networking mppt controllers

Tundra57 · July 2020

I have factory solar and external additional solar panels. Both systems have a seperate victron mppt controller. Outputs are wired in parallel to the battery. I noticed that only one controller will take the load. They do not share. Apparently this has been an issue as far back as 2019. Vicron has been working on a synch method which supposedly is now implemented early 2020. However to use the feature you have to set up a network. For this you need a victron device such as the victron blutooth power monitor many of you are currently using. I did not realise this until I read blogs on the Vicron forum.

I now am ordering the monitor to see if this synch software actually works.

Without, when the controllers see float less than 1Amp load they will go to sleep. But if the battery gets discharged, only one of them will wake up. Apparently it is random which one does. In my case i noticed it as my external mppt took up load but the factory unit showed 0Amps. If i disconnect my external, the factory mppt comes on line.

Has anyone with multiple mppt's set up a network with the power monitor and saw full sharing of the controllers?⁸

ChanW · July 2020

We don't have two controllers, but this might help to explain the behavior of ours that I saw when we were on the road in March. We do have the Battery Monitor so I was able to closely watch what the system was up to while we drive.

Our solar is on our truck's rack, and it remains connected to the Tab while we drive. I figured we'd have solar charging boosting the alternator output, and maybe even enough to run the 3-way.

However, it didn't work that way. The Victron Controller would cut the solar off after a time (I couldn't see the pattern), and we were left with just the alternator charge. I finally 'solved' it by disconnecting the alternator charge line to the Tab, and had the solar do all the charging (all day driving in sunny weather).

I'd like to see them address this situation also, as it seems that two charging systems should be able to co-exist on the battery bank. A case for it would be in marine setups, where I'd think this would be common, charging from the vessel's power unit as well as the solar. Though I can see how, in this case, it might be difficult or impossible, since the Victron system has no control over the alternator charge output.

MarkAl · July 2020

Yep, I went with the Victron Smartshunt to do the battery monitoring, then Victron's MPPT controllers arbitrate over the BT (or physical) network to decide which device has the most energy available and coordinates the outputs to maximally charge the battery. Though I am waiting for more field data to decide what brand and size array to buy. It will have a unique Victron controller installed in the trailer for this reason.

Tundra57 · July 2020

I did not read in detail if the latest software upgrade fixes the issue by synching the mppt's.

I think ill read some more to see how the software fix works. I hope to install the battery monitor next weekend.

MarkAl · July 2020

You're ahead of me on the second controller / array - I've started researching panel vendors probably be a few weeks before I order. Glad you're paving the way

I have a friend who lives mostly off grid and he claims even with 100% extra capacity on an optimized collector in the winter, he still sometimes sips from the grid. So I'll probably have backup of a portable for Spring & Summer use and small generator for Fall & Winter. This year is our practice year, next year we retire and really head out.

plicato · July 2020

According to Will Prowse (https://www.mobile-solarpower.com/), my go-to source of anything solar power related, it is a common misperception that charge controllers “fight” each other when connected to a single battery.

You can connect any number of controllers, even of different types, i.e. PWM or MPPT, to a battery and they will work just fine. Here is Will’s explanation:
https://www.youtube.com/watch?v=rSj6-JSxoD4

He also explains the function of the battery-to-battery communication that some battery systems offer. The purpose is to synchronize the equalization of flooded cell batteries every 28 days. It has nothing to do with coordinating the controllers so they won’t “fight” each other.

I hope this makes sense and helps.

Paul

Verna · July 2020

I have two Zamp 100 watt flexible solar panels on my roof with their own Zamp controller and I have used my Zamp 200 watt suitcase with its own Zamp controller at the same time with no “fighting” noticed. This was during a dreary week of little solar gain and I decided to try it to see if it helped. I do have two 6 volt AGM batteries. I actually used this setup for most of the early 2019 months because the suitcase caught the earlier morning sun and the flexible panels caught the last rays of sun.

Tundra57 · July 2020

In my case, i had both my solar systems connected. My tab was a little shaded, so i expected the external solar would dominate. However after delpeting the battery some and turning on the 12v 3 way fridge the external panel solar was supplying 8 amps and the tab solar 0amps.

Now i know they should be different but since both controllers should be in the same mode and hence the same output voltage, there should have been some contribution from the tab solar.

