@The Terrible Triplett

1. The input voltage capability of an MPPT should be avoided with a margin for error. -  absolutely agreed this determines the number of panels in series.

And I also matched my perfectly tilted true North facing panels to never over-power my MPPT's.

And it gives me a big peak of power in the middle of the day and my MPPT has to be able to deal with that.

And to provide the perfect angle and direction for the panels cost a lot of time and  money in steel and labour.

Rookie mistake,  with the relatively cheap price of panels, when I have so much imperfect roof space.

I have a large standing load, and I want more power all throughout the day.

So without the  cost of the special towers and frames I am now adopting another approach, more panels and using the opposing slopes my roof.

And this may not apply to you, but a lot of people have peaked roofs that aren't the perfect direction, so it's not a rarity.

The panels can now be played with, but I will qualify that statement with respect to PV strings on a single MPPT.

It is often said that all panels going into an MPPT must be the same direction and angle, this is true for all panels in the same series string. 

It is however this not true for all strings in the array to a single MPPT.

A second parallel series string can be facing another direction and a different angle and yet go into the same MPPT without a negative effect.

This is because voltage output is still high with a little light. Even though it is may not be able to match the same current output as the parallel string, it wont pull it down.

This effect can be used to advantage to pair an East facing string with a West facing string so as to get a longer solar day in such a way that more panels wont exceed the MPPT's specs even at solar noon. 

The aim being to keep acceptable production going from earlier until later in the day but still within spec, and actually producing more kWh throughout the length of day by flattening the midday peak. 

I certainly intend to over-panel a PV inverter I will be getting soon to take advantage of this.

(Mind you that particular inverter's built-in MPPT's can accept an very wide input voltage range, so there is more flexibility).

Here is someone from Oz who has done a couple of tests:

https://forums.energymatters.com.au/solar-wind-gear/topic5064.html

 

Edited November 28, 20187 yr by phil.g00

4 minutes ago, phil.g00 said:

And this may not apply to you, ...

For a very long time I had a 400w array on a 75/15 and a 930w array on a 150/35, both controllers programmed identically being on the same battery bank.

The 400w array was more aligned for the winter months, the 930w array for summer, the 400w being an adjustable array - till the roofs height made it a pain.

First off-grid then grid tied for a couple of months, comparing the data, with ESS the difference in production was immense, all the power is used in the house versus off-grid, only what is needed. Today I won't go off-grid again where there is Eskom, and I can legally grid tie. 

And I saw how far one can get with a 1.1kw array. From +-R1200 pm down to +-R800pm, just because of ESS. Now I want to see what 2.1kw does.

You may wonder, but he has 1.33kw potential?
The 400w array regularly delivered the near full potential, the 930w array was on some pretty old (read very expensive at the time) wiring, so I seldom got the full value from them. 

In my experience, as you say say @phil.g00 , having panels purposefully positioned with thought, to cover loads i.e. focus on mornings, afternoons, middle of the day or restrictions due to roofing constraints, becomes so easy today with the cost of panels IF one uses separate programmable controllers.

My roof is ideal for mornings till late afternoon, I was contemplating having a dedicated 700w for mornings only ... till I got gatvol with the detailed analysis. Sometimes a shotgun works as well. :-) 

Yes, I am going to be banging up panels wherever there is a patch of roof from now on, I'll try to mirror it with another appropriate string. 

But panel placement will dictate the ancillary equipment and it wont be the exact science of the panels that went before.

I see a pallet of panels coming a year for the foreseeable, but I've got over 200kWh/day average grid usage to eat into.

And there is a power cut every thunderstorm.

Presently the system is not grid-tied, I am just taking blocks of load off-grid. Eskom is feeding the rest.

I don't think I have a hope of ever being legally tied to the grid considering I have set my sights on about 30kW of inversion capability over the next 2-3 years.

But we shall see, the way ESKOM is going I might get a phone call to help out.

1 hour ago, The Terrible Triplett said:

with ESS the difference in production was immense

I do realize being grid-tied would be a game-changer, but also the bigger the system is the more flexible it becomes, with regards to peaks loads.

I also intend to liberally deploy CBI energy control units, day/night switches and astronomical timers to manage maximum demand.

But you are right ESS is still better.

 

 

Edited November 29, 20187 yr by phil.g00

6 hours ago, The Terrible Triplett said:

When you oversize it, and both Victron SA and the dealer categorically told me ... Don't. Do. That. Ever.

Not to worry, no over sizing here, both my options are Accepted. 

6 hours ago, The Terrible Triplett said:

So guys, use this, or not, me, I am keeping well within the published specs so that the controller can serve me for a decade or more.

