Axpert MKS II 5kW Error 08

[Coulomb]

4 hours ago, charlez said:

• Bypass mode
• Moisture on panels
• Been in bypass mode for quite a while, multiple hours

Ah. I run in battery mode 98% of the time, so I tend to assume everyone else does too.

Bypass / line mode (the same thing except for King models) seems to be the most delicate balance between towards utility and towards bus power flow, at least when the inverter is running. Being in bypass mode for quite a while allows integral windup to build up. Then if the mains voltage suddenly rises, the control algorithm isn't agile enough to prevent a surge of power into the DC bus, which must be what's triggering fault code 08 (error 08).

So I'm now back to my earlier theory (which I have to admit I'd forgotten about), which is that they have the inverter turned on when there doesn't seem to be a need for it. I'm still missing a few pieces of the puzzle though.

[charlez]

@Coulomb I think you are on to it. When mains voltage has peaked at 240v or so has been a feature of the problem. This is what I sent to my supplier when it first happend.

Inverter went down at point 1 on graph, restarted a few times between 1 and 2 but same issue with error "08" caused inverter to fail. So left off from 2 to point 3.

Hope this helps.

Charles

 

 

[APV]

1 minute ago, charlez said:

@Coulomb I think you are on to it. When mains voltage has peaked at 240v or so has been a feature of the problem. This is what I sent to my supplier when it first happend.

Inverter went down at point 1 on graph, restarted a few times between 1 and 2 but same issue with error "08" caused inverter to fail. So left off from 2 to point 3.

Hope this helps.

Charles

 

 

@Coulomb The bus voltage does not go to 500V in a matter of milliseconds - it takes a couple of minutes in most cases.  I cannot believe that the software is not agile enough to handle it, should a mains voltage rise be a contributing factor.  Maybe there is some kind of runaway condition triggered by a mains spike, but then why does it happen only when the panels are wet (in the majority of the cases) ???

[charlez]

8 minutes ago, APV said:

@Coulomb The bus voltage does not go to 500V in a matter of milliseconds - it takes a couple of minutes in most cases.  I cannot believe that the software is not agile enough to handle it, should a mains voltage rise be a contributing factor.  Maybe there is some kind of runaway condition triggered by a mains spike, but then why does it happen only when the panels are wet (in the majority of the cases) ???

This thread gives Voltronic a lot to go on.

Edited May 29, 2020 by charlez

[Coulomb]

1 hour ago, APV said:

The bus voltage does not go to 500V in a matter of milliseconds - it takes a couple of minutes in most cases.  I cannot believe that the software is not agile enough to handle it

Good point, but perhaps the hours spent in bypass mode allows unlimited integral wind-up. Even watching battery voltage on my system with 10 second updates it's frustrating... "the voltage is high, back off. Ok, back off the current. BACK OFF NOW, DOOFUS! CLUNK! Too late, the BMS dropped out the PV contactors again. I'm pretty sure that this overshoot is due to integral wind-up.

I can imagine a small power flow error that is too small for the system to correct. But over time, perhaps minutes, that small error can integrate (accumulate) to a large value that in some circumstances, like a slow upwards drift of utility voltage, might be countered by the huge integral factor. There are simple algorithms to avoid most of the effects of integral wind-up, but they don't seem to use them.

But as I type this, I realise that this is usually only a problem when the control system is at a limit, like maximum power from the panels. At medium power, it would not be near any limit. Oh wait, in bypass mode, there is a limit, zero current. And a little PV power, especially when unexpected perhaps, would require slightly negative charge power, i.e. exporting that small PV power. I'll bet that there is code to prevent that, hence the limit, hence the integral wind-up.

Normally, the DSP would control high bus voltage by reducing PV power. But the leakage power from rain can't be turned off.

I think I have some more pieces to this puzzle now. 

Edited May 29, 2020 by Coulomb

[StrikerX]

1 hour ago, APV said:

@Coulomb The bus voltage does not go to 500V in a matter of milliseconds - it takes a couple of minutes in most cases.  I cannot believe that the software is not agile enough to handle it, should a mains voltage rise be a contributing factor.  Maybe there is some kind of runaway condition triggered by a mains spike, but then why does it happen only when the panels are wet (in the majority of the cases) ???