It was explained on the victron website that if both controllers were on when the battery was fully charged (i think it was less than 2 amps being drawn) both controllers would go to sleep. When the voltage dropped enough for there to be a charge requirement one would wake up and one not.

This phenomena was noted and compained about by a number of owners.

Supposedly the synch software would wake up the sleeping controller so it would contribute.

I can't disagree with @plicato and his expert, but that is my experience. It follows other users complaints.

Supposedly if you have the BMV power monitor set up to communicate with the smart controllers then all is well.

I dont think they fight each other as charge voltage will dictate charge current up to the limitations of the solar setup. It was explained that this was peculiar to the smart solar units and their software.

I will know more when my BMV turns up and I install it.

plicato · July 2020

Thanks @Tundra57 for the clarification. My comment doesn’t explain the Victron weirdness you and others are experiencing.

Tundra57 · July 2020

@plicato roger. :-)

Sharon_is_SAM · July 2020

So, maybe a non-synchro portable controller is the answer?

Tundra57 · July 2020

@Sharon_is_SAM. I am beginning to think that two dumb controllers and a smart monitoring system would make more sense. But I'm already committed lol.

As long as I can see the controller has output I dont care what the solar side is doing. I can find that out with a multimeter.

But ill find out how well it works soon I hope. You know how unreliable Amazon has become.

BrianZ · July 2020

Like @ChanW, we also do not have multiple SCC's, but have the Victron with networked monitor and occasionally carry & use our solar panel on the TV roof. Because I'm also the driver, I haven't had the chance to monitor our system during travel like you have, @ChanW. However, while stopped at the dump station before heading home, I captured these screens showing our TV charging system & solar both charging the battery..

Image: https://us.v-cdn.net/5021717/uploads/editor/gp/gcq13lqkdp5r.jpg

What I don't know is how long this continued, and unfortunately, while we didn't have the fridge running on battery to really test it, it appears we might have had enough amps to do it, and maybe still charge the battery, depending on the sun. A panel with more than 100W might have been a better choice for this.

I also found the following performance characteristics curves for our Renogy panel..

Image: https://us.v-cdn.net/5021717/uploads/editor/jk/znd1eeg4gl3k.jpg

Which shows some useful info on the panel's generated voltage versus watts of power. This is useful when considered together with the following info from the Victron SCC manual..

Image: https://us.v-cdn.net/5021717/uploads/editor/2i/ifh0fum6q7d5.jpg

Sorry for the tiny print, but note the highlighted line stating that the panel voltage must exceed the battery voltage by 5V before the charge controller turns on; plus if it drops to less than 1V greater than battery voltage, it will turn off.
So, for example, if the battery voltage is 13.5V (receiving a charge from TV) and the panel voltage drops below 14.5V (around 75W on the chart), then it will turn off. And to turn back on would require 13.5V + 5V = 18.5V or the full 100W of power on the green curve. This might be difficult, depending on sun, clouds, angle of sun, etc, and would require less than full power without the car's charger attached.
We had hooked up the panel first, before starting the vehicle charger, so both were running fine when I captured those screens with both car & solar contributing. I hope to look at this again some day, but we mostly don'tdoffend on solar & I'd have to get my wife behind the wheel some day.

Looking forward to learning more about this from you all. 😉

MarkAl · July 2020

This is good data and I love this techy information. I too was concerned by the +5v before turn on and thereafter +1 before turning off. But then I realized that the open circuit voltage on the array (before a load is added) is 3 or 4 volts higher than with a significant load. So the "hysteresis" (+5 / +1) is needed to assure the panel will stay on when connected and loaded and the + 1 is a minimum the controller can "control" the charging of. I've been surprised that more of the 12V charging panels are not built with a larger open circuit voltage to allow a wider range of light intensity.

With clouds / trees hampering effective collection of energy it get's very confusing to design an efficient network to the software designers and users. Fortunately software is relatively easy to fix and update in the field nowadays. To our earlier question of whether to connect similar voltage panels together before the controller or buffer the outputs with a separate controller this issue alone may be a good reason. A problem with solar collection is that rarely all panels are equally exposed to the sun or have similar electrical responses in the best cases with a RV. A house is easier but talking to a friend who has designed and uses his own 10KiloWatt farm this problem is also not easy to always optimize.

networking mppt controllers

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