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Axpert MKS 5KVA Inverter - 48V


Johan Brits

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31 minutes ago, superdiy said:

The Axpert inverters cannot combine power sources; if the load requires more than the available PV at any point in time, the inverter switches the load to the grid (BYPASS) and use only the grid to supply the load until the available PV increases or the load drops. If the load is e.g. 2KW and the available PV is 1KW, the inverter will switch to BYPASS and draw 2KW from the grid and 0KW from PV.

Just to correct this, the Axpert can't combine grid with it's other two sources PV and Batt but it can combine PV and Batt
So in the 2KW load with 1KW PV Example, PV will supply 1KW and the Batts the other 1KW unless you put it in bypass and grid supplies all the load

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17 hours ago, superdiy said:

The INPUT connection is actually the GRID connection on these inverters. It is used to supply power to the inverter when the batteries needs to be charged by the grid or if the load is greater than what can be supplied by PV and / or batteries, depending on the configuration. It is also used as an output to the grid (feed in to grid) connection if the load requires less than the available PV and / or battery. The balance is fed to the grid via the INPUT connection, again depending on the configuration. 

The purpose of the OUTPUT connection on the inverter is to supply the LOAD.

Thank you (everybody) for the responses. 

Q1:  which setting needs to be set to enable/disable extra power to be put back on the GRID input connection?

Q2: Currently my GRID input to the inverter is via a lead with a general 3 point multiplug into a wall socket. 

       Thus i basically have a suicide plug scenario if you pull out of plug and the inverter is busy putting power back. 

Q3: Have some one measured current flow in that direction?

Q4: Does the inverter display show power flowing towards the GRID ?

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43 minutes ago, Fritz said:

Thank you (everybody) for the responses. 

Q1:  which setting needs to be set to enable/disable extra power to be put back on the GRID input connection?

Q2: Currently my GRID input to the inverter is via a lead with a general 3 point multiplug into a wall socket. 

       Thus i basically have a suicide plug scenario if you pull out of plug and the inverter is busy putting power back. 

Q3: Have some one measured current flow in that direction?

Q4: Does the inverter display show power flowing towards the GRID ?

A1: If you have one of these 5KVA Axpert inverters, it will not be able to push back to the grid. On the capable inverters, it would be inverter specific, normally something like "Feed to grid".

A2: Most inverters (except for certain BLUE ones :D) have built-in anti-islanding features which will immediately stop pushing back to the grid when the grid fails, so basically if your inverter was capable of pushing back to the grid, the moment you unplug your plug from the wall socket (in your case) the inverter will stop pushing to the grid and you won't get a shock if you touch the 3 prong plug. Unlike the famous rooky generator connections.

A3: It depends on the capabilities of the inverter, e.g. my 3KW infini can push back up to 3KW which would be about 13A @ 230V.

A4: Again it depends on the inverter, but the infinis do and I think the Imeons do as well. I am not familiar with other brands.

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2 hours ago, Fritz said:

Q1:  which setting needs to be set to enable/disable extra power to be put back on the GRID input connection?

Q2: Currently my GRID input to the inverter is via a lead with a general 3 point multiplug into a wall socket. 

       Thus i basically have a suicide plug scenario if you pull out of plug and the inverter is busy putting power back. 

Q3: Have some one measured current flow in that direction?

Q4: Does the inverter display show power flowing towards the GRID ?

Okay, so others here have already covered the basics, that the Axpert inverter cannot in fact do this, so my answer is only in respect to those inverters that CAN in fact do this. I know the Victron best so my answers might have a slightly blue tint to them.

1. The setting you need to enable will depend on the inverter mode. On the Victrons you have to install extra software (called assistants) into the inverter programming to make it work. On the infini I believe there is a checkbox you tick somewhere in the configuration tool.

2. Suicide plug. This is what anti-islanding is all about. There is a requirement that embedded generators should detect the outage and disconnect themselves to prevent feeding back power when the grid is down. There are standards for that (VDE-AR-N 4105 is the German one, CEI 0-21in Italy, NRS 097-2-1 in South Africa). Before you connect your inverter to the grid, you need a certificate proving that it supports that standard. If it supports that standard, it will avoid the suicide-plug scenario. There are edge cases (so called Non Detection Zones, NDZ) where the inverter might not detect it, but this is really very rare. It relies on the outage being so subtle that no frequency shift, power vector shift, or voltage drop is detected, which is rather unlikely.

