Installed an Axpert VM111 5kw running from x 10 220 watt panels rigged in two strings and charging x2 3.5 kwh pylontech batteries. Ran beautifully for 8 months but recently the inverters inbuilt Controller Charger has stopped working...the problem originally was intermittent and I found by switching batteries and array off and on would eventually allow the charger to start it's job although at what seemed much less amps than array gives (amps measure 14.2 on amp meter but inverter screen said between 5 and 7) Now it's not working at all.....screen reads volts (142 volts) but simply doesn't kick in. I've checked feed from array and at point of entry into inverter is reading 14.2 amps. 

Any clues or is it toast ?

best

Andy

If it ran fine for months and nothing changed then it sounds like the inverter has given up. Can you post a pic of the side of the inverter with the specs on it? If it is a low voltage model then 142V is very high if that is the real voltage of the panels. What is the stated Voc of the panels?

On 2022/09/08 at 10:12 PM, AndyEliot said:

Now it's not working at all.....screen reads volts (142 volts) but simply doesn't kick in.

The specifications say that the start-up voltage is 150 ± 10 VDC. So 142 V is right at the bottom end; it could need as much as 160 V to get started.

One possibility is that 8 months after installation, you are getting some shading that you didn't get at installation. Are you in the northern hemisphere? If so, you will be starting autumn, and 8 months ago it would have been summer. The shading might be reducing the string voltage.

Would it be possible to add another panel to each string? They should nearly match the other panels, which might be hard to find these days. At least, the two string nominal voltages should agree within 5%, otherwise one string could drive current into the other string.

On 2022/09/08 at 10:12 PM, AndyEliot said:

amps measure 14.2 on amp meter but inverter screen said between 5 and 7

DC clamp meters often have pretty bad offsets (not reading zero with no current) and drift. But that's a pretty bad discrepancy. I assume that was on the screen showing the "INPUT" segment to the left of the "PV" segment. There is another data screen with "BATT" to the left of "PV"; that's charging current on the battery side of the solar charge controller. That one is probably net current after sending some current to the load via the DC-AC converter.

21 hours ago, jumper said:

If it is a low voltage model then 142V is very high

The VM III (Roman three, not decimal one hundred and ten) is a 500 V max PV model.

The sticker will also tell us whether it's a clone or not. Some clones use poor quality components, and capacitors may dry out etc., causing problems.

Is it possible that you've had a lot of rain lately? Rain can cause leakage of some panels to earth, which can cause problems such as pushing up the DC bus voltage. If the DC bus voltage is too high, the inverter will stop using solar power, though eventually it would stop with a fault code F08.

17 minutes ago, Coulomb said:

The specifications say that the start-up voltage is 150 ± 10 VDC. So 142 V is right at the bottom end; it could need as much as 160 V to get started.

One possibility is that 8 months after installation, you are getting some shading that you didn't get at installation. Are you in the northern hemisphere? If so, you will be starting autumn, and 8 months ago it would have been summer. The shading might be reducing the string voltage.

Would it be possible to add another panel to each string? They should nearly match the other panels, which might be hard to find these days. At least, the two string nominal voltages should agree within 5%, otherwise one string could drive current into the other string.

DC clamp meters often have pretty bad offsets (not reading zero with no current) and drift. But that's a pretty bad discrepancy. I assume that was on the screen showing the "INPUT" segment to the left of the "PV" segment. There is another data screen with "BATT" to the left of "PV"; that's charging current on the battery side of the solar charge controller. That one is probably net current after sending some current to the load via the DC-AC converter.

The VM III (Roman three, not decimal one hundred and ten) is a 500 V max PV model.

The sticker will also tell us whether it's a clone or not. Some clones use poor quality components, and capacitors may dry out etc., causing problems.

Is it possible that you've had a lot of rain lately? Rain can cause leakage of some panels to earth, which can cause problems such as pushing up the DC bus voltage. If the DC bus voltage is too high, the inverter will stop using solar power, though eventually it would stop with a fault code F08.

Hey Coulomb thanks for the response

So ...I'm located in Souther Spain so plenty of sunshine at present... Definitely no shading.. Could I join all ten panels in 1 string and see if that helps re: start up?

Yes the reading is from PV segment and looking at the Batt screen that's reading below PV amp input

The sticker on side says MPPT operates between 120V-450V (see pic)

Unfortunately we're suffering a major drought here so no rain lately The system was working well through winter into spring

22 hours ago, jumper said:

If it ran fine for months and nothing changed then it sounds like the inverter has given up. Can you post a pic of the side of the inverter with the specs on it? If it is a low voltage model then 142V is very high if that is the real voltage of the panels. What is the stated Voc of the panels?

Hey Jumper I've posted a pic below....

 

1 hour ago, AndyEliot said:

Could I join all ten panels in 1 string and see if that helps re: start up?

1 hour ago, Coulomb said:

The specifications say that the start-up voltage is 150 ± 10 VDC. So 142 V is right at the bottom end; it could need as much as 160 V to get started.

I think this might be the best idea, I think @Coulomb is correct (obviously 😉) regarding the low voltage of the panels. As you say it worked fine in Winter and Spring, it could be the increase in temperature as the panel voltage decreases with increasing temperatures. Putting them in a single string should give you around 280V which puts you much closer to the nominal operating voltage of the SCC and well under the limit and above 160V.

