Hey Folks!

I've recently put in a Axpert VM3 5K system and am currently experimenting with it before getting it integrated into any DB boards.

Currently I have 8x 310W panels in series giving the inverter 300v at around 7 amps for around ~2000W of power

I also have a 2.4kwh 48v lithium battery for load shedding.

I have a small current meter on the input side of the inverter, and can see the current out of the inverter through the 'powerwatch' app on my phone through bluetooth.

With the inverter in SUB/ Solar-Util-Bat mode, all of the required power gets drawn from the eskom grid, and PV power is not used at all, my current meter sees 300w coming into the inverter from eskom, and the inverter tells me there is 300w coming out to power my computer which I have plugged in as a test load.

I've tested this with small 50w load, and running a 1000w aircon, it only draws power from the grid in SUB and is not supplementing with solar energy.

 

Those familiar with the VM3 will know there's a display icon which shows BYPASS ------>

The inverter is permanently on bypass unless I obviously turn off the eskom power, or change the inverter mode to SBU Solar-Bat-util, which then drains the battery which I want to keep full for load shedding. On this mode there is a "back to grid" voltage, but because I have a lithium battery, the settings on the VM3 does not let me set the back to grid voltage high enough to not drain the battery by a large amount.

 

Without Eskom available, I can then see the inverter start to draw current from the panels, and it draws exactly the right amount of power from the panels to power the load, I've even managed to run my 1000w aircon just from the panels.

 

Everywhere I look, I see that the VM3 has a "grid assist" function where it can mix PV & Eskom through a AC/DC/AC chain, but I can't figure out how to get this to work, and the solar panels are not being used during the day unless I remember to manually switch off & on the eskom power to the inverter

 

I'm wondering if it's a firmware thing?

According to the phone app at least, my current firmware version is 00041.15 for "Main CPU Version"

 

Anyone got any ideas? Have I missed a really obvious setting?

 

 

18 minutes ago, faux_grey said:

Have I missed a really obvious setting?

What is setting 16, charger source priority? 

17 minutes ago, Coulomb said:

What is setting 16, charger source priority? 

I have it currently set to "Solar First"

But I see no difference in operation when switching between:

"solar first"

"Utility & Solar"

"Only Solar"

OK, which of the following 5 modes is the inverter operating in?

Edit: it seems that the VM III, unlike at least the King, will show "BYPASS" in any line mode. So only in battery mode, standby mode, or fault mode will it not show "BYPASS".

Edited December 4, 20214 yr by Coulomb

@CoulombIt's in mode 3

But to re-iterate, using the watt-meter on the mains input shows it drawing full load from the mains to feed what is behind the inverter.

the app shows 0 watts drawn from panels in this mode which is a little sus.

On 2021/12/06 at 1:35 AM, faux_grey said:

the app shows 0 watts drawn from panels in this mode which is a little sus.

Certainly.

On 2021/12/04 at 7:30 PM, faux_grey said:

I'm wondering if it's a firmware thing?

According to the phone app at least, my current firmware version is 00041.15 for "Main CPU Version"

It seems unlikely to me, but it could be. 41.17 is available here (the Czech site). It might be worth updating to. I just had a look at my disassembly of it, and it's very primitive; I've not had reason to work on it much. So sadly I can't tell you what changes there are from earlier versions.

The part of the firmware that decides how much of each power source to use is complex, and not it's not an area that I've analysed for the high voltage models.

@Coulomb I havent got round to updating the inverter yet (need to find my serial cable)

But I have noticed, when in USB Utility-solar-bat, the inverter seems to draw all the required load from the panels, and only around 50w from mains.

When doing this, it reports 0w being drawn from the panels, and my battery reports 0w being drawn from it, yet I have a 600w load running and only 50w drawn from main supply.

My only explanation is there is a firmware issue causing USB to act like SUB and vice-versa, while also preventing correct measurements from the MPPT.

In my experience sub does not work on the axpert vm, axpert king, axpert max. It should mix the power in sub but it doesn’t it draws all the power from grid. The best setting that I have found is setting #1 SBU and then make sure setting #12 #13 is set correct then set #16 to CSO if you are worried about load shedding and OSO if you want to save on your bill. The only thing with this setting is that you sould  make sure your pannels is big enough to power your load and charge your battery.

Sub mode on my mk2 runs well, if there's pv voltage it switches to sol and batt, once there's no sol pv voltage (under min threshold) it reverts to grid, batt is only used until sol can carry the load and the energy used is then replaced. I do use icm though but can send a screenshot of the settings it uses if that helps

I don't use sub a lot though, and spend most of my time on sbu. You may pick up an issue in poor sol pv conditions where the batt may be used more than intended.

left it on sub for now, so tomorrow I can give actual stats so you know what you can expect, doing this because I doubt sub is going to give you the results you're expecting, maybe in winter with its shorter days.

now I don't get useful power at the outer times, trickles in around 7am, carries the load around 8-8:30, dies off around 4-4:30. 

You may also want to try an app replacement, my feeling as to the actual source of your issues, there's a decent free version for windows. 

http://www.multisibcontrol.net/

give it a try, last I used it, it occasionally froze on comms, maybe its been fixed, I wanted my laptop back, so moved to a linux embedded solution. 

I looked at its code  to maybe shift it over to .net core, and run it on linux, but wasnt worth the time and effort.

Here is the sub output, as you can see grid kicks in late and ends early, and the solar shown is during cloudy weather.

Edited December 22, 20214 yr by Nitrious

Heres your solution, note the time control aspect for different modes. puts you in control in all aspects. it really needs a pv output setting, in case of good/poor weather, switch to solar/grid. just run sbu from 8am-4pm, grid the rest of the time.

axperts, being in the economy segment of the inverter market, offer a lot of value but need intelligence added, as well as protection from itself.

most inverters in the upper end of the spectrum can deal with oversized arrays with ease as an example (most of the time), while the axpert is at risk of simply "letting go", so I'm building a mppt protection device for mine on max voltage, max current , max power to ensures it doesnt  just give it up in the event I'm pulling more than I should.

 

Edited December 21, 20214 yr by Nitrious