3. Current flow is a misnomer. With AC current flows backwards and forwards all the time, it changes direction 100 times a second :-) What you want to look at is the so called "power vector". Not sure how strong your math is or if you've seen the first Despicable Me movie, but a vector is something with both magnitude and direction. We're interested in the direction of course. The power is a product of the current and voltage. Things get a bit technical here, because the current and voltage is not necessarily exactly in phase (the so called power factor), but to put that simply: If your voltage and current is in phase (the product of the two, on average, is positive) you're drawing power, and if they are out of phase (the product of the two, on average is negative) then you are pushing power back. You cannot determine the direction of flow without measuring all three of voltage, current and phase angle. :-)

4. Inverters that support pushing back will show a negative number (usually) when they push back. Of course someone will remind me that the Victron has no LCD and therefore doesn't display anything other than some confusing blinken lights... :-P... but in theory, when you have the CCGX installed, it shows it :-)

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Of those who have had an MPP SOLAR product develop a fault, what was your experience with them? 

I have found them to be evasive and uncooperative. 

Back in January I noticed a little smoke, so I filled in one of their forms and supplied the extra information. No response. The inverter kept working so I didn't bother chasing it up.

A few weeks ago the 230v stopped outputting so I filled in a form again. 3 days passed. Their website says 24-48hrs response. So I told them if they were going to ignore my request for service once again I was going to take to the forums to warn people about the lack of warranty. 

I got an immediate response, was sent some pdfs for disassembly and diagnostics. I spent several hours doing that and emailed them the results. 6 days since, no response and I'm really pissed off!

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1 minute ago, Northland said:

Of those who have had an MPP SOLAR product develop a fault, what was your experience with them? 

I have found them to be evasive and uncooperative. 

Back in January I noticed a little smoke, so I filled in one of their forms and supplied the extra information. No response. The inverter kept working so I didn't bother chasing it up.

A few weeks ago the 230v stopped outputting so I filled in a form again. 3 days passed. Their website says 24-48hrs response. So I told them if they were going to ignore my request for service once again I was going to take to the forums to warn people about the lack of warranty. 

I got an immediate response, was sent some pdfs for disassembly and diagnostics. I spent several hours doing that and emailed them the results. 6 days since, no response and I'm really pissed off!

So, what exactly did you get through the diagnosis?

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I've read that part of their service manual and I had my misgivings about that. It's probably a good first test, but you don't really know what is wrong with something unless you actually take it out of the circuit and test it. So take Q6 for example, with the gate to drain short. Well, that strikes me as obviously wrong, but it is rare (in my limited experience) to find a short on the gate, and far more likely to have a short source to drain.

Also, the gate on a FET is isolated from the source and drain (it's behaves like a small capacitor, when the cap is fully charged the FET switches on) and the only real way to make it short to one of the others is to put too high a voltage on the gate, which is rare given that the voltages you need to fully switch a FET on is already so high that designers usually have a problem with the reverse: Not switching it on fast and/or hard enough.

So I half suspect that Q6 is fine but whatever is driving it is blown. A few months ago I disassembled a WRND charge controller and posted the results here, and I had the same result there: First I thought gate was shorted to drain... when I took it out of the circuit, I found the FET to be fine, but the driver was ISM (Afrikaans abbreviation for "very far gone" :-) ).

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  • 2 weeks later...
On 2016/09/02 at 9:24 AM, Chris Hobson said:

Voltronic have caused some confusion as they have recently released an Infinisolar Axpert V series which can grid-tie. Jaco de Jongh has one, but traditionally Infinis can gridtie and Axperts cannot.

Anybody looking for the MECER SOLAR HYBRID or AXPERT INVERTER manuals or service manuals can download it for free at  www.2k11.co.za/SOL-I-AX-5M-manual and the service manual at www.2k11.co.za/SOL-I-AX-5M-service-manual.

