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Axpert MKS II 5kW Error 08


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@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

I did put up a fuss with Voltronic themselves regardings this issue.  At first they gave me a lame answer as follows : "Per your information below, it means error 08 was caused by the surge from

@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 cryst

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  • 2 weeks later...

I have encountered another issue.  Every time it rains, the earth leakage unit on my house DB trips.  This morning when it did it, I measured the AC voltage between ground and the PV input - 130VAC!!!!

The source of the floating voltage is the inverter, not the panels. 

Why would this happen?  I thought the PV input was 100% isolated from the rest of the circuit!!!  This is probably part of my problems with the Error 08 issue...

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11 hours ago, APV said:

I thought the PV input was 100% isolated from the rest of the circuit!!!  This is probably part of my problems with the Error 08 issue...

No, none of the solar charge controllers are isolated. The only isolation is between the battery and the DC bus. So for the 145 V max SCCs, they get isolation from the AC-out because they connect to the battery. But Axpert MKS IIs (as discussed in this topic) have a boost converter that connects directly to the DC bus. So you'll see chopped 230 V on the panel wires (with the high frequency component attenuated a little by a common mode choke). So you must be getting leakage from some panel wire / connector / inline fuse / panel junction box) to earth when it rains, causing the trip.

Huh. Who said Axpert MKS IIs don't have insulation monitoring? 😮  Of course, if it was proper insulation monitoring, it presumably could just show a warning and disconnect the PV, rather than black out the whole house. Though I'm not certain that the MKS II SCCs have a relay that can disconnect their output from the DC bus. [ Edit: it looks like there isn't. Sigh. ]

Edited by Coulomb
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5 hours ago, Coulomb said:

No, none of the solar charge controllers are isolated. The only isolation is between the battery and the DC bus. So for the 145 V max SCCs, they get isolation from the AC-out because they connect to the battery. But Axpert MKS IIs (as discussed in this topic) have a boost converter that connects directly to the DC bus. So you'll see chopped 230 V on the panel wires (with the high frequency component attenuated a little by a common mode choke). So you must be getting leakage from some panel wire / connector / inline fuse / panel junction box) to earth when it rains, causing the trip.

Huh. Who said Axpert MKS IIs don't have insulation monitoring? 😮  Of course, if it was proper insulation monitoring, it presumably could just show a warning and disconnect the PV, rather than black out the whole house. Though I'm not certain that the MKS II SCCs have a relay that can disconnect their output from the DC bus. [ Edit: it looks like there isn't. Sigh. ]

It is very likely that the panel wires get wet.  The connectors between the panels are currently just lying on the roof.  Even though they are supposed to be waterproof, there probably is a bit of leakage when the roof gets wet.  So firstly, I shall have to try and lift the connectors off the roof, where possible.  If that does not solve the problem, I guess I shall have to build a 1:1 isolation circuit myself :)  

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1 minute ago, charlez said:

Hi @APV  I must confess I also took a short-cut and my pv wires are also just lying on the roof. Do you think that if I cable tie them to the rails that would be good enough? By the way they these are the panels: 330 WATT POLY CANADIAN SOLAR PANELS

Hallo @charlez I believe that simply lifting them from the surface of the roof with cable ties (or whatever) should be fine.   It will be quite a mission for me to modify my wiring, since I have grouped the panes in a chunk of 8x2 with only a 1cm gap between them.  Hopefully I can reach the cables from the lower and upper sides of the array...

 My problems only occur in fairly heavy rains.  I use the CANADIAN SOLAR 405W SUPER HIGH POWER POLY PERC HIKU panels with MC4 connectors, so it is the same brand...

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1 hour ago, APV said:

 My problems only occur in fairly heavy rains.  I use the CANADIAN SOLAR 405W SUPER HIGH POWER POLY PERC HIKU panels with MC4 connectors, so it is the same brand...

Hello guys...

My problem is the same as yours when it rains. My panels is Canadian Solar 315W Poly. It's just a coincidence or there is a problem with Canadian Solar.

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10 hours ago, charlez said:

No water and crashed with the 08 error after being on bypass for a few hours.

