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Lights Flickering when on Battery Mode Axpert


Rick C
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Hi all,

 I´m a newbie in solar, and so far, I'm very happy with that, but the only one problem that I have is an annoying flickering in the lights (leds , but the incandescent bulbs also) when the system is working on battery mode and an inductive load starts. Especially, the washing machine (300W, and probably 3000W surge) and its permanent start-stop. Hair dryer also affects badly. That doesn´t happen on Line Mode.

I have the Axpert plus tri 5KW, firmware 76.1 250 AH in 48V, and 3000 W on panels.

1. Could that change in current/voltage/frecuency affect the rest of appliances of the house, like the computers, leds or another sensitive devices?

2. Does anyone have the same flickering problem with those inverters? I replaced the inverter for a new one and the problem persists.  

Additional information.

    - The batteries are connected to the inverter using 21 mm2 gauge Wire, and the connections are tight enough. The flickering occurs no matter if there´s plenty solar power or is draining a lot of power from batteries.

    -  The distance from inverter to AC switchbox is near 20 m, and the wire is 4 mm2 gauge.

Possible answers,

      - The 4 mm2 for 20m could affect the capacity of the inverter in react to these sudden loads. (can serve that load, but not fast enough). The solution is replace them for thicker wires (10 mm2)

      - Worst case scenario: Axpert can't manage inductive loads very well, and  I have to buy another small inverter for the lights and pray for the instabilities in current won´t affect the appliances connected to the load.

 

I would appreciate any help/experience.

Thanks in advice 

 

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Thanks Chris,

I suspected (and prayed for) that the problem was that. Does anybody have an installation with so long cabling from inverter to AC switch box?  I think in almost all cases, they're very close. But, I never read anything about AC wiring. Everybody was worry about DC wiring and losses.

Rick C

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One other question, Rick C: Is your neutral still connected to your appliance earthing system when you are not running on mains, i.e. running the inverter? Without your neutral being earthed properly at the supply (in this case the inverter), the system is prone to all sorts of interference.

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4 hours ago, Rick C said:

2. Does anyone have the same flickering problem with those inverters? I replaced the inverter for a new one and the problem persists.  

It depends on the size of the load. I have a relatively small 1600VA inverter that drives essential loads and lights. When the fridge and freezer start there is hardly any flicker (90W, around 450W peak). When the 350W pressure pump starts there is a clear dip in the light level, and when the 900W well-point pump starts it feels like the power goes down for half a second!

I suspect it depends very much on the design of the inverter. This one has a boost converter that multiplies the input voltage by 8, and then bucks it again from there. This buck converter will be a switch mode power supply, which means it has a closed control loop that regulates the output voltage. And then it will usually have a couple of large capacitors on the bus to smooth things out and store some energy, and from there it will then chop the DC up to create AC.

A large load starting will always drop the voltage on those capacitors until the SMPS reacts. So the extent of the dip depends on the size of the caps and the speed of that SMPS. In other words... I don't think anything is wrong with the inverter. I also don't think it has to do with the power factor of the load, except perhaps to the extent that the KVAR is probably significant (in other words, the current demand is high on startup).

Induction motors usually have a startup peak of around 5 times nominal. So a 300W motor will have a 1.5kw start peak.

In other words, you may have to live with this. Or get a different inverter for the lights. Just remember that the starting peak also drops the battery voltage a bit, so some of the effect might still filter through, even with a separate inverter.

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 Solarwind,

   As I can see, every wire is properly connected , I mean, the blue and the green-yellow one (Neutral and Earth) as indicated in the manual. The inverter is conected to the grid in the same way. How a neutral could be earthed not properly at the supply? Excuse me, I'm not an electrician, just a humble solar user.

 

Plonkster,

  I was thinking to install an additional little inverter just for the lights and some help charging using the grid when voltage drops under 50V, avoiding excessive draining from batteries (40 A or more) I think is a good idea for combine solar and grid at the same time.

But actually, my concern is to avoid damage in some sensitive appliances (boiler, computers , etc) with those fluctuations in the current.