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1 hour ago, Simplesimon said:

Anybody looking for the MECER SOLAR HYBRID or AXPERT INVERTER manuals or service manuals can download it for free at  www.2k11.co.za/SOL-I-AX-5M-manual and the service manual at www.2k11.co.za/SOL-I-AX-5M-service-manual.

Thanx for advertising your website, but those manuals are freely available on the Voltronic website as well as this website. 

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  • 2 weeks later...

hi Guys

Please forgive me if my question was answered before on this thread. 13 pages was just getting a bit to long for me...

The axpert 5kva has a PV max power input of 3000W.

Max PV current = 60A

Max PV voltage = 145V

Example: if one runs PV input @  50A x 100V  = 5000W what wil happen , unit max = 3000W

Can this be done safely and do someone have proof( photo) of PV input on the inverter window?

 

 

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15 minutes ago, Fritz said:

Example: if one runs PV input @  50A x 100V  = 5000W what wil happen , unit max = 3000W

These things are rated by the battery side. So battery voltage times max current. When the batteries are at absorb (lets say 60V to make the math easier, I know the Axpert can't take them that high), then 3000/60 = 50 amps. So it can do max 50 amps on the output, but because of the down-conversion that happens in the buck converter in the MPPT, You will have (60/100)*50 = 30 amps on the PV side.

If you oversize the array so that it is actually capable of 50 amps, a good MPPT will limit the output to the max, so it will use only 60% of the available current to make the max on the battery side.

There is some anecdotal evidence that running these chinese MPPTs full tilt for extended periods might not be conducive to a long life, but I simply don't know. I'm sure someone here will tell us how their uncle smoked for many years and only died at... oh wait, wrong debate :-P

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4 minutes ago, plonkster said:

There is some anecdotal evidence that running these chinese MPPTs full tilt for extended periods might not be conducive to a long life, but I simply don't know. I'm sure someone here will tell us how their uncle smoked for many years and only died at... oh wait, wrong debate :-P

Solarmahn (who works in Papua New Guinea) on the AEVA regularly oversizes the PV array on Axperts by about 40%.

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1 hour ago, Chris Hobson said:

Solarmahn (who works in Papua New Guinea) on the AEVA regularly oversizes the PV array on Axperts by about 40%.

I oversize by 10% (12x 260W panels), although we've done couple with 12x 3000W panels (20%) without any problems so far. Since current is drawn, just about any device will only use what it can, so the oversize PV array helps a bit with cloudy days / winter / etc. 

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Just now, SilverNodashi said:

current is drawn

Yup, the MPPT will only draw what it can handle. My contention is that sometimes the designers of such systems over-estimate what it can handle, and because the majority of people might never use the capacity such mistakes only surface when you oversize. It's just something I heard, it seems from the reports above that the Axperts are perfectly fine with extended running at maximum capacity.

As an aside, it's actually interesting how some MPPTs handle this situation (where it has to limit current). The obvious answer is to run the PV at a voltage level where it cannot sustain high currents, and there's two ways to do that: Either run it at a voltage lower than Vmp... or run it at a voltage between Vmp and Voc. As far as I know, MPPTs use the second method.

That makes intuitive sense to me. You have to run the PV array at a voltage equal or higher than the float voltage of your battery bank, and at that voltage it might simply make too much current. If you run it above Vmp up to Voc (when the current becomes zero) you have none of those problems. It does mean though that with oversized arrays, you had better be sure you have space at the top. On a cold bright morning with high open-circuit voltages and a full battery bank... you never know :-)

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2 minutes ago, plonkster said:

Yup, the MPPT will only draw what it can handle. My contention is that sometimes the designers of such systems over-estimate what it can handle, and because the majority of people might never use the capacity such mistakes only surface when you oversize. It's just something I heard, it seems from the reports above that the Axperts are perfectly fine with extended running at maximum capacity.

As an aside, it's actually interesting how some MPPTs handle this situation (where it has to limit current). The obvious answer is to run the PV at a voltage level where it cannot sustain high currents, and there's two ways to do that: Either run it at a voltage lower than Vmp... or run it at a voltage between Vmp and Voc. As far as I know, MPPTs use the second method.

