Axpert Error 51 repairs

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johnnyZA
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Axpert Error 51 repairs

Post by johnnyZA »

Axpert VM 5KW

So I ran into the dreaded Error 51 late last night. My system is 100% off-grid, with no mains connected. It gave error 51 and disconnected the output.

I have completely disconnected the db board from its output, as well as the solar panels from its input, leaving only the battery bank connected to the inverter. Since the error still occurred, I also disconnected the batteries and tried using only one different set of batteries at a time. Every time the error comes back. It stays on for between 5 and 90 minutes. I also confirmed that it's not clogged up with dust and that the fans still work and turn on while in use.

At this stage I'm fairly certain that the issue is with the inverter hardware itself, but testing and troubleshooting the hardware myself is far outside of my skillset. From what I've read here and on powerforums, its often less expensive to buy a new inverter than to replace the board.

I know this is an Aus site, but found so many SA users here that it might be worth asking: does anybody know of a person or company in Cape Town that is able to test/repair these inverters? Its less than 2 years old, so replacing it so soon feels like a terrible waste.
tahir
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Re: Axpert Error 51 repairs

Post by tahir »

Dear check your battery voltage.
Is there same voltage on inverter display and on volt meter?
johnnyZA
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Re: Axpert Error 51 repairs

Post by johnnyZA »

Update: I no longer have the error 51 issue. It looks like it was caused by heat.

To fix the issue, I reversed the fans inside the inverter, so they now blow in the direction printed on the pc board. I also added an external fan at the top right and power it from the "fan 3" connection on the pc board. Now there are zero issues, and I assume the inverter is running a lot cooler, because the fans turn on a lot less and make a lot less noise :D
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Re: Axpert Error 51 repairs

Post by johnnyZA »

Another update: Reversing the fans allowed it to keep working without issue for 14 months, and now the error is back. Occasionally Error 08 will cause it to shutdown, but usually it is error 51. It started again on a very hot day (40deg C outside) with batteries full and a load of about 800w.

Almost every day between 1pm and 2pm. If I leave the panels disconnected during that time, it does not shut down. Normal voltage from the panel during that time is around 120V. I have not seen what the voltage is when it goes off.

On Saturday, it kept giving the issue every few minutes, so I left it off for a few days. After reconnecting it again it worked for 2 days without issue. Now it seem to be back to its routine once or twice per day.

However, I have noticed that, while error 51 is displayed and I turn the output off and disconnect the panels, the voltage stays high for a few seconds and then slowly goes down to 40v. After it goes below 40v, the inverter switches its display off. Not sure if this is to be expected (reading being averaged over time, or maybe capacitor discharging slowly), or if it could be an indicator of the cause.

Any ideas or suggestions will be welcome. Keep in mind that this is 100% offgrid and not connected to Eskom at all.
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coulomb
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Re: Axpert Error 51 repairs

Post by coulomb »

johnnyZA wrote: Wed, 12 Jan 2022, 20:43 Reversing the fans allowed it to keep working without issue for 14 months, and now the error is back.
Have you checked the page mentioning fault code 51 in the index (first post) of the repair topic? I've refreshed it a little.

User reports fix for fault code 51 (error 51: overload/surge). The link in the post and several posts following may be relevant.

In summary, it could be any one of these diodes: D24/26/15/14, or these 10μF M3216 (1206) ceramic capacitors: C31/74/30/29. You need to be handy with electronic repair for this level of board work. The fact that it's temperature sensitive suggests one of the capacitors; those high value ceramic capacitors are very sensitive to temperature, and even to the applied voltage.

NOTE: some of the posts seem to indicate that catastrophic failure (loud bang) is possible with this fault. Of course, your problem may be different, but it seems like a good clue.