In my case, it takes 1-3 sec for it to ramp up and voila! error 08. Had a shutdown around ~9:30AM on 26th.

This might be useful.

QPIGS raw log(timestamped) leading upto the error and 5min later when i restarted it manually.

[2020-05-26 09:37:51](235.6 50.1 235.6 50.1 1017 1003 020 411 54.10 000 100 0044 00.0 000.0 00.00 00000 00010101 00 00 00000 110
[2020-05-26 09:37:55](236.8 50.1 236.8 50.1 1065 0973 021 411 54.10 000 100 0044 00.0 000.0 00.00 00000 00010101 00 00 00000 110
[2020-05-26 09:37:58](237.5 50.1 237.5 50.1 1092 1014 021 411 54.00 000 100 0044 00.0 000.0 00.00 00000 00010101 00 00 00000 110
[2020-05-26 09:38:01](236.7 50.1 236.7 50.1 1136 0928 022 411 54.00 000 100 0044 00.0 000.0 00.00 00000 00010101 00 00 00000 110
[2020-05-26 09:38:05](237.0 50.1 237.0 50.1 1037 1037 020 411 54.00 000 100 0044 00.0 000.0 00.00 00000 00010101 00 00 00000 110
[2020-05-26 09:38:08](236.2 50.1 236.2 50.1 1157 0934 023 411 54.10 000 100 0044 00.0 000.0 00.00 00000 00010101 00 00 00000 110
[2020-05-26 09:38:11](236.8 50.1 236.8 50.1 1112 0992 022 411 54.10 000 100 0044 00.0 000.0 00.00 00000 00010101 00 00 00000 110
[2020-05-26 09:38:15](237.1 50.1 237.1 50.1 1090 0995 021 411 54.00 000 100 0044 00.0 000.0 00.00 00000 00010101 00 00 00000 110
[2020-05-26 09:38:18](237.7 50.1 237.7 50.1 1069 0963 021 411 54.10 000 100 0044 00.0 000.0 00.00 00000 00010101 00 00 00000 110
[2020-05-26 09:38:21](236.7 50.1 236.7 50.1 1112 0997 022 411 54.00 000 100 0044 00.0 000.0 00.00 00000 00010101 00 00 00000 110
[2020-05-26 09:38:25](236.7 50.1 236.7 50.1 0994 0905 019 411 54.00 000 100 0044 00.0 000.0 00.00 00000 00010101 00 00 00000 110
[2020-05-26 09:38:30](240.5 50.1 000.0 00.0 0000 0000 000 485 54.00 000 100 0044 00.0 000.0 00.00 00000 00000000 00 00 00000 010
[2020-05-26 09:38:34](240.1 50.1 000.0 00.0 0000 0000 000 383 54.00 000 100 0044 00.0 000.0 00.00 00000 00000000 00 00 00000 010
[2020-05-26 09:38:37](240.6 50.1 000.0 00.0 0000 0000 000 273 54.00 000 100 0044 00.0 000.0 00.00 00000 00000000 00 00 00000 010
[2020-05-26 09:38:41](240.7 50.1 000.0 00.0 0000 0000 000 097 54.00 000 100 0044 00.0 000.0 00.00 00000 00000000 00 00 00000 010
[2020-05-26 09:43:26](234.6 50.1 000.0 00.0 0000 0000 000 384 53.40 000 100 0043 00.0 386.0 00.00 00000 00000000 00 00 00010 000
[2020-05-26 09:43:30](235.5 50.1 000.0 00.0 0000 0000 000 426 53.30 000 100 0043 00.1 389.0 00.00 00000 00000000 00 00 00049 000
[2020-05-26 09:43:33](237.8 50.1 237.8 50.1 1403 1319 028 424 53.60 000 100 0043 00.2 381.4 00.00 00000 00010110 00 00 00107 110
[2020-05-26 09:43:36](235.7 50.1 235.7 50.1 1225 1124 024 368 53.30 000 100 0043 00.0 000.0 00.00 00000 00010000 00 00 00000 010
[2020-05-26 09:43:40](236.0 50.1 236.0 50.1 1227 1134 024 368 53.20 000 100 0043 00.0 000.0 00.00 00000 00010000 00 00 00000 010
[2020-05-26 09:43:43](235.1 50.1 235.1 50.1 1223 1135 024 406 53.30 000 091 0043 00.0 000.0 00.00 00000 00010101 00 00 00000 010
[2020-05-26 09:43:47](238.7 50.1 238.7 50.1 0571 0504 011 411 54.40 005 095 0043 00.0 000.0 00.00 00000 00010101 00 00 00000 110
[2020-05-26 09:43:50](236.7 50.1 236.7 50.1 0566 0542 011 408 54.00 001 100 0043 00.0 000.0 00.00 00000 00010101 00 00 00000 110
[2020-05-26 09:43:53](236.0 50.1 236.0 50.1 0566 0538 011 408 54.00 001 100 0043 00.0 000.0 00.00 00000 00010101 00 00 00000 110

