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Axpert with Victron MPPT - does it make sense and how would it work?


wolfandy

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Hi all

as mentioned in my other thread, my installer is recommending that I add a Victron MPPT to my Axpert/Pylontech and 3x 3S 315W panel setup (and not use the Axpert MPPT). His arguments are that with the 250V Victron (and 2x 5S configuration) I would have lower system losses, faster tracking, and earlier start-up / later shutdown - and hence overall higher system yield.

I've found an older comparison of the Axpert MPPT and a Victron MPPT here in the forum and their performance on good days seems to be identical, but there were discussions around performance on cloudier days. Does anyone have any more recent experience by chance?

What would your overall advice be - would this make sense?

And how would it actually all work together? I understand that you would wire the Victron MPPT on a common busbar with the Pyontech and Axpert battery connection. But how would it all communicate? I've seen that ICC now has an option for Victron MPPT but do not yet know if it is 2-way communication or can only read data from the Victron. Would I need a Venus device to get the Victron MPPT and the Pylontechs to work together ? If yes, how would that then work together with ICC?

Thanks for your advice 😀

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Right... a lot to say here 🙂

First on the how it would work. Since the Axpert doesn't do any state of charge measurement of its own and only looks at voltage, it really doesn't matter too much if you use an external MPPT to get the energy into the battery. I'm not sure how it would interact with the various "programs" of the inverter, I mean there are thing like SBU (solar before utility) where I assume the presence of solar power affects how it works, so I assume some changes will be required, but overall I suspect it will just work.

1 hour ago, wolfandy said:

I've found an older comparison of the Axpert MPPT and a Victron MPPT here in the forum and their performance on good days seems to be identical, but there were discussions around performance on cloudier days. Does anyone have any more recent experience by chance?

There are some things to know about that test.

The first is that the values returned by the hardware itself was used, so it did not account for calibration differences. The slight bit by which either charger outperformed the other was too small to crown either one a winner. Ideally one should have used a third-party measurement, eg a separate battery monitor, for both tests.

The second is that it didn't test the speed of tracking, ie how fast the tracker finds a new maximum after conditions change. The Victron charger tracks faster, that is true, but in the South African context I'm not sure if that will provide significant additional generation, given that our cloud scenario is usually somewhat all or nothing 🙂

The third is that it benchmarked one of the less expensive Victron MPPTs. There is something called an overcurrent event, that is when conditions change suddenly and the current value rises sharply and exceeds the limit of the charger before the control loop can pull it back. The cheaper controllers (which also includes the Axpert) shuts down and restarts from zero. The higher-end Victrons have a hardware current clamp and avoids this restart. So already this comparison is not helpful to the chargers you're considering.

Fourth, I think what your installer is aiming for is the lower cable losses. The Axpert has a fairly narrow power band between 80V and 135V. Even though it is rated to 145V, it starts to derate. This means that for an Axpert the optimum setup is 3 x 60-cell modules in series. 4-wide the open circuit voltage becomes a tad too high, and with 72-cell modules you have that problem even earlier (max 2-series, at 3-series you're pushing 150V on a cold morning). Since most of the affordable and larger modules are now 300W and above, even the 150V chargers from Victron (no derating, but they also shut down above 145V) are somewhat limiting. This means thicker cables, more of them, and because of the narrow voltage band, it does mean a slightly shorter solar day. So I think this is the big item he is aiming for: With a 250V charger you'll get a bit more juice out of it.

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1 hour ago, wolfandy said:

But how would it all communicate? I've seen that ICC now has an option for Victron MPPT but do not yet know if it is 2-way communication or can only read data from the Victron. Would I need a Venus device to get the Victron MPPT and the Pylontechs to work together ? If yes, how would that then work together with ICC?

Neglected to answer this. For the most part you don't have to communicate with the MPPT. You do lose one feature a Victron system provides (the battery can request a lower charge current and the MPPT will limit itself), but again, since the Axpert had none of that to start with, you're not losing anything. The production values of the MPPT is communicated using plain text on a TTL-serial link, using the VE.Direct text protocol... the same protocol used by the BMV. This is probably what ICC does anyway.

There is a lot of other features hidden behind the VE.Direct hex protocol... but that's for more advanced stuff. Nothing you will really miss.

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Thanks a lot for the detailed feedback, plonkster 😀

Quote

The third is that it benchmarked one of the less expensive Victron MPPTs. There is something called an overcurrent event, that is when conditions change suddenly and the current value rises sharply and exceeds the limit of the charger before the control loop can pull it back. The cheaper controllers (which also includes the Axpert) shuts down and restarts from zero. The higher-end Victrons have a hardware current clamp and avoids this restart. So already this comparison is not helpful to the chargers you're considering.