 

Thanks  

      

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Hi Rick does your inverter have a setting 38 (Allow neutral and grounding of AC is connected together . When enable inverter can deliver a signal to trigger grounding box to shot neutral to grounding ) Mine is set to Disable no flickering .

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Why would neutral bonding have an effect on flickering? The earth wire is for fault currents only and in a working system has nothing on it. Forgetting to bond it will be unsafe, but should not cause flickering. Maybe some noise generated in one appliance might be communicated to another, but I would not expect that to show up in light levels (the frequencies would be too high for the human eye).

Also, never add a second earth/neutral bond while the grid is connected. You already have such a bond either at the transformer up the street (TN-S), or where it enters the premises (TN-C-S), or sometimes at numerous points in the street (PME). You should not have working current on an earth wire and adding a second bond causes that rule to be broken.

You should however bond earth and neutral while in inverter mode, and that is what the grounding box is about on the Axpert. On the Multiplus it's built in.

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Thanks Plonkster for the explenation  I am also no electrician . Rick a few years ago I tried to use setting no 4 power saving mode SEN . that caused the lights to flick if it was the only  load on . As soon as a high load item was switched on everything was back to normal lights and all . It seems if the inverter does not power up on very small loads (4 watts ) on SEN . Setting it back to SdS solved my problem

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2 hours ago, Chris Louw said:

power saving mode

Yup. But I fear we're being ambiguous now about what is meant by flicker.

There is the kind you get with the power saving modes of inverters, where the inverter literally energises the line in short blips and if it finds something to sink the current into it will turn on. With this kind, you generally see any small lamps and appliances that are plugged in turn on and off a few seconds apart, lights litterally strobe once every second or so.

Then there is the other kind of flicker... the light is on and working properly, but it seems to flutter just that little... like a small misfiring petrol-driven generator. When larger loads turn on it visibly dips, computers might reboot, audio equipment might turn off and back on... the kind of thing that happens in very small towns when a visitor plugs in a hairdryer.

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Plonkster,

 You have describe the problem perfectly, good example about the hairdryer. Also, parameter 4 is SDS

I can´t believe that a 5KW inverter could not properly manage 300W inductive loads. As additional information, when the pool pump starts (3/4 hp), it´s just one flicker, after that there´s not problem at all. But the most annoying problem is the flickering when the washing machine is running, because it starts/stops/reverse running all the time.   

   Thanks all for your opinions. But so far, I still have doubts. 

1.) The thin 4mm2 gauge  20m lenght wire in the AC to mains could be guilty or not?

2.) If the inverter is connected as seen in the manual, what could be the confusion about neutral/earth? The neutral wire and earth wire are both connected to the same kind of wires in the switch box (mains).

 

 

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9 minutes ago, Rick C said:

1.) The thin 4mm2 gauge  20m lenght wire in the AC to mains could be guilty or not?

4mm^2 square should be good? Or am I missing something?

Just put an old analog volt meter on it (if you can find one), or maybe a DMM (though the effect is less noticable depending on the update rate of the meter). If you see the needle dip with each spin of the machine, then you know it's just the inverter not capable of regulating the voltage that well. And that is not necessarily a bad thing, some inverters do better, some do worse.

One particular LED lamp in my house always have a slight flicker when on the inverter despite it being a 5W lamp...

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Plonkster,

 That´s the point. The installation was made with 4mm2 wires from inverter to mains, I think they should be thicker, but I'm not sure if that affects how fast the voltage regulation from the inverter occurs. The ticker the wire (or the closer the inverter to mains) the faster the regulation? ==> final solution?

But so far, nobody has written about the flickering, but I think I'm not the one with flickering issues. (Remember, I had to  change  the inverter, but for other reason: The problem persists).

I´m going to use a voltimeter. And again... Could those voltage variations affect sensitive devices???

 

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22 minutes ago, Rick C said:

from inverter to mains

The flickering happens when in inverter mode. In Line mode it is fine, if I understand you correctly. Then the problem cannot be on the inverter-to-mains wiring as that wire carries no current while inverting, right?

