Axpert problem

[Oros]

Hi all,

I have recently installed a hybrid 10 Kva system at my home. 

Grid connected.

24 X 330W solar panels( 12 per inverter)

2 X Axpert 5KVA MKS Inverters ( Parallel connected)

2 X 4.8 Kw 48v batteries parallel connected.

When the supplier installed the system it was working, but it was clowdy/ raining.

A few days later, in the morning, on full sunlight the mppt chargers was working fine until the voltage from the panels went over 115 Volts. Then the chargers switched off and the inverter display does not show the solar panels connected. No alarm or error. The inverter just switch over to batteries. From then it works as if no solar panels is connected. When the batteries reach low level, the inverter charge them with the grid power. Later the day as the sun starts going down and the voltage from the panels goes below 115 V, the mppt chargers switch on and start charging the batteries. Like it is supposed to. Even during the day if some big clouds block the sun a bit and the voltage drop to under 115 V, the chargers switch on.

The manual states the mppt charger controllers input operating voltage is 60 to 115 Vdc. During the day the voltage goes sometimes up to 134 Vdc. I contacted the installer and they are confused why it happens as they wired the panels so that the voltage is under 125 Vdc. I don't know why they used 125 V as the limit as the max input voltage of the inverter is 115 Vdc.  With a Vmp of 36 Volts per panel, no matter how I calculate it, I do not get the voltage that I'm reading. With 3 in series with 4 parallel strings I get 108 Vmp. With 4 in series and 3 parallel strings I get 144 Vmp. 

Ok, so I decided to measure the Voc from the panels, I open the fuses and measure, but no reading. And yes, I do know how to use a multimeter. When I spoke last to the installer he wants to install a resistor in series the drop the voltage !! I told him it is not really viable to do so and not the correct way to solve the problem as it would create more problems.

Soooo, why is this happening ?????

Until next year when the installer open again, what can I check or do ?? Is the Axpert inverters faulty, is the panels wired wrong ??

 

 

[Gabriel_2018]

It is easy to solve using 2S6P config per inverter.

If pannels were 60c you could use 3s4p, but it is not this case.

[Oros]

Hi Javi,

I also think installer made a mistake wiring the panels. For warranty reasons I'm going to have to wait till they are open again to come and fix it.

I was hoping there is something in the inverter setup I could change !!

 

Regards 

[Arandoza]

Hi Dros,

if the panels are in 3S4P configuration you could try to cover the 3rd panel of each string ? Effectively shading it completely.  Until your installer could get to you? Not sure how practical this is?

Good luck, hopefully the over voltage on the mppt hasn’t caused any damage?

 

alternatively it maybe safer to

simply isolate the array from the mppt altogether, to prevent any risk of damage.

[Coulomb]

7 hours ago, Oros said:

on full sunlight the mppt chargers was working fine until the voltage from the panels went over 115 Volts.

On all the 5 kVA models I've seen with a 145 V max Solar Charge Controller, the solar charge current starts derating at 130 V. I know the manufacturer says that the MPPT range is to 115 V, but it should still attempt to pull maximum power until 130 V. From there, it should linearly derate to 145 V.

I don't know at what voltage the solar icon goes away.

Your situation sounds a little different.

Assuming that your panels are 72 cell (you can count them by inspection, be aware of 144 half-cell panels), then the only alternative is rewiring to 2S6P per inverter. These inverters really prefer 60 cell panels. They do exist, but supply may well be tight at present in South Africa.

7 hours ago, Oros said:

Soooo, why is this happening ?????

It does sound like you're getting too high a PV voltage. On older models, 134 V is still useable, it just derates the solar charge power by 4/14 = 27%. But pulling 27% power might be enough to pull the voltage to below 130 V, which would allow full power, until less than full power is needed.

It sounds like the manufacturer has changed the behaviour with high PV voltage. What is your Solar Charge Controller (U2) firmware version? For a long time, it's been 04.12 or 04.10.

Is it possible that you have a clone?

[Oros]

I will have a look at what firmware is installed. What i have seen is on the tag of the inverter it shows 

Max. Solar Voltage (VOC):  115 VDC

As soon as the voltage goes over 115 V the Watts goes  to zero and the inverter beeps, and the picture of the solar panel is gone.

No alarm code is displayed when this happens. What I don't understand is that the manual states the VOC  as 145 VDC, but not the tag.

 

 

[Coulomb]

On 2019/12/31 at 1:29 PM, Oros said:

Max. Solar Voltage (VOC):  115 VDC

Wow. It does indeed. That's the first time I've seen that. This seems to be a new "feature" 

Quote

No alarm code is displayed when this happens. What I don't understand is that the manual states the VOC  as 145 VDC, but not the tag.

Oh, the paper manuals are often well behind the web specifications, and the web specifications (which still say 145 V max) seem to be behind the actual hardware now.

And your model was manufactured in July 2019, so it's not like they've just made the change last week.