That is bad news @charlez :(  If (and only if) moisture is part of the problem, it could be that the cables were not completely dry after laying on the roof. So maybe there still was some leakage in your case... I have to tie mine up like you did in any case, since rain causes my earth leakage to trip.  So my system is even worse than yours :)

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@APV was hoping this was the problem. The way I see it now is:

  • Does not seem to be leakage because of poor wiring protocol.
  • Could be a problem with Canadian Solar with water ingress.
  • Not a specific earthing problem with my setup. I have earthed the panels to a panel specific earth spike.
  • My PV panels are isolated via a DC breaker and surge protector.

All this still points to the Axpert, most likely firmware but obviously could be hardware. Even is the panels had an internal issue the leakage should be isolated and not cause a high bus voltage issue, but this is something I know very little about.

 

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9 minutes ago, charlez said:

@APV was hoping this was the problem. The way I see it now is:

  • Does not seem to be leakage because of poor wiring protocol.
  • Could be a problem with Canadian Solar with water ingress.
  • Not a specific earthing problem with my setup. I have earthed the panels to a panel specific earth spike.
  • My PV panels are isolated via a DC breaker and surge protector.

All this still points to the Axpert, most likely firmware but obviously could be hardware. Even is the panels had an internal issue the leakage should be isolated and not cause a high bus voltage issue, but this is something I know very little about.

 

Unfortunately the PV input of the Axpert is not isolated as @Coulomb pointed out.  So this means any leakage to earth on the panels, whether through connectors or the panels itself, can be a contributing factor towards our problems.  However as @JustinSchoeman pointed out, it definitely is not the only factor.  He uses the Axpert as a UPS only, so there are no panels involved!!!  I hope his setup is the exception to the rule.  The earth leakage issue does seem to be very relevant in the other cases, since you ( @charlez ) have also managed to prevent further occurrences of Error 08 by simply isolating the panels (after the first occurrence of the error).

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I have a simple and stupid solution for error 08. Because I can monitor the bus voltage from my inverter, I made a code in my Home Assistant that will change the inverter to SBU if the bus voltage is more than 480 V. And that has saved me from error 08 several times.

Screenshot_20200527-062307_Chrome.thumb.jpg.a3017db2eaa55f45380877a4872c5e8e.jpgThis is my bus voltage yesterday, when it rained the bus voltage rose several times. 

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5 minutes ago, rddkrn said:

I have a simple and stupid solution for error 08. Because I can monitor the bus voltage from my inverter, I made a code in my Home Assistant that will change the inverter to SBU if the bus voltage is more than 480 V. And that has saved me from error 08 several times.

Screenshot_20200527-062307_Chrome.thumb.jpg.a3017db2eaa55f45380877a4872c5e8e.jpgThis is my bus voltage yesterday, when it rained the bus voltage rose several times. 

@rddkrn thanks for this. Something I have been wanting to do. Would you mind sharing your code? Is it Python?

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Hi all, thought I would share this.

Spent whole day on bypass, rainy day with very little power generated.

image.thumb.png.55ff11e72e153d14dc9a00301caff08c.png

PV panels connected, bus voltage has risen to 480V at about 17:30.

================ Status ==================
Parameter                     	Value           Unit
ac_input_frequency            	49.8            Hz
ac_input_voltage              	226.6           V
ac_output_active_power        	0992            W
ac_output_apparent_power      	1065            VA
ac_output_frequency           	49.8            Hz
ac_output_load                	021             %
ac_output_voltage             	226.6           V
battery_capacity              	057             %
battery_charging_current      	000             A
battery_discharge_current     	00000           A
battery_voltage               	49.90           V
battery_voltage_from_scc      	00.00           V
bus_voltage                   	480             V
inverter_heat_sink_temperature	0031            Deg_C
is_ac_charging_on             	0               True - 1/False - 0
is_battery_voltage_to_steady_while_charging	0               True - 1/False - 0
is_charging_on                	0               True - 1/False - 0
is_configuration_changed      	0               True - 1/False - 0
is_load_on                    	1               True - 1/False - 0
is_sbu_priority_version_added 	0               True - 1/False - 0
is_scc_charging_on            	0               True - 1/False - 0
is_scc_firmware_updated       	0               True - 1/False - 0
pv_input_current_for_battery  	0000            A
pv_input_voltage              	000.0           V
unknown_value_in_byte_response	010  