I am looking at the Smartsolar 250/85 - am I correct to assume that this falls into the higher-end category and has a hardware current clamp?

Quote

First on the how it would work. Since the Axpert doesn't do any state of charge measurement of its own and only looks at voltage, it really doesn't matter too much if you use an external MPPT to get the energy into the battery. I'm not sure how it would interact with the various "programs" of the inverter, I mean there are thing like SBU (solar before utility) where I assume the presence of solar power affects how it works, so I assume some changes will be required, but overall I suspect it will just work

On the Axpert side I believe things would be straight forward. SBU actually stands for 'Solar -> Battery -> Utility' and hence the Axpert should behave the same regardless of whether it receives PV directly connected to the internal MPPT or through an external MPPT via the battery. Once solar is 0 (which it then always will be) and the battery SOC has reached the point set in ICC, it will switch to Eskom. And once the battery SOC has increased to the point set in ICC, it will switch back to SBU.

Quote

For the most part you don't have to communicate with the MPPT. You do lose one feature a Victron system provides (the battery can request a lower charge current and the MPPT will limit itself), but again, since the Axpert had none of that to start with, you're not losing anything.

Maybe my understanding is wrong and I am over-complicating things: Do the MPPT and the Pylon BMS need any kind of direct communication? Or does the MPPT change between bulk, float, etc purely based on the voltage that it reads? In all the Victron schematics that I found both the Pylons and the MPPT are always connected to a Venus device. 

Edited by wolfandy
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4 minutes ago, wolfandy said:

I am looking at the Smartsolar 250/85 - am I correct to assume that this falls into the higher-end category and has a hardware current clamp?

Correct. All the 250V models uses the newer platform, it also has a different CPU and some other things you will not know by just looking at it 🙂

 

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29 minutes ago, PJJ said:

Just out of interest, do the newer 150/100 SmartSolar units also have the hardware current clamp?

I think it does, though I am no 100% sure. The BlueSolar models don't have it, but smaller SmartSolars (The 100V models, eg the 100/50, and anything smaller than and including the 150/35) also don't have it. The 150/45, 150/65, and above has it.

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  • 5 months later...

Hi WolfAndy,

did you install the Victron MPPT and if yes, how is it going? My Kodak blew up after fitting panels and while I wait for it to return, if ever, I’ve been looking at other options, to keep my panels working, but would then still not have inverter.

If the supplier returns my inverter fixed, I would configure it the same as you were planning on doing, and when the inverter blows up again in the future ( hopefully it wouldn’t), I could move over to a Victron Multiplus II as I would already have the MPPT.

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I'll add my +1 here, I had it working with my Axpert 3kVa with a Victron MPPT, just no Raspberry Pi - thanks to advice from @wolfandy over on one of my threads. Setting the Axpert to SBU worked like a charm, my inverter seemed happier without having to worry about MPPT. It also allows for greater expandablilty in the future.

Ultimately I opted for the Multiplus II, no looking back.

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  • 3 weeks later...
On 2020/06/27 at 4:41 PM, wolfandy said:

Yup. Installed a Victron 250/100 MPPT with 12x 380W panels and a VE.Direct cable to my ICC Raspberry Pi. Everything works like a charm and I am very happy with my setup 🙂

Hi WolfAndy, I have 12 x 370W and have a 250/100 on its way. 😊 How did you configure the panels? 3 strings of 4? Did you use MC4 "Y" connections to "parallel" them?

Thanks in advance!

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2 hours ago, Mark Y-M said:

I have 12 x 370W and have a 250/100 on its way. 😊

Very nice 😬

2 hours ago, Mark Y-M said:

How did you configure the panels? 3 strings of 4?

Yes. 3 strings of 4 panels in series. But I would recommend confirming with the Victron MPPT calculator tool that that configuration also works for your panel specs and temperature environment

2 hours ago, Mark Y-M said:

Did you use MC4 "Y" connections to "parallel" them?

I have to admit that I have no idea. My installer wired everything up for me 😝

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  • 2 weeks later...

Hi @wolfandy, I am looking at doing this same setup on my Infini,  but will still keep some PV on the Infini side, and was wondering how ICC would display the MPPT values.

I suppose I will see a value for each MPPT on the dashboard with their amps and voltages and the combined PV total will be displayed.

 

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4 hours ago, francois said:

I am looking at doing this same setup on my Infini,  but will still keep some PV on the Infini side, and was wondering how ICC would display the MPPT values.

I suppose I will see a value for each MPPT on the dashboard with their amps and voltages and the combined PV total will be displayed.

I have to admit that I have no idea. I get a separate tab for the Victron MPPT (see below) and the PV Watts are reported on Dashboard 2 (but not voltage or amps)

MPPT.thumb.JPG.1ff3f4faba8ba83d60d1184811a45308.JPG

Maybe reach out to Manie and ask him for details?