That makes intuitive sense to me. You have to run the PV array at a voltage equal or higher than the float voltage of your battery bank, and at that voltage it might simply make too much current. If you run it above Vmp up to Voc (when the current becomes zero) you have none of those problems. It does mean though that with oversized arrays, you had better be sure you have space at the top. On a cold bright morning with high open-circuit voltages and a full battery bank... you never know :-)

Well, in the Axper's case (this is an Axpert thread, after all ;) ) If you run say 12x 250W Renesola panels (max PV array) then you would ideally be running at about 112.2V (VOC) & 33.24A (Imp). 260W panels would push it to 112.8V & 34.12A.

300W Renesola panels would push it to 134.4V & 32.8A @ 3600W. 315W would give 135V and 33.52A. 

So you're safely below the Inverters Voc and Amp limit, but it could cause problems with cloud edge effect, where some people have reported 120%+ energy delivery on their systems, albeit for short periods of time. Just use the right size fuses, i.e. at least 20% higher than your expected current draw. I've seen 10A fuses blow too often so I started using 12A fuses a couple years ago. Less nuisance blown fuses. 

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I can understand that you would over size the PV array on papier to compensate for weather etc...

but i still wonders what happens in practise.

Let say i oversized my array and it can produce 3500W , 35A x 100V (500w more than the datasheet) and my load = 4000W

Will the MPPT draw 3000W and be happy to supply that + 1000W from batt to get to 4000W

or

Will the MPPT draw 3500W + 500W from batt to get to 4000W

or

will the MPPT blow because it exceeded the max power rating of 3000W

?

 

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4 minutes ago, Fritz said:

I can understand that you would over size the PV array on papier to compensate for weather etc...

but i still wonders what happens in practise.

Let say i oversized my array and it can produce 3500W , 35A x 100V (500w more than the datasheet) and my load = 4000W

Will the MPPT draw 3000W and be happy to supply that + 1000W from batt to get to 4000W

or

Will the MPPT draw 3500W + 500W from batt to get to 4000W

or

will the MPPT blow because it exceeded the max power rating of 3000W

?

 

In practice, my own house runs on 265W panels. No problem ;)

Most of our clients either run 255W or 260W solar panels - depending on what we can get and their budget. Some clients run 300W panels. The MPPT will draw what it can, within limit. i.e. if there's 3KW PV array available, you'll probably get about 2600W (+-). A 3500W PV could probably produce 3000W. You very seldom get 100% PV output. With cloud edge effect you might get a bit more, for a couple minutes, or an hour, but it's very seldom and doesn't last very long. 

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12 minutes ago, Fritz said:

Will the MPPT draw 3000W and be happy to supply that + 1000W from batt to get to 4000W

^^^ That one. But lets get rid of the power figures and talk current.

It makes no sense to talk in terms of power because the limits on the MPPT is not in power but in ampere, so the amount of power depends on the voltage that you are working at.

If the controller can do max 60A and your batteries are at 48V, then it can do 2880W. If the batteries are at 57.6V (Absorb) it can do 3450W.

The same goes for the inverter side. At the lower voltage it needs 83 amps to make 4000W. At the higher voltage it takes 70 amps to make the same power. So on the lower voltage, 23A will come from the battery, and at the higher voltage, 10 amps will come from the battery.

The difference will always come from the battery because in the Axpert, the MPPT is connected directly to the DC bus, the DC bus is connected to the battery, and the inverter is connected to that same DC bus. It's all interconnected. It is no different to what us non-Axpert people do with our external charge controllers. We just have extra cables around :-)

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Just now, SilverNodashi said:

And extra cash ;) /hides

No. We spent it. On the extra cables and charge controllers :-P

I still prefer my charge controller to go directly to the battery with a separate (thicker) cable from the battery to the inverter, and a large fuse between the inverter and the battery. In my mind's eye I imagine what happens when you have the inverter and the MPPT hard-wired to each other on a bus, with a fuse between that bus and the battery, and then the fuse goes while under full load. So now the inverter and the MPPT are duking it out and it's clear things won't go well and in the best scenario a shutdown will follow. The MPPT is going to back off as the load changes... but will it do so quickly enough not to cause a severe overvoltage situation and blow stuff up? I would like to think that the designers thought of that... really, I would :-)

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