 

QFAULT

[2020-05-26 12:04:27] Send: QFAULT
[2020-05-26 12:04:27] [290ms] Return: (08 04 1045 0942 0046 546.8 54.1 236.9 50.14 235.9ﾠ

QFS

[2020-05-26 12:04:35] Send: QFS
[2020-05-26 12:04:36] [390ms] Return: (01 08 04 1045 0942 0046 236.9 50.14 235.9 50.13 000.0 546.8 54.1 044 204ﾕￍ

I have the RAW QPIGS (3-5sec latency, around 25-30k rows per day) log if anyone wants to take a closer look.

[Coulomb]

12 hours ago, StrikerX said:

This might be useful.

Yes, thanks!

I see that early in the log, the utility voltage bumps around the 236 to 237 VAC mark, call it 236.5 V ± 1 V (± 0.4%). Just before the fault, it was 236.7 V; immediately after it was 240.5, a jump of 3.8 V, or 1.6%. That might not seem like much, but when you are balancing power like that, I believe that it is significant.

Also, from the QFS command, the inverter watts were 46 W, though I don't know the sign of this power (does this represent power to or from the utility?). The inverter voltage and frequency are slightly lower than the line (AC-in, utility) voltage and frequency. This suggests to me that the sudden increase in utility voltage caused a surge of power from the utility to the bus, resulting in the rise in bus voltage. 46 W at 460 V is 100 mA, which would charge the bus at I/C = 0.1/(940×10⁻⁶) = 106 V/s.

However, 46 W is also about the idle power of the inverter-charger, so that might be going continuously to the battery to offset the idle power and keep the battery voltage constant (which it was, 54.1 or 54.0 V (you can always get one LSB error) before the fault, and 53.4 V immediately after, when the battery had to provide the idle power on its own.

The battery charge current is given as zero, but unfortunately, it's in whole amps truncated towards zero, and 46 W would be just under one amp, so we can't tell if that all went to the battery or not.

Let's suppose that the idle power was more like 35 W, so 46 W would be 11 W more than needed. Then the excess current that would charge the bus would be about 11/460 (taking 460 V as an "average" bus voltage, chosen earlier to make the maths easier) = 24 mA, which would charge the bus capacitors at 0.024/(940×10⁻⁶) = 26 V/s. That's a fraction short of the amount needed to ramp the bus voltage from 411 V to 547 V in 5 seconds, and we don't know if it was 5 seconds or 1 second.

 So: still not conclusive, unfortunately.

But the jump in utility voltage does seem significant.

Edited May 30, 2020 by Coulomb

[APV]

14 hours ago, Coulomb said:

Yes, thanks!

I see that early in the log, the utility voltage bumps around the 236 to 237 VAC mark, call it 236.5 V ± 1 V (± 0.4%). Just before the fault, it was 236.7 V; immediately after it was 240.5, a jump of 3.8 V, or 1.6%. That might not seem like much, but when you are balancing power like that, I believe that it is significant.

Also, from the QFS command, the inverter watts were 46 W, though I don't know the sign of this power (does this represent power to or from the utility?). The inverter voltage and frequency are slightly lower than the line (AC-in, utility) voltage and frequency. This suggests to me that the sudden increase in utility voltage caused a surge of power from the utility to the bus, resulting in the rise in bus voltage. 46 W at 460 V is 100 mA, which would charge the bus at I/C = 0.1/(940×10⁻⁶) = 106 V/s.

