night you will be drawing from the grid to keep everything in your house running plus a little extra to keep the batteries charged.

It may help to describe your whole set up to us. How many panels etc, and also what sort of load you draw during the day. And, as @Fuenkli suggests, to post some portal data.

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Thanks for the replies everyone.

 

My system is as follows:

8 x 390w panels - I've included 2 pics of the generation on a fully cloudy day vs a day with no clouds

6kwh pylontech (2.5+3.5) - supposedly capable of pushing 62 amps (25+37) but the inverter is only allowing 50 amps (80% of 62😡)

Goodwe 5048ES 4.6kw

 

I generally use very little electricity. On average, when my maid isnt working, I use 4kwh a day. I've attached some pictures of it preferring Eskom and overnight. Do I need to put something on to eat up power overnight? It seems like under 100 watts it doesn't like the batteries

Loving Eskom 2.PNG

Loving Eskom.PNG

Overnight.PNG

Cloudy.PNG

No Clouds.PNG

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Picture 1 looks not surprising to me. You have a big surge about 6:30, there is some solar, but not enough to handle the load and charge the batteries, so the ES draws from batteries and grid. I am guessing that in cases such as this the draw from grid happens because there is a spike when whatever it is turns on. We don't see that spike in the graph because it is drawn from samples taken every 5 minutes and smoothed out.

 

Picture 2... hmmm.... what mode was your inverter running in? But also, the PV is consistently less than the load, so the ES has got to get power from somewhere.

Picture 3 is not as bad as it looks, because the load and the draw from the grid are low, so it switches to a different scale. What I never understand - and I see it with my own ES - is that it tends to draw from mains when the load DROPS. See a snip from my portal data.

image.png.cf8905d72135471b3619e84f62127a41.png

I do wonder if you have enough PV. In the first 3 shots the PV power available is always less than the load.

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Thanks Bobster. This is very helpful! my system has always been in on-grid mode

 

So, if I switch my Eskom mains off, picture 1 and 3 above just use the battery. If it's capable of handling the load without Eskom, and if the battery is charged, I would like it to do the same even if Eskom is there. In general, I want the system to always hit the battery first. However, it refuses.

 

Picture 2 was a rainy day. I'm not too worried about the PV on that day. I'm more worried about the battery being completely ignored. It was an iron that was running so it should have drawn something from Eskom but not everything! 2 hours of ironing from the made and the battery was asleep!

 

Any ideas on how to get the inverter to pull 62 amps?

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1 hour ago, pranam said:

It seems like under 100 watts it doesn't like the batteries

I agree. 

 

1 hour ago, pranam said:

Do I need to put something on to eat up power overnight?

I did this for a while and it worked. But because the grid consumption was so low that it was just not worth the trouble and I accepted the very small grid usage at night. You could discuss this with Goodwe. Maybe there is newer firmware with better battery management available. 

 

58 minutes ago, Bobster said:

Picture 2... hmmm.... what mode was your inverter running in?

I think it is running in "back up" mode.

 

1 hour ago, Bobster said:

What I never understand - and I see it with my own ES - is that it tends to draw from mains when the load DROPS

I think it is probably the same low load issue. The load drops below a certain threshold and the software is struggling to manage the transition. I remember @plonksterand @Coulomb explaining the reasons why it is impossible to design an inverter without any time lag in the control loops  

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51 minutes ago, pranam said:

2 hours of ironing from the made and the battery was asleep!

we discussed this before. If the on off frequency of the iron is to short the inverter will not switch to battery discharge mode. My inverter takes about 10 second before it changes from battery charge to battery discharge mode.

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1 hour ago, pranam said:

Any ideas on how to get the inverter to pull 62 amps?

you could try to disconnect the communication link between the batteries and the inverter and chose "self define" in the PV Master app battery set up. This should allow you to set all the parameters (including max discharge current) the way you want them. But be careful this will probably void the warranty of your batteries 😂

Edited by Fuenkli
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27 minutes ago, Fuenkli said:

we discussed this before. If the on off frequency of the iron is to short the inverter will not switch to battery discharge mode. My inverter takes about 10 second before it changes from battery charge to battery discharge mode.