PV panels disconnected, bus voltage drops

================ Status ==================
Parameter                     	Value           Unit
ac_input_frequency            	49.8            Hz
ac_input_voltage              	227.7           V
ac_output_active_power        	1042            W
ac_output_apparent_power      	1161            VA
ac_output_frequency           	49.8            Hz
ac_output_load                	023             %
ac_output_voltage             	227.7           V
battery_capacity              	057             %
battery_charging_current      	000             A
battery_discharge_current     	00000           A
battery_voltage               	49.90           V
battery_voltage_from_scc      	00.00           V
bus_voltage                   	442             V
inverter_heat_sink_temperature	0031            Deg_C
is_ac_charging_on             	0               True - 1/False - 0
is_battery_voltage_to_steady_while_charging	0               True - 1/False - 0
is_charging_on                	0               True - 1/False - 0
is_configuration_changed      	0               True - 1/False - 0
is_load_on                    	1               True - 1/False - 0
is_sbu_priority_version_added 	0               True - 1/False - 0
is_scc_charging_on            	0               True - 1/False - 0
is_scc_firmware_updated       	0               True - 1/False - 0
pv_input_current_for_battery  	0000            A
pv_input_voltage              	000.0           V
unknown_value_in_byte_response	010      

Thanks

Charles

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On 2020/05/15 at 4:52 PM, APV said:

I can confirm that my unit also shutdown in the early morning hours.  It was raining then.

 

On 2020/05/26 at 12:36 AM, charlez said:

This morning got Error 08 again after some rain.

 

On 2020/05/26 at 6:50 PM, charlez said:

Hi @APV  I must confess I also took a short-cut and my pv wires are also just lying on the roof. 

 

On 2020/05/26 at 6:59 PM, APV said:

 My problems only occur in fairly heavy rains. 

 

On 2020/05/26 at 8:56 PM, rddkrn said:

My problem is the same as yours when it rains.

 

On 2020/05/26 at 9:21 PM, rddkrn said:

Laying on the roof. 

I've been thinking about a mechanism for this. When in battery mode (i.e. the inverter proper is powering loads), the bus connects alternately connects right way up and upside down at 100 changes per second. It also switches on and off (floating) at IGBT switching frequency (~38 kHz) to make the sine wave, but that gets smoothed out by the common mode choke at the PV panel connections. So there are times when the neutral output (which is about the same potential as earth) is more positive than the negative end of the DC bus (the reference for the PV boost converter), at times by more than 300 V. If this leaks to the PV input that isn't referenced to DC bus negative, then up to 300 V is available to the boost converter input. This is well over the 120 V minimum start voltage, so it starts operating the boost converter. There is little current available, but the MPPT knows how to extract the maximum power from it, and boost that to the present bus voltage.

If the load happens to be low, it might be possible to power the load and a little bit more; the little bit more has nowhere to go other than to charge the bus capacitors to higher and higher voltage. But in @charlez's example above, the output power is 992 W when the bus voltage hit 480 V. I can imagine perhaps 100 mA at an average of say 200 V leaking into the PV input, but that's only 20 W. So what might be happening is that somehow the bulk of the load power is supplied by the battery, and the PV power (which the control system is not expecting) is only supplying the difference between load power and power from the battery-to-bus DC-DC converter. As I type this, it seems pretty unlikely, unless it's some sort of overshoot thing, where water suddenly creates a significant path where there was none before, and the sadly too common overshoot that Axperts are prone to is what triggers the fault code 08. Even that seems a bit far fetched.

In Charlez's graph, the load power does seem low at the right hand end, so maybe the load was very low (< 20 W) until just before the bus voltage hit 480 V, and perhaps a fridge startup or other load just happened to come on at the time of the sample. Again, it seems a bit of a stretch.

Can anyone dig into their logs and either support or shoot down at least the very low load theory?