However, 46 W is also about the idle power of the inverter-charger, so that might be going continuously to the battery to offset the idle power and keep the battery voltage constant (which it was, 54.1 or 54.0 V (you can always get one LSB error) before the fault, and 53.4 V immediately after, when the battery had to provide the idle power on its own.

The battery charge current is given as zero, but unfortunately, it's in whole amps truncated towards zero, and 46 W would be just under one amp, so we can't tell if that all went to the battery or not.

Let's suppose that the idle power was more like 35 W, so 46 W would be 11 W more than needed. Then the excess current that would charge the bus would be about 11/460 (taking 460 V as an "average" bus voltage, chosen earlier to make the maths easier) = 24 mA, which would charge the bus capacitors at 0.024/(940×10⁻⁶) = 26 V/s. That's a fraction short of the amount needed to ramp the bus voltage from 411 V to 547 V in 5 seconds, and we don't know if it was 5 seconds or 1 second.

 So: still not conclusive, unfortunately.

But the jump in utility voltage does seem significant.

Just to entertain myself, I added a 10k resistor between the PV input and ground with the unit in bypass.  My multimeter read between 8 and 14mA.  Although I was not able to influence the bus voltage (steady at 373V), I do find it very interesting that the PV input voltage was reported as 110V.  I was actually hoping to simulate wet panels with a leakage to earth, but unfortunately it did not work.  I am not sure whether my leakage current is too low, or too high.  I guess I have to wait for the next big rains and measure the leakage then...

 

[APV]

On 2020/05/30 at 3:25 AM, Coulomb said:

Yes, thanks!

I see that early in the log, the utility voltage bumps around the 236 to 237 VAC mark, call it 236.5 V ± 1 V (± 0.4%). Just before the fault, it was 236.7 V; immediately after it was 240.5, a jump of 3.8 V, or 1.6%. That might not seem like much, but when you are balancing power like that, I believe that it is significant.

Also, from the QFS command, the inverter watts were 46 W, though I don't know the sign of this power (does this represent power to or from the utility?). The inverter voltage and frequency are slightly lower than the line (AC-in, utility) voltage and frequency. This suggests to me that the sudden increase in utility voltage caused a surge of power from the utility to the bus, resulting in the rise in bus voltage. 46 W at 460 V is 100 mA, which would charge the bus at I/C = 0.1/(940×10⁻⁶) = 106 V/s.

However, 46 W is also about the idle power of the inverter-charger, so that might be going continuously to the battery to offset the idle power and keep the battery voltage constant (which it was, 54.1 or 54.0 V (you can always get one LSB error) before the fault, and 53.4 V immediately after, when the battery had to provide the idle power on its own.

The battery charge current is given as zero, but unfortunately, it's in whole amps truncated towards zero, and 46 W would be just under one amp, so we can't tell if that all went to the battery or not.

Let's suppose that the idle power was more like 35 W, so 46 W would be 11 W more than needed. Then the excess current that would charge the bus would be about 11/460 (taking 460 V as an "average" bus voltage, chosen earlier to make the maths easier) = 24 mA, which would charge the bus capacitors at 0.024/(940×10⁻⁶) = 26 V/s. That's a fraction short of the amount needed to ramp the bus voltage from 411 V to 547 V in 5 seconds, and we don't know if it was 5 seconds or 1 second.

 So: still not conclusive, unfortunately.

But the jump in utility voltage does seem significant.

Today it was raining and of course my Error 08 appeared.

First I measured the leakage current into the PV panels.  About 3mA AC per bank (I have 2 banks).

Then I switched off the panels and started logging.  My samples are about 3s apart.

As you can see from the graph, the bus voltage is stable around 372V with the panels off.

At 19:45:04 I switch on the panels and the bus voltage IMMEDIATELY starts to rise.

At 19:45:44, it reaches 465V.  Then I switch off bank 1 of the panels .  The voltage almost stabilises at that point.