23 minutes ago, Rick C said:

Could those voltage variations affect sensitive devices???

I doubt it. Depends on the voltage. A 5% move up and down, or around 10V, is not going to cause anything any trouble.

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23 hours ago, Rick C said:

That doesn´t happen on Line Mode.

The same 4mm2 wiring carries the current in line mode and battery mode so the problem is not with the wiring (even though I would have used 6mm2 at least), it must be slow regulation by the inverter.

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Here is my 2 cents. Son's computer was on a 10m lead. If anything switches at the inverter, his computers switches off.

So I put his PC on a cheap UPS, problem solved.

The extension lead had thin wires, not lekker thick like some you do get. 

@Rick C - a thought, as I followed a very similar path as you, as I ended up getting a dedicated small inverter for lights only, it ran off the main systems batteries.

In the end I realized, lights on batteries (obviously people switch them off, they are good LED's) ... Eskom is cheaper, the way my system works.

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40 minutes ago, pilotfish said:

The same 4mm2 wiring carries the current in line mode and battery mode so the problem is not with the wiring (even though I would have used 6mm2 at least), it must be slow regulation by the inverter.

Yep, but the thing is how it affects the speed of the inverter to react to the sudden loads, not the ampacity of the wire itself. Obviously the speed of the grid is huuuuge and always available. But in the inverter is limited.  4 mm2 wires could affect how fast it reacts? 10 mm2 could improve the situation?

20 minutes ago, The Terrible Triplett said:

a thought, as I followed a very similar path as you, as I ended up getting a dedicated small inverter for lights only, it ran off the main systems batteries.

In the end I realized, lights on batteries (obviously people switch them off, they are good LED's) ... Eskom is cheaper, the way my system works

Thanks @The Terrible Triplet , A second little Inverter is a good solution, not cheap at all, but a solution. 

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3 minutes ago, Rick C said:

A second little Inverter is a good solution, not cheap at all, but a solution. 

Little tip. Make sure it is pure sine wave, or you may get more issues.

Victron's small little inverters (180-800w) are very well priced is what I would do.

Connect invertjie to your battery bank and forget about it.

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Hi Rick

It is something peculiar to your install. Either your washing machine has some weird harmonics, or there could be a voltage drop under high load in the 4mm2 which is effecting lights (I presume they are LEDs). Having swapped the inverter out and not having remedied the situation I think you can rule out it is your inverter. It is the response to inverter current rather than the inverter itself. 

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Is the flickering on all of the lights? Have you tried putting one incandescent globe in amongst the LEDs? Sometimes it's the globes themselves.  Do you have any electronic dimmers on the light circuts, they might cause the problem. Do you have any underground cables that could be damaged and arcing to earth? Are the live and neutral connections the right way round? That's where I would start.

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1 hour ago, Chris Hobson said:

voltage drop under high load in the 4mm2

One way to test that is to put a light at the inverter (or upstream of the cable) and see if the washing machine causes the same effect. If the light still flickers, it is not the cable.

Edited by plonkster
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1 hour ago, seant said:

s the flickering on all of the lights?

All the lights, and lamps connected to the plugs. In the incandescent bulbs the flickering is really noticeable( I only have four, the rest are leds or tubes). Lights are in an independent circuit in the switch box, not in the washing machine one .

 

1 hour ago, seant said:

Do you have any electronic dimmers on the light circuts

Nop

1 hour ago, seant said:

Do you have any underground cables that could be damaged and arcing to earth?

In that case, safety switches would enter in action.

2 hours ago, Chris Hobson said:

(I presume they are LEDs

Both them

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9 hours ago, Rick C said:

In that case, safety switches would enter in action. 

No not always, I had a fault with a cable that fed a swimming pool pump not on the earth leakage onmain board in the house , that caused flickering of lights and the TV to go into stand by. If not all of the lights in the house are flickering , try plugging your washing machine into a different plug circut and see if the lights still flicker

Edited by seant
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