Edit: also, 120 V PV voltage is high for a 145 V max PV model (MPPT upper limit is stated as 115 V), and low for a 450-500 V max PV model. You mentioned a VM model, I believe that all of those are the high PV voltage models. Your problem happens at about the hottest part of the day; hot panels have lower voltage. So you might need to add an extra panel, or rearrange the ones that you have. Though fault code 51 doesn't seem related to PV at all.
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Re: Axpert Error 51 repairs

Post by paulvk »

johnnyZA wrote: Mon, 26 Oct 2020, 18:19 Any ideas or suggestions will be welcome
You could try what I have done and add extra fans.
I used temperature controllers STC-100 to turn on extra fans when the heat sink gets above 46 deg c
I insulated the probe with heat shrink and glued it to the top of the heatsink.
I can see the temperature displayed on the controller you can use a 12v plug pack to run both the controller and the fans.
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Re: Axpert Error 51 repairs

Post by johnnyZA »

Thanks @coulomb that is excellent and very useful advice. Since working on electronics is far outside my skillset, I’ll maybe start with the basics. I’ll change the panel configuration to lower the voltage and find a way to keep it cooler.

Its sometimes too easy not to notice the obvious. Thanks for mentioning the mppt voltage range. I stared so many times at the 145voc max and completely ignored what was right in front of me :roll:

Thanks @paulvk, I think at this stage airflow inside the inverter is not really a huge issue. I added an external fan to its side that runs permanently. I think that is what helped it resolve the issue before. I’ll have to make a plan to cool the area around the inverter better. It might be that that spot is turning into a hotspot on those days with no real airflow possible there.
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Re: Axpert Error 51 repairs

Post by johnnyZA »

This is definitely temperature related in my case. Running with the cover off, I have no issues for weeks. With the cover on, it comes back in a few hours.

I found someone who can replace the 4 capacitors for me and am now trying to source 10 μF, 50 V ceramic capacitors. Getting them in surface mount is more difficult than expected, so will probably have to go for 10 μF, 100 V ceramic disc capacitors.

On the service manual for the VMII series uploaded by @coulomb on powerforum.co.za, I was quickly able to locate C31 and C74. But I can not find C30 and C29. Does anybody have a picture or a description of where on which board I might look for them?

Are there any other service manuals available for the VMII models or one for another model that will also be applicable to this one?
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coulomb
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Re: Axpert Error 51 repairs

Post by coulomb »

johnnyZA wrote: Tue, 15 Mar 2022, 16:50 Getting them in surface mount is more difficult than expected, so will probably have to go for 10 μF, 100 V ceramic disc capacitors.
Have you tried Mouser South Africa? Example: https://www.mouser.co.za/ProductDetail/ ... c%252Bk%3D
[ Edit: Oops! This is a 0.10 μF 50 V part; see next few posts for the 25 V 10 μF part. ]
But I can not find C30 and C29. Does anybody have a picture or a description of where on which board I might look for them?
Using the schematic PDF that I published (mostly Maxo's work), you can find that at least on the ancient board he traced, C29 and C30 connect to a winding on TX11 and TX10 respectively. I found them at the end of the middle heatsink with the IGBTs on them. Of course, your model may be different.

C29 C30 Axpert MKS 2013 sm.jpg
C29 C30 Axpert MKS 2013 sm.jpg (120.8 KiB) Viewed 9412 times
Are there any other service manuals available for the VMII models or one for another model that will also be applicable to this one?
What is "this one"? A VM II, III, or IV? That VM II manual is one of the best that there is, and it's the only one I know of for the VM II model.
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johnnyZA
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Re: Axpert Error 51 repairs

Post by johnnyZA »

Wow that was impressively quick. Thanks @coulomb

Yes, this is the VMII. The image you posted is perfect, thanks.
I did check the mouser website, but the shipping only to me costs the same as 120 capacitors. Looks like I did find them at rs components.
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Re: Axpert Error 51 repairs

Post by johnnyZA »

Should it be 0.1uF or 10uF? I notice that the product in your link is rated at 0.1uf, but in the post above you mention 10uF. Thats a big difference :shock:
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Re: Axpert Error 51 repairs

Post by coulomb »

johnnyZA wrote: Tue, 15 Mar 2022, 18:54 Should it be 0.1uF or 10uF? I notice that the product in your link is rated at 0.1uf, but in the post above you mention 10uF. Thats a big difference :shock:
Oops! They use a font with a tiny decimal point, and don't use a leading zero! Arrgh!