Thanks Jumper

Still doesn't explain the low amps though. i've x 10 panels at present in two strings here's their spec (see photo)  Max amps showing on the inverter is around 6 but constantly shifting and watts waiver around 400w (max 700 but very rarely)

Strangely the system started charging on it's own accord today at around 1100am and produced around 2.65kw in full Spanish sun all day (1100-1800) Ambient temp of around 30 in shade I reckon I should be getting more than that. What do you think?

 

Just now, AndyEliot said:

Thanks Jumper

Still doesn't explain the low amps though. i've x 10 panels at present in two strings here's their spec (see photo)  Max amps showing on the inverter is around 6 but constantly shifting and watts waiver around 400w (max 700 but very rarely)

Strangely the system started charging on it's own accord today at around 1100am and produced around 2.65kw in full Spanish sun all day (1100-1800) Ambient temp of around 30 in shade I reckon I should be getting more than that. What do you think?

 

 

35 minutes ago, AndyEliot said:

Max amps showing on the inverter is around 6

Looking at the panel spec it is almost as if 1 string isn't being seen by the inverter or something is damaged somehow as it is showing half as much current. Your amp meter readings seem to be more correct for the panels. Could there possibly be a loose connection where the 2 parallel strings are joined or some other wiring issue between where you are using the amp meter and the inverter itself? If 1 string is problematic there will be no change to the voltage seen by the inverter (142V matches the specs), but the current would be halved. I would expect to see at least 2KW from the panels at 12 o'clock if their angle is good, but the PV produced will only match your loads once the battery is charged.

I thought similar and measured amps beyond where the two strings are joined and got a 14 amp reading  (this is at fuse box just before inverter/charger)

So sort of think the wiring from the array is good.  Could it be the fuses? I'll check tomorrow Thamks for your suggestions it sure is helping narrow things down

 

It looks like those panels are 60 cell. So 5S is definitely not enough.

If you are measuring 14A after the strings are paralleled, then that's fine. The 5-7A at the inverter is strange, but it might just be the strange way that Axperts report PV current.

In summer, especially at 30°C, power can be less than you might expect. Say 70% of nominal, lor about 1.5kW. Certainly rewire them as 10S and see how it goes. Boosting from around 140V to a vus voltage of some 350V (more than 2:1) might be causing your solar charger to overheat and reduce power as a result. 

Just a few comments.

1. If 14A was measured it means the actual current was flowing through the circuit and has to go somewhere so this indicates the circuit is complete. A blown fuse on 1 string would have reduced the 14A to 7A. Can the current that gets to the batteries during the 12h to 14h time not be measured when batteries are discharged and no load on the inverter instead of relying on the inverter measurement?

2. No matter which funny way the Axpert reports current it can only be the same or more than what is flowing from the panels. 142V side or 48V side.

3. If there is a high load connected to allow the inverter to produce high PV to load/battery then values are too low for the conditions.

4. I take it the 2.65kw production in good sun yesterday is 2.65kwh as 10 x 220W panels at 30 deg ambient temp would normally not provide a peak as high as 2.65kw but closer to 1.8-2kw during peak hours.

5. If one used a rough guide my 60 cell panels in full sun at 28 deg in spring shows a Vmp=27V. I do feel it is save during a normal summer day to connect all 10 in series just to see if the PV does improve. My panels would then give a 135V vs 142V and it is close to the lower end of the MPPT operating range.

6. Even on cold days the 10 panels in series Voc will be around 400V which leaves a good margin of safety to 500V maximum allowed.

7 hours ago, AndyEliot said:

So sort of think the wiring from the array is good.  Could it be the fuses?

Yeah, from your amp meter reading the array wiring looks fine (as in no faults). The fuses should be fine, as @Scorp007says the circuit is complete as the current is flowing and the amp meter reading is correct for the setup.

6 hours ago, Coulomb said:

Boosting from around 140V to a bus voltage of some 350V (more than 2:1) might be causing your solar charger to overheat and reduce power as a result. 

I don't know a whole lot about the inner workings, but could this conversion cause the current to appear to halve if the inverter reads it after the boost? This could explain the difference between amp meter and inverter readings.

6 hours ago, Coulomb said:

Certainly rewire them as 10S and see how it goes.

3 hours ago, Scorp007 said:

I do feel it is save during a normal summer day to connect all 10 in series just to see if the PV does improve.

These guys know a lot more than I do, I think this is the best way forward and see where you go from there.

1 hour ago, jumper said:

I don't know a whole lot about the inner workings, but could this conversion cause the current to appear to halve if the inverter reads it after the boost? This could explain the difference between amp meter and inverter readings.

I suppose it's possible, but I've never heard of that happening.

Problem solved....I joined the 2 strings together and now have just one and the increase in voltage has totally sorted the problem So Coulomb you were spot on The Advent VMIII needs more than the 120 volts indicated on spec to run properly. Thanks for all your help.

4 hours ago, AndyEliot said:

Problem solved....I joined the 2 strings together and now have just one and the increase in voltage has totally sorted the problem So Coulomb you were spot on The Advent VMIII needs more than the 120 volts indicated on spec to run properly. Thanks for all your help.

Glad you got it going as it should. Still a mystery where the 14A went if the MPPT did not convert it to usable power. Lesson here is as Coulomb said. Always get the voltage a tad higher than the minimum spec level. Tolerances at play due to mass production.

Edited September 15, 20223 yr by Scorp007