Fully agree......... no need to oversize......... wont benefit you one bit.

Another titbit I learnt recently when I asked the question, can I?

Each and every person asked me for the panel specs, specifically asking to see the V temp coeff and I temp coeff of the panels. One can load the values for ones particular panels, in the Excel document, under Modules.

The Victron Calc tool, actually goes for all the tools out there, really need those values to calculate properly, especially if where one is, temps can get low, or below zero.

I captured the panels I was looking at, mixing and matching, results where interesting, with the 350w panels priced really good per watt, so I had to be very careful.

That same sample above of pushing the envelope on 2100w, using the Victron panel temp values, gives a different result as the Canadian Solar panels are -0.29 and 0.05 and not -0.34 and 0.037, as per most of the Victron pre-loaded panels are. See:

The Victron dealer I spoke to at length, on all his sites, they stay about +-20% below the max values of the controllers as a rule of thumb. 

Over-sizing in the Northern hemisphere makes complete sense as the ambient temps are cool with less sunlight for shorter periods. 

And to solve a heat problem caused by oneself, easy. Just put 24v bus ventilation fan underneath the controller/s ... it works, even if the ambient temp where the controller/s are mounted, reaches 32 deg Celsius.

One like this ... :-) (had it spare, if ever I want to cool things down. )

 

And on ESS, on the controller/s, run this command each time the VenusGX reboots:
dbus -y com.victronenergy.system /Debug/BatteryOperationalLimits/SolarVoltageOffset SetValue 1

Setvalue 1 is 1 second, what I use. Makes a HUGE difference in the production. @plonkster can explain the tech side in more details on why.

Edited November 29, 20187 yr by Guest

32 minutes ago, The Terrible Triplett said:

Another titbit I learnt recently when I asked the question, can I?

Just for your piece of mind...... Still accepted........ 

16 minutes ago, The Terrible Triplett said:

Setvalue 1 is 1 second, what I use. Makes a HUGE difference in the production. @plonkster can explain the tech side in more details on why. 

It is one VOLT. This is how it works:

1. You need to have DVCC turned on. Long story around that, for now just accept that it won't work without this.

2. You need to set ESS mode to "Keep Batteries Charged".

3. The Multi will then instruct the solar chargers to charge at a higher voltage than it charges at itself. This prioritises solar power over grid power.

4. When the battery voltage exceeds the voltage the Multi is configured for, it will start sucking energy from the battery to hold the voltage down. This energy is then fed into the grid. In other words, it applies a slight overvoltage.

5. If you enable "Feed-in excess solar power" on the ESS menu, then it feeds all this power into the grid. If you don't enable that, then it limits the amount to your loads.

6. The voltage offset it adds is 0.1V for every 12V increment. So on a 48V system it is 0.4V, on a 24V sytem it is 0.2V.

7. To improve feed-in, you can increase the offset with the above command. This adds another 1V to it, so in TTT's case the solar chargers charge 1.2V higher than the Multi.

8. This does however mean that if your loads are less than the production, your batteries will be charged higher than normal. This is not a problem in most cases, at least, it is usually much less of a problem than people think.

9. There is still a bit of work going on on this feature. The 0.1V/12V number only really works well if the voltage drops on the cable is low enough, and if the devices are closely calibrated. In rare cases it might not be. Normally this is solved by turning on shared voltage sense (which essentially takes care of calibration issues and voltage drops), but again causes trouble in a small minority of cases (pylontech... which has a margin of only 0.8V between charge voltage and the Oh-SH*t-switch-everything-off-now! point.

Soooo long story short. You can either turn on shared voltage sense, or you can play with TTT's command above.

@plonkster, one supplier tells me that the MultiPlus, Multiplus II , Multigrid and Quattro comes with a build in MPPT thats why its called a Inveter/Charger.

Non of the data sheets show any Solar charge controller anywhere. 

To my knowledge, Except for the EasySolar range an inverter is not bundled with a MPPT. For all the above mentioned a separate MPPT is needed. 

10 minutes ago, Jaco de Jongh said:

, one supplier tells me that the MultiPlus, Multiplus II , Multigrid and Quattro comes with a build in MPPT thats why its called a Inveter/Charger.

That supplier is wrong :-)

It is called an inverter/charger because it can charge from the grid. Normally an inverter cannot do that, it can only DISCHARGE the battery (and make AC from it). It is called an inverter/charger because (unlike the Phoenix) it can also charge :-)

The EasySolar is the only one with a built-in MPPT. And as I said earlier, it's really two devices built into one enclosure (and the same is technically true of the Axpert). If you open it up and look inside, that is what you will find. From the software side, they look like two devices too. On VRM, it shows up as two devices. The EasySolar is meant for small house setups, boats, campervans, because of the neat packaging. For larger installs the only advantage is price.