At 19:46:01, I swap the 2 banks.  So now bank 1 is active and bank 2 is off.  The voltage continues to rise, but fairly slowly.

At 19:46:20, I switch off both banks again and the bus voltage starts to drop until around 19:48:20 when it stabilises at 372V again.

 

In the meantime, the utility voltage rises and falls a bit, but I find no correlation between the utility voltage and the bus voltage.  All the other parameters are fairly constant as well

 

So if this does not show that the problem is closely related to leakage from the PV panels, I don't know what to think

[charlez]

1 hour ago, APV said:

Today it was raining and of course my Error 08 appeared.

First I measured the leakage current into the PV panels.  About 3mA AC per bank (I have 2 banks).

Then I switched off the panels and started logging.  My samples are about 3s apart.

As you can see from the graph, the bus voltage is stable around 372V with the panels off.

At 19:45:04 I switch on the panels and the bus voltage IMMEDIATELY starts to rise.

At 19:45:44, it reaches 465V.  Then I switch off bank 1 of the panels .  The voltage almost stabilises at that point.

At 19:46:01, I swap the 2 banks.  So now bank 1 is active and bank 2 is off.  The voltage continues to rise, but fairly slowly.

At 19:46:20, I switch off both banks again and the bus voltage starts to drop until around 19:48:20 when it stabilises at 372V again.

In the meantime, the utility voltage rises and falls a bit, but I find no correlation between the utility voltage and the bus voltage.  All the other parameters are fairly constant as well

So if this does not show that the problem is closely related to leakage from the PV panels, I don't know what to think

 

Thanks @APV all in bypass mode?

[APV]

11 hours ago, charlez said:

Thanks @APV all in bypass mode?

@charlez Yes, it goes without saying   I guess I should have mentioned it for completeness sake, but from the beginning of my contribution towards this thread, I have stated that my problems only occur when the unit is in bypass mode...

 

[Coulomb]

17 hours ago, APV said:

As you can see from the graph, the bus voltage is stable around 372V with the panels off.

At 19:45:04 I switch on the panels and the bus voltage IMMEDIATELY starts to rise.

At 19:45:44, it reaches 465V.

Wonderful data, thanks. You saw a 93 V rise in bus voltage over 40 seconds, or 2.3 V/s. If 3 mA AC converts into 3 mA DC into the bus capacitors (that's not obvious to me, and there were two PV strings involved), this would result in

dV/dt = I/C = 3 x 10⁻³ /  10⁻³ = 3 V/s.

Not too far off. But there are two strings, and it looks by your other results that they are not always additive. It could well depend on where along the string the leakage(s) is(are).

So this is totally believable, if the firmware makes no attempt to regulate the bus voltage. Perhaps the problem is that the PV current measurement is relatively course, perhaps at 1 A or 0.1 A resolution. Then a slow leakage current would be "invisible" to the algorithm, and it would be "ambushed" by the slow leak. During the day, errors due to the measurement resolution might average out to zero.

It should be possible to alter the algorithm to check the bus voltage rather than relying on balancing the PV and load currents. So now it's a matter of making the appropriate engineer at Voltronic Power aware of the problem, and convincing them that it's worth fixing and releasing an updated firmware.

Before you ask, it's way too complex for me to design a fix and implement it as a patch, without a machine to test on.

Edited June 11, 2020 by Coulomb
Damned keyboard or touchpad is injecting newlines...

[charlez]

Thanks @APV and @Coulomb. Impressive skills. With my setup if it's rains and there is PV voltage, with some current, in bypass mode, the bus voltage stays stable. This changes at sunset as I experienced today. Good all day, then, with the onset of evening, a crash with 08 error.

[maxo]

Hello to all included in this debate about Error 08

I'm coming back here to this forum after few years (last time back in 2017), when I have need to changed main board due to malfunction around TX6 and parts around.

I have Axpert MKS 5kVA_4kW, 48V, max 145VDC from PV, 3000MPPT, produced back in year 2013 or maybe 2014.