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Thanks @Coulomb. I have a 350w pump that runs 24/7 so unlikely that the load dropped below that. I do have a 1hp pump supplying water to the house connected and fridge connected.

These are the defining features of the problem as I see them:

  • Load around 15%
  • No PV voltage
  • But PV breaker connected
  • Bypass mode
  • Moisture on panels
  • Been in bypass mode for quite a while, multiple hours

Rained the whole night on and off. Disconnected the panels and the unit stayed up all night. Still raining but panels producing some power at 1 or 2 amps. Bus voltage stable.

================ Status ==================
Parameter                     	Value           Unit
ac_input_frequency            	49.9            Hz
ac_input_voltage              	232.5           V
ac_output_active_power        	0666            W
ac_output_apparent_power      	0697            VA
ac_output_frequency           	49.9            Hz
ac_output_load                	013             %
ac_output_voltage             	232.5           V
battery_capacity              	057             %
battery_charging_current      	002             A
battery_discharge_current     	00000           A
battery_voltage               	49.90           V
battery_voltage_from_scc      	00.00           V
bus_voltage                   	372             V
inverter_heat_sink_temperature	0033            Deg_C
is_ac_charging_on             	0               True - 1/False - 0
is_battery_voltage_to_steady_while_charging	0               True - 1/False - 0
is_charging_on                	0               True - 1/False - 0
is_configuration_changed      	0               True - 1/False - 0
is_load_on                    	1               True - 1/False - 0
is_sbu_priority_version_added 	0               True - 1/False - 0
is_scc_charging_on            	1               True - 1/False - 0
is_scc_firmware_updated       	0               True - 1/False - 0
pv_input_current_for_battery  	0002            A
pv_input_voltage              	130.0           V
unknown_value_in_byte_response	010  

 

Need to put that script together to monitor bus voltage.

 

 

 

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5 hours ago, Coulomb said:

I've been thinking about a mechanism for this. When in battery mode (i.e. the inverter proper is powering loads), the bus connects alternately connects right way up and upside down at 100 changes per second. It also switches on and off (floating) at IGBT switching frequency (~38 kHz) to make the sine wave, but that gets smoothed out by the common mode choke at the PV panel connections. So there are times when the neutral output (which is about the same potential as earth) is more positive than the negative end of the DC bus (the reference for the PV boost converter), at times by more than 300 V. If this leaks to the PV input that isn't referenced to DC bus negative, then up to 300 V is available to the boost converter input. This is well over the 120 V minimum start voltage, so it starts operating the boost converter. There is little current available, but the MPPT knows how to extract the maximum power from it, and boost that to the present bus voltage.

If the load happens to be low, it might be possible to power the load and a little bit more; the little bit more has nowhere to go other than to charge the bus capacitors to higher and higher voltage. But in @charlez's example above, the output power is 992 W when the bus voltage hit 480 V. I can imagine perhaps 100 mA at an average of say 200 V leaking into the PV input, but that's only 20 W. So what might be happening is that somehow the bulk of the load power is supplied by the battery, and the PV power (which the control system is not expecting) is only supplying the difference between load power and power from the battery-to-bus DC-DC converter. As I type this, it seems pretty unlikely, unless it's some sort of overshoot thing, where water suddenly creates a significant path where there was none before, and the sadly too common overshoot that Axperts are prone to is what triggers the fault code 08. Even that seems a bit far fetched.

In Charlez's graph, the load power does seem low at the right hand end, so maybe the load was very low (< 20 W) until just before the bus voltage hit 480 V, and perhaps a fridge startup or other load just happened to come on at the time of the sample. Again, it seems a bit of a stretch.

Can anyone dig into their logs and either support or shoot down at least the very low load theory?

My unit has also raised error 08 under medium load conditions.  I was watching TV and the fridge was running.  I do not have the log, but I estimate the load to be around 600W at that stage.

I have measured the bus voltage with a multimeter one day after heavy rains just after the unit went into bypass.  The kettle was on at that stage => 2000W load.  The bus voltage started climbing quite fast.  When it reached 470V, I disconnected the panels and the voltage returned to 372V within 30 seconds.

So my conclusion is that this condition is not dependant on the load...

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