I wonder if they've decided that there are too many problems with 72-cell panels wired as 3S, so why not force everyone to use 2S.

EDIT: Alternatively, perhaps this is a PWM model, and they have increased the maximum PV voltage to 115 V. I hate how they don't mention whether it's a PWM or MPPT model on the sticker.

EDIT August 2020: I now believe that this is a typo on the sticker. Later models have "Max Solar Voltage (Vmp) : 115 VDC". I think they just wanted the 145 V figure off the label, because it's over 120 V, the upper limit for Extra Low Voltage.

Edited August 10, 2020 by Coulomb

[Oros]

U1 -----   72.3

U2 -----  01.1

How would I find out if it's a PWM or MPPT model ?

[Coulomb]

8 hours ago, Oros said:

U1 -----   72.3

U2 -----  01.1

How would I find out if it's a PWM or MPPT model ?

The 01.10 looks unusual.

When charging the battery and it's not close to full, is the PV voltage the same as the battery voltage?

You mentioned 115 V when the panels disconnected, but was it around 53 V when the battery could take all the charge current from the panels?

Even better: do you ever see a higher battery charge current than panel current? Only an MPPT charger can do the "DC transformer" thing. With PWM, the current will be the same or less into the battery than from the panels. Check when AC loads are low.

Finally, the PWM hardware is smaller than the MPPT hardware; the latter is a PCB that is basically the full height of the inverter. This is obvious with the lid off, but you might be able to tell with a torch through the fan holes without taking off the lid.

[Oros]

All the info I have I get from the software supplied with the inverter. So I can only see the PV voltage and wattage. Not the amps from the panels.

The charge amps I see is dependent on the wattage from the panels. It does not matter if the batteries are full or empty, load big or small, as soon as the voltage goes over 115 V  the panels disconnect and under 60 VDC no watts. What worries me is that I have searched and searched on all sites on the internet, and I have not found ANY axpert inverter with VOC of 115 VDC. I must admit, mine is VOLTEX inverters, but looking at the manuals they are actually the same. I just don't understand that I could not find any other with the same VOC. I have send the maufacturer an mail to see if they can shed some light on the issue. 

The system works perfectly as long as the voltage is under 115 V. I nearly went 2 days running only on the system, before it switch to grid to charge the batteries. I do not know how the installer wired the panels, but I do think he was under the impression that the VOC is 145 VDC, as ALL Axpert MKS 5KVA is configured to, because when I queried the problem he stated that it was wired so that the VOC is +- 125 VDC.

So I will contact them again as soon as the open in the new year to come and investigate, as the system is under warranty by them and it is a brand new installation  (November) and I paid a fortune for it.

I will let you know what was the solution (problem) as soon as it is fixed.

 

[Gerrie]

29 minutes ago, Oros said:

So I will contact them again as soon as the open in the new year to come and investigate, as the system is under warranty by them and it is a brand new installation  (November) and I paid a fortune for it.

This is not right, if these guys are in this kind of service industry do they not have a standby guy over the festive season?

 In the mean time you loose money day-by-day for a white elephant that’s not producing any power. This to me is bad service surely they should have handed over this installation with the necessary testing and documentation. I hope you get this solved. 

 

 

[Oros]

1 hour ago, Gerrie said:

This is not right, if these guys are in this kind of service industry do they not have a standby guy over the festive season?

 In the mean time you loose money day-by-day for a white elephant that’s not producing any power. This to me is bad service surely they should have handed over this installation with the necessary testing and documentation. I hope you get this solved. 

 

 

Yep, I agree. But unfortunately for me is that they are in Nigel and I am in Polokwane. 360 km away. It is not a quick go and check/fix.

Soooooooo, I must maar wait and see when they will be willing to take the trip. Before I make a big scene I want to give them the opportunety to fix it.

[Oros]

On 2020/01/01 at 3:26 AM, Coulomb said:

The 01.10 looks unusual.

When charging the battery and it's not close to full, is the PV voltage the same as the battery voltage?

You mentioned 115 V when the panels disconnected, but was it around 53 V when the battery could take all the charge current from the panels?

Even better: do you ever see a higher battery charge current than panel current? Only an MPPT charger can do the "DC transformer" thing. With PWM, the current will be the same or less into the battery than from the panels. Check when AC loads are low.

Finally, the PWM hardware is smaller than the MPPT hardware; the latter is a PCB that is basically the full height of the inverter. This is obvious with the lid off, but you might be able to tell with a torch through the fan holes without taking off the lid.

Some days with the light just correct with the voltage under 115 V I get about 3200 Wats per inverter and the total charge current is 80 Amps. On average I consume about 2500 watts during the day but can go up to 5000 watts for short periods. Depends if I run my borehole pump watering the garden, ironing of clothes and pool pump running.