I believe software and also hardware in my case is different than in case described here for MKS II 5kW, but fault 08  means the same = bus voltage to high.
I read all what is said here and also on some other related forums about fault 08 on Axpert's.
My PIP operates with utility 230V, 50 Hz (utility voltage varies between 230 to max. 242V and frequency varies between 49,6 to 50,2 Hz.)
My setup is follows:
(battery off at 46V - back to utility supply, battery charge during the night at 2A), bypass operation during the night, in the morning PV panels and/or utility supply up to moment when battery  reach 52V, then bypass off and operation from PV and battery , followed buck charge up to 58,4V and then charge go down to 54V or 53,9V and then happened error 08 very soon, but only in case described in next sentence.

Namely in my case, error 08 started aprox.1 month ago (never before in past years), it's happened only during the very sunny day and PIP operates from PV with battery charge (4*12 V lead acid battery, 180 Ah)  and load's supply in the house. On days when is there more diffuse light or partly cloudy day, we never encountered error 08 (nor during the day, nor during the night, nor during the rain period). But error 08 happen only in case (battery at 54V) and the load in house is small (less than 20%).

From my observations, software bug mybe is not the case here (it works 6 years without error 08), more real possible reason is hardware malfunction, maybe leak capacitors, changed value of resistors on OP-AMP,  maybe cold connection somewhere or etc.  
If I look StrikerX log, his battery was also very close to 54,0V and at low load (10-20%) every time, when error 08 comes out.

Maybe is good to thought abut that situation, namely when charge of the battery is higher what is really needed to sustain at 54,0V - This is similar what thought about Coulomb , some part of excess energy must go somewhere and could possible over charge 2 capacitors on bus to near or even over 500V, as could we see from logs (it's rise could be very rapid).

Sorry I do not have yet the final solution what to do in my case, I just thought to wait a bit, maybe we could all together find the real reason for error 08,  besides seem's not to be the same in all cases here. 

maxo

[Coulomb]

8 hours ago, maxo said:

I have Axpert MKS 5kVA_4kW, 48V, max 145VDC from PV, 3000MPPT

OK, so that's a very different situation to what this topic is about, the Axpert MKS II models with the un-isolated high voltage Solar Charge Controllers. Your SCC charges the battery directly. The only way that it can influence the bus voltage is if the battery voltage rises very high.

8 hours ago, maxo said:

But error 08 happen only in case (battery at 54V) and the load in house is small (less than 20%).

So it sounds like it happens when the battery is floating (at 54 V or 13.5 V per nominally 12 V module) and with light AC loads. My guess is that your battery is getting old and hence high internal resistance. When the battery is full, its internal resistance is relatively high. That means that small changes in charge or discharge current can cause large changes in the battery terminal voltage. Generally, the bus voltage will sit at around 8 times the battery voltage when in battery mode (for your model; for some newer models, it's 7 times). But for the bus voltage to get high enough for a fault code 08, which is 500 V, the battery voltage would have to be at 62.5 V (15.6 V per nominally 12 V module). This seems very unlikely.

I think the first thing to check is that the bus voltage really is exceeding 500 V. Is it possible to monitor it with a command such as QPIGS? Or can you see it on your monitoring software? Or use QFS or QFAULT to display the bus voltage after an error 08?

[APV]

On 2020/06/11 at 9:03 PM, charlez said:

Thanks @APV and @Coulomb. Impressive skills. With my setup if it's rains and there is PV voltage, with some current, in bypass mode, the bus voltage stays stable. This changes at sunset as I experienced today. Good all day, then, with the onset of evening, a crash with 08 error.

@charlez has pointed me to this information from the official Axpert MKS II manual:

14. WARNING: Because this inverter is non-isolated, only three types of PV modules are acceptable: single crystalline, poly crystalline with class A-rated and CIGS modules. To avoid any malfunction, do not connect any PV modules with possible current leakage to the inverter. For example, grounded PV modules will cause current leakage to the inverter. When using CIGS modules, please be sure NO grounding.

This corresponds to my findings that a large percentage of the Error 08 problems are related to the design of the inverter.  In other words, when in bypass mode, the PV input must have no leakage to earth, else the bus voltage just rises until it trips.