I'm fairly confident that the original capacitors should be 10 μF, but I was guessing about the voltage rating. When I thought I found an M3216 (1206 imperial) 50 V device, I thought why not be safe and use that. But looking at the circuit, it seems to me that it usually will see about 12 V, and a maximum of a little under 24 V, so a 25 V part should be OK. Sorry for the confusion!

So this part should be OK: https://www.mouser.co.za/ProductDetail/ ... 910uUDo%3D

Edit: but see my next post re X5R versus X7R.
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Patching PIP-4048/5048 inverter-chargers.
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johnnyZA
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Re: Axpert Error 51 repairs

Post by johnnyZA »

Thanks, that makes sense :D
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Re: Axpert Error 51 repairs

Post by coulomb »

coulomb wrote: Tue, 15 Mar 2022, 21:07 So this part should be OK: https://www.mouser.co.za/ProductDetail/ ... 910uUDo%3D
I note that the above is an X5R part; it is probably worth paying a fair bit more and getting the X7R part. X5R parts are rated for 85°C; X7R for 125°C. The X7R also have a slightly flatter K (relative permittivity) versus temperature characteristic, which can't hurt. Especially when temperature sensitivity is the issue here.

That also reduces the 120:1 shipping cost to actual capacitor cost ratio :D
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Patching PIP-4048/5048 inverter-chargers.
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Re: Axpert Error 51 repairs

Post by johnnyZA »

Thanks @coulomb that is very useful to know.
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Re: Axpert Error 51 repairs

Post by mariusvaida »

I run off-grid a VMIII 48V clone and this morning the inverter was off. I tried to start it and after the countdown F51 was displayed and after a few seconds F03. I use li-ion 14s70p and the bms displayed that the voltage was at 50,2V and about 72% remaining capacity, so the problem wasn't from the battery like stated in error F03. I disconnected the battery and run it only from solar, it started and it run for about an hour and then again shut down itself. This time i could not start it again, it showed the same error codes and power off. One strange thing was that it displayed over 600V from PV and 29A, even with the PV disconnected.

I opened up the inverter and i noticed 2 bulged capacitors (1000uF/16V and 470uF/25V), i replaced them and now it seems to run fine. I will monitor it closer in the next days.
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Re: Axpert repairs

Post by Badger »

Hi Guys.
Firstly I am new to this forum for postings but have been looking at it for a week or so.
So here is my story, I hope it helps someone else.
I had 4 Aexpert 5Kw inverters dumped on me by my brother that came from his and an associates installation, all with the same fault. The display was flashing and the inverter was cycling through its startup and then shutting down again in a one second cycle.
I have a fair amount of test equipment and experience in both electronics and RF equipment so I decided to try and fix them.
I tracked the fault down to an unstable 5V line on the main PCB.
Having a look at the 5V line with an oscilloscope showed large spikes on the line at the switching frequency of the power supply.
I then removed C79 and C95 and tested them with a capacitance meter, C95 which is a 100uF read as 9.5 pF (Open circuit) and C79 as 530uF about half its value.
I replaced all of the caps in this power supply section as a precaution because if two were this bad the rest were not far behind.
Reassembled the inverter and it powered up with no problems.
Did the same to the remaining 3 inverters with the same result.
So for less than R50.00 I now have 4 working inverters.
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Re: Axpert Error 51 repairs

Post by weber »

Awesome work, @mariusvaida and @Badger. Thanks so much for sharing.
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Re: Axpert repairs

Post by Kamil said »

Badger wrote: Sat, 21 Jan 2023, 00:48 I then removed C79 and C95 and tested them with a capacitance meter, C95 which is a 100uF read as 9.5 pF (Open circuit) and C79 as 530uF about half its value.
Hi @everyone
What is the reason for this?why inverter shows fault F51 ?
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