Thank you. This explains some of my own little puzzlements, and it is of a piece with what I have observed with my own inverter. It does take a little to time to switch between charge and discharge. Usually this is not a problem in turns of continuity of normal life in the house because when the grid goes down either there is PV available, or the battery is discharging already.

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2 hours ago, pranam said:

It seems like under 100 watts it doesn't like the batteries

That might even be by design. I don't know anything about these inverters, but because the inverter needs its own power to run, it always uses more power from the battery than what your load requires, and at a certain point (somehere between 20W and 60W for most designs) the power the inverter needs to run starts to outstrip the actual power it is tasked to deliver, and your efficiency becomes less than 50%.

At this point it is usually best to just use the grid, it's almost always cheaper. Even the best batteries are not half the price of grid power... not yet anyway 🙂

It could also be simply because the inverter can't measure accurately  that low down.

Either way... I would not worry about it too much. Especially not with the goodwe's design (PV is converted directly to AC like a PV-inverter would do, and battery charging/discharging is handled via a buck-boost converter with a control loop.

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27 minutes ago, Fuenkli said:

you could try to disconnect the communication link between the batteries and the inverter and chose "self define" in the PV Master app battery set up. This should allow you to set all the parameters (including max discharge current) the way you want them. But be careful this will probably void the warranty of your batteries 😂

This is how my ES is setup. There is no communication link between batteries and inverter, and the batteries are "self defined". Because none of the pre-defined battery types suit the Revovs. 

However, because of this, you need to beware of firmware upgrades. The latest firmware will fix the wifi hassles I have, but also lacks the "self defined" battery option, so one cannot run the Revov's optimally.

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51 minutes ago, Fuenkli said:

you could try to disconnect the communication link between the batteries and the inverter and chose "self define" in the PV Master app battery set up. This should allow you to set all the parameters (including max discharge current) the way you want them. But be careful this will probably void the warranty of your batteries 😂

This is the main issue! I feel a bit cheated by Goodwe on this tbh. This 20% buffer is nowhere on any of their documentation. I would understand if they said 80% of the batteries' max output but 80% of the continuous output just seems unnecessary. 

 

I'm honestly tempted to tell the installer to send this one back and get another brand but I'm not sure which one will be better.

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18 hours ago, pranam said:

This is the main issue! I feel a bit cheated by Goodwe on this tbh

I would imagine that the max charge/discharge rates are based on an agreement between Goodwe and Pylontech. The inverter is clearly able to accept a max input of 100A from 48V (in "battery self define"). So I think the blame must go to Pylontech.

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3 hours ago, Fuenkli said:

I would imagine that the max charge/discharge rates are based on an agreement between Goodwe and Pylontech. The inverter is clearly able to accept a max input of 100A from 48V (in "battery self define"). So I think the blame must go to Pylontech.

Interesting. I have spoken to a few people who have 5kw inverters and they are running a single Pylontech 3.5kwh battery on them because it's more than capable of running the 74A max and 100A surge. That's why I think it's the way the Goodwe and Pylontech BMS communicate. Other inverters are happy to pull the required amount. The Goodwe isnt :( 

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On 2019/11/16 at 11:46 AM, pranam said:

Interesting. I have spoken to a few people who have 5kw inverters and they are running a single Pylontech 3.5kwh battery on them because it's more than capable of running the 74A max and 100A surge.

*EDIT* For a Single Battery I don't think it is a good idea for warranty purposes, as pylon themselves recommend 37A. Victron also specifically mention battery bank sizing for inverter output, because of this.

*EDIT* I see you have two batteries, so should be fine-ish.

 

Edited by PaBz0r
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