[Oros]

Ok guys, now I need serious info. The installer informed me that, yes the voltage is too high. He managed to find a resistor that he is going to install next week to drop the voltage. I do not agree with this solution. NOWHERE have I seen any resistor that solar suppliers supply to drop the voltage. Yes, if you find one, it will drop the high voltage, but because it is a fixed resistance resistor, it will affect the startup voltage of the charge controller. So on a day that the sun is not good, the system will sometimes not work, as the the resistor drops the startup voltage !!!

Have anyone heard of such resistor (solution), and if you have, do you have any info regarding this solution. All I can find on the web is that the panel configuration would need to change. From 3S4P to 2S6P. The panels is 330W 72 cell.

 

[JacquesVDM]

A resistor is not the solution. Changing the configuration is the correct way. 

By using a resistor to drop the voltage, some power will also be lost. (Power loss will be heat generated in the resistor.) 

It is like having to much water pressure in a pipe and adding an extra tap to "drop" the pressure by letting it flow to the drain. 

I have never heard of anyone adding a resistor. Sounds like the installer is looking for a quick fix. 

 

[Coulomb]

2 hours ago, JacquesVDM said:

A resistor is not the solution.

If it's just a series resistor, it won't even work most of the time. As soon as a cloud goes by and the current goes down, the voltage drop across the resistor will go down, and the voltage seen by the inverter will go up. So then it disconnects, then the current is zero, and it won't connect again until there is almost no sun. At least, that's how I see it "working".

Quote

Changing the configuration is the correct way.

Absolutely. Unfortunately, it's a lot of work. Another way is to replace the 72-cell panels with 60-cell panels. Even more work, and you'll probably lose power.

I'm starting to think that this inverter is a freak. Possibly a clone, but I've never seen such a genuine-looking label on a clone. Can't be that hard, though (edit: to accurately copy the style of a label). So an easier solution might be to replace your inverter with an actual 145 V max model. Then use your inverter on some other site wired 2S.

You may still have over-voltage issues now and then, but nowhere near as bad as this.

Edited January 3, 2020 by Coulomb

[Chris Louw]

@ Oros if you do get to know why the max solar volts is 115 VDC please share with us . Thanks .

[Oros]

Hi Guys,

Ok, so the inverters was supplied by Voltex and is not dud's. The VOC of their 5KW is 115 VDC. I indicated to them that what they are advertising and selling

is not the same. They did not notice it. Looks like the latest batch (date same as mine) they received the VOC and max operating voltage is the same, 115 VDC.

I think the guy that installed my inverters did not notice that the spec's of the inverters changed, hence the wrong configuration wired. Now it is a waiting game too see when they are willing to come and fix it. On Monday I spoke to the owner of the company and he promised that in this week they will come, but ja, still waiting and no communication from them.

Now I just hope the new configuration, 2s6p, will work. I think the system will only start working a bit later in the morning and stop a bit earlier the afternoon. On cloudy days is anyone's guess as to how well it is going to work. 

[Chris Louw]

@ Oros good information . We are all used to the 145 volt spec . Thanks

[Shockin]

Voltex doesn't seem to realise that they are false advertising and steps can be taken against them for it.

[Shockin]

Oops please excuse my previous post,  my bad

Edited January 10, 2020 by Shockin

[Gerrie]

14 hours ago, Oros said:

Now I just hope the new configuration, 2s6p, will work.

I’m sure this will solve your problem. Mine is 2xseries and work fine. But I do have a clone inverter that is max solar voltage(voc) = 105vdc

[Oros]

Hi Guys

So eventually the installer change the wiring of my panels. 2S6P per inverter. Works nice, but now an new issue!!

As soon as the voltage goes above 80 VDC the MPPT charger switches off!! The working voltage of the inverter is 60 to 115 VDC . So now that the voltage is lower, the same problem but at a lower voltage !! 

Does anybody know why that is happening. The max VDC so far from the panels is 88 VDC with the new configuration.

 

[Coulomb]

16 hours ago, Oros said:

As soon as the voltage goes above 80 VDC the MPPT charger switches off!!

That's weird. Does it come back if the panels go below 80 V, say near the end of the day?

I assume it can't be because the battery is full by then, and you have no significant loads.

Is setting 31 (solar balance) on?

If you isolate your panels and re-connect them, does it start again? You might be running into the dips and freezes issue.

[Oros]

On 2020/01/24 at 1:44 AM, Coulomb said:

That's weird. Does it come back if the panels go below 80 V, say near the end of the day?

I assume it can't be because the battery is full by then, and you have no significant loads.

Is setting 31 (solar balance) on?

If you isolate your panels and re-connect them, does it start again? You might be running into the dips and freezes issue.

I think it happens when the batteries is full and not a big load from my house. Been monitoring it now for a while and looks to be ok. I am waiting for my ICC unit to connect to the inverters as the software that came with the inverters is not so informative, and i have to select between the 2 inverters too see what they individually supply. I'll have a look at setting 31.

A weird thing happend now today, for the first time, as soon as i switch the lawnmower on i get a error code #80 on the one inverter and the output switch off. First time this happened.

I bypassed the inverters to cut the grass!!