There is a new EasySolar coming soon (based on the Multiplus-II) that will pack an internal Venus device (just like the 5kva has now, but less expensive). It will fit somewhere between the CCGX (full LCD screen) and the Venus-GX (no screen at all). It is based on the nanopi. It will have a small LCD display for some basic info, but it will have the usual web interface you get with the others. This would be ideal for you... but I don't know when that will be officially released. Early next year I think.

16 minutes ago, plonkster said:

It is one VOLT. This is how it works:

1. You need to have DVCC turned on. Long story around that, for now just accept that it won't work without this.

2. You need to set ESS mode to "Keep Batteries Charged".

3. The Multi will then instruct the solar chargers to charge at a higher voltage than it charges at itself. This prioritises solar power over grid power.

4. When the battery voltage exceeds the voltage the Multi is configured for, it will start sucking energy from the battery to hold the voltage down. This energy is then fed into the grid. In other words, it applies a slight overvoltage.

5. If you enable "Feed-in excess solar power" on the ESS menu, then it feeds all this power into the grid. If you don't enable that, then it limits the amount to your loads.

6. The voltage offset it adds is 0.1V for every 12V increment. So on a 48V system it is 0.4V, on a 24V sytem it is 0.2V.

7. To improve feed-in, you can increase the offset with the above command. This adds another 1V to it, so in TTT's case the solar chargers charge 1.2V higher than the Multi.

8. This does however mean that if your loads are less than the production, your batteries will be charged higher than normal. This is not a problem in most cases, at least, it is usually much less of a problem than people think.

9. There is still a bit of work going on on this feature. The 0.1V/12V number only really works well if the voltage drops on the cable is low enough, and if the devices are closely calibrated. In rare cases it might not be. Normally this is solved by turning on shared voltage sense (which essentially takes care of calibration issues and voltage drops), but again causes trouble in a small minority of cases (pylontech... which has a margin of only 0.8V between charge voltage and the Oh-SH*t-switch-everything-off-now! point.

Soooo long story short. You can either turn on shared voltage sense, or you can play with TTT's command above.

This is a bit confusing. 

In short, the Victron Hybrid will do what every other Hybrid will do?

1. It will charge the batterys according to the "priority" settings?
2. It will take extra available PV and reduce your consumption from the grid?. 
3. It will only feed back to grid if you allow it to do so.. ?

If I sum this up correctly, It will be very difficult to use the 6kw of panels on the roof to supply 5kw of load once my battery's are full.  From what i see above there should be some kind of a balance (one that i am still struggling to understand the logic of)

35 minutes ago, Jaco de Jongh said:

Just for your piece of mind...... 

I have no peace of mind at play here. The info I am sharing is for general consumption, use it or not. 

 

33 minutes ago, plonkster said:

It is one VOLT.

Sorry, typo, saw it too late, could not fix it. It is easier to type 1 than 0.2 :-) 

Charging is maxed at 29amps - 13% of the batts ah. 

33 minutes ago, plonkster said:

You can either turn on shared voltage sense, or you can play with TTT's command above.

Feed-in excess solar power

Share voltage sense is on.
Feed-in is off.

The difference between not setting it, and setting it, is rather huge. I can post values, or Victron can look at my site and use it as a test. They have access.

Edited November 29, 20187 yr by Guest

1 minute ago, plonkster said:

That supplier is wrong :-)

Thanks, I didnt want to argue with an supplier without confirmation. 

1 minute ago, Jaco de Jongh said:

If I sum this up correctly, It will be very difficult to use the 6kw of panels on the roof to supply 5kw of load once my battery's are full.  From what i see above there should be some kind of a balance (one that i am still struggling to understand the logic of)

The key here is the term "Self Consumption". You want to use as much of the power you generate yourself, usually because there is no or little benefit in feeding it into the grid. This means using the batteries to "ride out" times when there is no solar production. In Victron parlance, this would be when you set the ESS mode to "Optimised". This is by far the best mode to use in my opinion, it gets the best self-consumption. You set a minimum SOC, and the battery is never discharged below this point (unless the power fails). So battery capacity ABOVE this is used for self-consumption, and battery capacity below it is used in emergencies.

There is however a second mode, called "Keep Batteries Charged". In this mode, the battery is always kept at 100% (like a UPS), but PV power can be used to power loads. Self-consumption is generally not very good, because if there are no loads to consume the power, then the MPPT simply throttles it away.