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6 hours ago, wolfandy said:

I have to admit that I have no idea. I get a separate tab for the Victron MPPT (see below) and the PV Watts are reported on Dashboard 2 (but not voltage or amps)

MPPT.thumb.JPG.1ff3f4faba8ba83d60d1184811a45308.JPG

Maybe reach out to Manie and ask him for details?

Perfect thank you. Nice to see everything on a seperate tab with detailed information.

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  • 4 weeks later...
On 2020/06/27 at 4:41 PM, wolfandy said:

Yup. Installed a Victron 250/100 MPPT with 12x 380W panels and a VE.Direct cable to my ICC Raspberry Pi. Everything works like a charm and I am very happy with my setup 🙂

Hi @wolfandy, how does your ICC PV graph look during the day? Is it smooth or does it have these little dropouts throughout the day?

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  • 5 months later...
On 2020/06/27 at 4:41 PM, wolfandy said:

Yup. Installed a Victron 250/100 MPPT with 12x 380W panels and a VE.Direct cable to my ICC Raspberry Pi. Everything works like a charm and I am very happy with my setup 🙂

Hi @wolfandy can I ask you a question. I have 2 Axperts in parallel, with a Victron 150/70 MPPT. When I put the axperts in SBU they immediately go to bypass, while the battery is full (55V) and above the [20] setting which is 50V. Would you mind sharing all your settings so that I can try them out? Many thanks in advance

Edited by BasZ
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36 minutes ago, BasZ said:

Would you mind sharing all your settings so that I can try them out?

Hi @BasZ, here are my settings

ICC.thumb.JPG.f6b847cd53b1b9289c254b6e8ee3d834.JPG

As I am using ICC, I have all my Axpert settings in a way that they do not interfere with ICC

Do you maybe want to post your settings - and I can see if I spot anything?

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1 minute ago, wolfandy said:

Hi @BasZ, here are my settings

ICC.thumb.JPG.f6b847cd53b1b9289c254b6e8ee3d834.JPG

As I am using ICC, I have all my Axpert settings in a way that they do not interfere with ICC

Do you maybe want to post your settings - and I can see if I spot anything?

Sure, although I do the settings on the axperts themselves. 
 

1: SBU

2: APL

3: 230

4: 50 Hz

5: BLU

6: Bye

7: LrE

8:trE

10: OSO

11: 60A

13: 30A

14: USE (I have blue nova)

17: 56.1V

18: 55.9V

19: 48.0V

20: 50.0V

21: 52.0V

22: Ptd

23: LOF

24: bOF

25: AOF

27: FON

i have 3.96kWp on the roof, and 2 axperts in parallel. Battery is 8kW. I’m not an expert ...

the system is connected to Eskom (grid tied) but does not deliver back into the grid

hope you can help  

 

 

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1 hour ago, BasZ said:

hope you can help  

You seem to have a slightly different model number to mine - so our program numbers do not line up (and some settings I do not recognize, e.g. 22)

From what I understand, you use the following settings - correct?

Bulk: 56.1V

Float: 55.9V

Low DC Cutoff: 48.0V

Back to Grid: 50.0V

Back to Battery: 52.0V

That would look ok

Is your Axpert showing on the display 55V for the battery when going into bypass? Do you have any major loads connected at that point that could cause a dip in the battery voltage? 

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On 2021/02/05 at 6:49 PM, wolfandy said:

You seem to have a slightly different model number to mine - so our program numbers do not line up (and some settings I do not recognize, e.g. 22)

From what I understand, you use the following settings - correct?

Bulk: 56.1V

Float: 55.9V

Low DC Cutoff: 48.0V

Back to Grid: 50.0V

Back to Battery: 52.0V

That would look ok

Is your Axpert showing on the display 55V for the battery when going into bypass? Do you have any major loads connected at that point that could cause a dip in the battery voltage? 

Hi @Wolfandy, sorry for the delay in getting back. Yes, the axpert is showing voltages >52V (up to 55V) when going into bypass.

In the meantime I have been doing some experimenting with the Axpert settings. I had more luck with setting [5] on LBU instead of BLU (I did not change anything else). The battery supplies the load when it can and bypass is only coming on sporadically. I still have the following questions for any Axpert guru's out there:

- I had thought that with all my settings above and [5] on LBU that Eskom would keep my battery at 50V, but am seeing that it is drawn down all the way to 48V during the night. Why would this be? I am assuming this to be harmful for the battery?

- While it is less I still see the bypass kick in during the day when solar is charging the battery and Vbatt > 52V. Why could this be (according to the manual it should not be happening)? Loads are less than 1000W, which is much lower than the capacity of the battery and inverters, so Eskom should not be needed at all?

Any input very much appreciated

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