So I have constructed an automatic isolator.  It disconnects the PV panels when they deliver less than 70V.  By that time, my inverter has long gone into bypass.  The PV panels are reconnected when they generate more than 15W (and the voltage is higher than 70V).  I call it the Error 08 Buster

I tried to keep it as simple as possible.  It works really well.  I had to use the bulb (microwave oven lamp) to prevent the relay from being activated before the panel can generate enough power (not voltage).  Without the bulb (dummy load), the relay turns on and off every 2 seconds in the morning before sunrise.  

These components cost around R500, which I think is a bargain considering how much frustration this problem has been causing me.  Someone even described it as "worse than load shedding" ...

  Today we had rain, but not too much.  Not sure if anyone else in the Cape Town area experienced the error, or are going to experience it tonight, but I won't.  (I hope!!!!)

 

[charlez]

Thanks @APV, pity my supplier didn't disclose this issue when I was sold the kit. Please share components needed. Thanks Charles.

[APV]

9 hours ago, charlez said:

Thanks @APV, pity my supplier didn't disclose this issue when I was sold the kit. Please share components needed. Thanks Charles.

@charlez - I don't think the suppliers are even aware of this issue with the inverter!

Here is the circuit

The heart of the isolater, is the LD03-16B12 (AC/DC Converter Vin = 90-528VAC (100-745VDC) Vout = 12V 250MA).  Since I have 2 banks of panels consisting of 400W panels capable of delivering more than 20A in total, I had to use a 30A relay.  If you have smaller panels, you can use a smaller relay.  Just make sure that the coil resistance of the relay is more than 70 Ohms to limit the current draw from the AC/DC converter.

Of course you can also use any other type of DC/DC (or AC/DC) converter.  As long as it can handle a relatively high input voltage with an output current of around 250mA at 12V (Or whatever voltage you desire to trigger the relay)

I hope this is useful for everybody who experiences Error 08 while the PV panels are very wet and the inverter is in bypass mode...

[Cirrus]

On 2020/04/09 at 3:53 PM, Coulomb said:

My initial thought was that they had ported the PylonTech battery type == PYL code to this machine. Alas, no.

There is a new command QBMS, which spits out data like BMS battery voltage, maximum charge current, and so on.

This information comes from parsing a new command of the form ^DnnnBMSddd... where nnn is the length of the command, just like a device response from a "secure" command (ones that start with the up-arrow). This seems to use the serial port that is otherwise unused in these models with 450 V max Solar Charge Controllers. That serial port is used to talk to the processor on the Solar Charge Controller in 145 V max SCC models; in the 450 V max SCC models, the DSP controls the PV boost converter directly, and so doesn't need the second serial port.

The maximum charge current value (and likely other values) seems to be actually used; in the case of maximum charge current, it is used instead of the EEPROM maximum charge current setting, if appropriate bits are set. Presumably those bits indicate that the BMS is connected and BMS data is actively being received.

I note that the Pylontech BMS information is in a packet that starts with an up-arrow, but as far as I can tell, the format is different. So this is not directly for PylonTechs. So what is it for? A great question. My wild guess is that Voltronic Power are developing some new interface for battery BMSs, separate from the inverter-chargers themselves, which might translate BMS data from various different battery BMSs into one format, the one indicated above. But I stress that this is a wild guess. I'm further guessing that it's not quite ready yet, but the firmware source code is in the process of incorporating this new functionality, and when a fix for the bus voltage control / error 08 bug was needed, this BMS stuff "came along for the ride".

So while this new BMS code isn't a port of the battery type == PYL code, it might even be something better.

As for what they changed in the way of bus voltage control, I've not found that code as yet. There are plenty of red herrings: variables and functions with "busv" in the name, but aren't used. I may get to it tomorrow my time; I'm curious as to what they've done. With all the BMS code additions, it's not a simple matter of comparing function lengths to see where significant changes have occurred.

Hi Everyone

are not these commands for the BMS box that is apparently available from RCT as Rectron has a RCT-Axpert BMS box that is apparently made by Voltronic for Axpert MKS2 with the latest firmware that connects to the Modbus on the Inverter.

[Coulomb]

17 hours ago, Cirrus said:

are not these commands for the BMS box that is apparently available from RCT as Rectron has a RCT-Axpert BMS box that is apparently made by Voltronic for Axpert MKS2 with the latest firmware that connects to the Modbus on the Inverter.

