APV

In the user manual of the Axpert SOL-I-AX-8M, the following is stated on page 47: Note: Parallel feature will be disabled when only PV power is available Does this actually mean, that even if I have batteries connected to it and the Utility power is switched off, that I cannot use more than one in parallel? Or does it simply mean that I cannot use the parallel function without both Utility AND batteries? I know from experience that the older 5kW models use the battery leads to share the parallel current and obviously to keep the outputs. Has anyone actually tested this scenario?

Yes, your statement is 100% correct, IF you interrupt the DC from the PV panels under full load. However, in this scenario, the PV panels are disconnected when they are delivering very low power... Nice demonstration though

If you are considering using a Sonoff switch, you will have to change the wiring a bit. I am sure you can do it!!! If you use a Sonoff and a contactor (230VAC coil), it will look as follows: If you prefer to use a relay with 230VAC coil, it would look as follows:

I do not think a Sonoff switch will work, since it only breaks one of the 2 wires. You will still have leakage to earth via the other (unbroken) PV wire. I really think you need to find a device that has a double pole relay built into it so that you can break both wires coming from the solar panels. Alternatively, you can use the Sonoff to control a double pole relay with a 240V coil. That setup will isolate the PV panels completely as well.

If the problem disappears when you disconnect your panels, you need to build an auto-isolator like I designed and posted - that was the only solution that worked for me. It is only applicable to the following situation: <SPAN STYLE='background:dddd00;'> 1. Inverter in bypass mode AND 2. Solar panels are wet. </SPAN> Regards A

Firstly, are you using the model with the very high PV input (up to 450V)? The circuit will only work for these models with PV panels attached. As @Coulomb has mentioned (more than once), the problem can also occur when the battery voltage is too high. Have you taken any measurements when you ran into error 08?

Yes, the large capacity panels (330W+) are all poly crystalline. Mono would be too expensive...

Hallo @charlez Good job! Have you watched it working around 18h15 and 07h15 (depending on the sun)? I especially like the morning startup where the bulb first starts glowing and then the relay kicks in, the bulb goes off and the inverter switches to solar... Your wires exiting the board on the left top side, look a bit thin to me. Remember that the solar panel current flows through all these wires. For 20A, you should use at least 2.5mm². Maybe your wires are that thick and it is just the photo making them look rather thin? Of course the current will only be high when your panels are delivering maximum power, in other words in bright sunlight and the inverter delivering maximum power...

I would suggest that you replace the PV breaker by a PV isolator in any case - it is just good practise. Breaking only 1 wire to the PV panels does not prevent the AC leakage current from flowing from the inverter via the PV panels to earth. The good news is that I believe that my circuit will work for you then.

Is it an isolator (breaking BOTH wires), or breaker (only breaking 1 wire)? You need to completely isolate the panels to prevent Error 08. If you already have an isolator in place, then my circuit is not going to help you, since it only isolates the PV panels. What is very interesting to me, is that your unit keeps on resetting. Mine only did it 3 times and then complete shut down...

Good. So then the circuit should solve your problem. Let me know how it goes...

Hallo @Classna Bypass mode is when the inverter does not run off batteries (or solar), but only from the Utility power....

@Classna You can replace the LD03-16B12 with one of the following: LD10-26B12, or LD20-26B12 The distributors for Mornsun in Australia, are: DLPC Pty Ltd （Australia & New Zealand） Tel: 61 7 3823 4844 FAX: 61 7 3823 4866 E-mail: [email protected] Website: www.dlpc.com.au Fairmont Marketing(Victoria) （AUSTRALIA） Tel: 03 9878 3077 FAX: 03 9878 4522 E-mail: [email protected]

Hallo @Classna I presume you are located in Australia??? Have you experienced the same issues? Error 08 while the inverter is in bypass and it is raining? I found the AC-DC converter on Alibaba as well: https://www.alibaba.com/showroom/ld03-16b12.html?fsb=y&IndexArea=product_en&CatId=&SearchText=ld03-16b12&isGalleryList=G Maybe you can order from them. You can replace it by any AC-DC converter block. The input must be able to handle up to 440V AC (700V DC) and have an output voltage of 12v and a minimum output current of 250mA . The output voltage can be higher, but then you will need to use another relay and Zener diode. So I guess it will be much simpler for you to just stick to the diagram.

Hallo @Classna You can find the relay at Aliexpress at https://www.aliexpress.com/item/32835375697.html?spm=a2g0o.productlist.0.0.e8d73424MccJGE&algo_pvid=7aedc1e2-263b-4d06-af6e-a4b34421831d&algo_expid=7aedc1e2-263b-4d06-af6e-a4b34421831d-23&btsid=0be3743615958382138547685e0790&ws_ab_test=searchweb0_0,searchweb201602_,searchweb201603_ I cannot find the AC-DC converter at Aliexpress though As @charlez has mentioned, it is widely available, e.g. https://www.edgeelectronics.com/ac-dc-converters/ld03-16b12/ I am also uploading the schematic again - the capacitor values were displayed incorrectly!

Hallo @charlez Why 40A? A 335W panel has a short circuit current of less than 10A. With 2 strings, you need less than 20A. I am using 405W panels (7x2) and used a 30A relay. You can get a 30A from Communica - https://www.communica.co.za/products/jqx30f-2z-dc12v-flange I also got the DC-DC converter from them JQX30F-2Z-DC12V FLANGE Relay • Flange • Form 2C • VCoil= 12V DC • IMax Switching= 30A • RCoil= 96Ω • 6.3mm Terminal SKU: JQX30F-2Z-DC12V FLANGE BRAND: Asiaon IN STOCK R 152.38 (inc VAT)

@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

@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...

@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 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...

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

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...

@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) ???

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...

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).