Interesting. I've not seen any details, and a quick search revealed not even a photo or what it's supposed to do. You you have a link with details?

[Cirrus]

4 hours ago, Coulomb said:

Interesting. I've not seen any details, and a quick search revealed not even a photo or what it's supposed to do. You you have a link with details?

Hi Coulomb

I do have the manuals for it

Modbus Duo Box(Monitor&BMS)-manual.pdf

[Coulomb]

4 hours ago, Cirrus said:

I do have the manuals for it

Thanks. Strange that they make you use an RS-485 to RS-232 (or RS-485 to TCP/IP) converter to talk to the PC.

Annoying that they don't say what version firmware you need to talk to this thing. Or what battery it will talk to. I'm guessing that it only talks to the Pylontech, so this is for models like the MKS II that don't have an RS-485 port. In fact, all models apart from Kings and VM IIIs. It seems that it will only work with 5 kW models, so it looks like only those models' firmware will get the new command.

To answer your earlier question, yes, it seems to me that they must be using the new command to talk to this box. (Again, they don't say how it works, presumably so as not to help the clone makers). So firmware updates will be required for older models, and we know the trouble getting hold of those.

Edit: however, my guess about using the spare RS-232 port on the models with 450 V or 500 V max SCCs looks to be wrong. I'd say that this box intersperses the BMS command within commands from the PC to the inverter. Most commands will work from either RS-232 port just as well. So this should work for Axpert MKS models, not just those with 450 V or 500 V max SCCs.

Edited June 26, 2020 by Coulomb

[Coulomb]

On 2020/04/09 at 11:53 PM, Coulomb said:

There is a new command QBMS, which spits out data like BMS battery voltage, maximum charge current, and so on.

This information comes from parsing a new command of the form ^DnnnBMSddd... where...

Perusing the recent Axpert King firmware 71.92, I note that it has new BMS commands (QBMS and PBMS), but nothing like the above. So it's quite possible that the above was abandoned, or evolved into the newer QBMS/PBMS commands.

Surely the MKS II and King commands aren't going to diverge. Would they? 

[Denarius]

On 2020/06/21 at 6:52 PM, APV said:

@charlez has pointed me to this information from the official Axpert MKS II manual:

14. WARNING: Because this inverter is non-isolated, only three types of PV modules are acceptable: single crystalline, poly crystalline with class A-rated and CIGS modules. To avoid any malfunction, do not connect any PV modules with possible current leakage to the inverter. For example, grounded PV modules will cause current leakage to the inverter. When using CIGS modules, please be sure NO grounding.

Hi @APV, I'm probably missing something, but I can only find that in the Axpert VM II and not the Axpert MKS II manual.  I searched through various manuals of different brands.

I'm interested in this topic because my father is experiencing the same issue reported here.  It was raining, he was on grid for a long time, then a few hours after dark everything shut down and he received error 08.  It's never happened again, but it hasn't really rained since he bought the inverter.

[APV]

10 hours ago, pierre. said:

Hi @APV, I'm probably missing something, but I can only find that in the Axpert VM II and not the Axpert MKS II manual.  I searched through various manuals of different brands.

I'm interested in this topic because my father is experiencing the same issue reported here.  It was raining, he was on grid for a long time, then a few hours after dark everything shut down and he received error 08.  It's never happened again, but it hasn't really rained since he bought the inverter.

@Pierre

You are correct - that very important piece of information is not present in all user manuals for this type of inverter.  However, irrespective of the brand, if it can handle 450V Solar panels, it probably is of the same design.

As I have proven (at least in my case), if there is some leakage to earth  and the inverter goes into bypass mode, Error 08 will occur.

After I have installed the automatic isolation circuit that I have described earlier in this forum, I have not experienced that error again (Touch Wood).  Not even during the heavy rains of the last couple of weeks.

So if you cannot complete isolate the PV panels from one another AND from ground (Plastic mountings???), I guess you will experience this very inconvenient problem.  Unless of course you use another type of inverter, or you use an auto / manual isolation of the PV panels in bypass mode.

Regards

A