TTT is being very careful with his batteries, because they are a somewhat "bejaarde" set of Trojan T105s. That is why he prefers this mode.

If you have LFP batteries, and you intend cycling them daily, then none of what he wrote matters. You won't be doing that anyway...

I run my system in optimised mode, taking the batteries down to 55% SOC at night. It depends on the time of the year too, and I generally watch the weather report too and might set it higher if tomorrow there is rain.

40 minutes ago, plonkster said:

TTT is being very careful with his batteries, because they are a somewhat "bejaarde" set of Trojan T105s.

Since day one on Self Consumption. Keeping them charged only if there a power failures.
Keeping them charged is wasting a wee bit of power.
And If there are clouds, tough solar day, then I switch on Feed Back ... THEN it goes full tilt!
I monitor that for my meter does charge me for that .. so I lose a few cents now and then ... bleh.

SOC on old array was set at 95%. New array 80%. 80% being the golden spot for T105RE's.

Because on the old array it took time to recharge, ESS sorted that nicely, for being on 1.1kw, most of the time all the power was used in the house, therein the 95% SOC setting.

And that is also a nice little titbit for newbies. You can start with a smaller array and bank, tweak the shiite out of it, learn, study the data ... and then add on based on where the power is needed.

Ps. They are not "bejaard"! Wot, 3 odd years old ... early "twenties" if you ask me ... hardly been used. 

Note: The above is for all Trojan users only. Will sell my 24v Multigrid one day and go Multiplus II 48v with Polys ... once the T105RE's are over and done.

Edited November 29, 20187 yr by Guest
Add a few more ideas.

I should be the proud owner of the following blue equipment if all goes well before the end of next week.  Should have it on the wall shortly after. And maybe I can get a good nights rest before Christmas............ 

Ziehl to be added soon. 

1 x 8000VA, 48 volt....

2 x SmartSolar 250/70 MPPT

1 x Venus GX

 

52 minutes ago, Jaco de Jongh said:

I should be the proud owner of the following blue equipment if all goes well before the end of next week.  Should have it on the wall shortly after. And maybe I can get a good nights rest before Christmas............ 

Ziehl to be added soon. 

1 x 8000VA, 48 volt....

2 x SmartSolar 250/70 MPPT

1 x Venus GX

 

Good choice!!! 

@plonkster, this should be my last question on this thread. Comms is still confusing me a bit. 

I will have Ve- direct on both Charge controllers as well as Ve-direct on the BMV 712... I guess the Ve direct to usb will no longer work inthis setup so I will need 3 of these..  

Problem is I can only see 2 inputs, but three device. Can 2 devices rur in parallel on one input and still do what it is suppose to. 

Is the Ve-bus part of the VE-direct? And what cable can be used for connecting the Quattro to the GX?

If i understand this correct, once connected to the gx , configuration to all these devices is possible remotely, and no additional cabling in needed for connecting all the component to a laptop or PC for first config... 

 

You are correct there are only 2 Ve-direct inputs on the Venus.

There is recently launched product that is said to handle multiple MPPT Ve inputs called the OCTO. Maybe tha's what you need?

1 hour ago, Jaco de Jongh said:

I guess the Ve direct to usb will no longer work in this setup

I think you can also connect Ve devices via usb to the Venus. (apparently up to maximum of 6).

14 minutes ago, phil.g00 said:

I think you can also connect Ve devices via usb to the Venus. (apparently up to maximum of 6).

Actually after reading the bugfix page it appears that now up to 20 or more can be connected, but don't ask me how.

https://github.com/victronenergy/venus/issues/130

1 hour ago, Jaco de Jongh said:

I guess the Ve direct to usb will no longer work inthis setup

No man...

:-)

You plug two of the vedirect device into the vedirect ports, and the third one goes into a USB plug (it has two) using a vedirect-usb cable. If you need more than two USB devices, add a USB hub. You can add as many as you want, although each one adds a bit of CPU load and it runs out of steam at some point, around 20 devices or so, but probably more like 10.

That digital TX cable you listed is for something else. That's for things like the street-light function (where the MPPT can turn on a load for a number of hours after sunset).

Remote configuration of vedirect devices is a work in progress, some of the support is there already (the vedirect_interface and mqtt-rpc components are done, but the rest of the pipeline is still being built).

22 minutes ago, phil.g00 said:

I think you can also connect Ve devices via usb to the Venus.

Seems like this might just be the case, if so, I am sorted... BMV to usb port, mppt to each Ve direct and Quattro to VE-bus

 

9 minutes ago, plonkster said:

You plug two of the vedirect device into the vedirect ports,

These two also VE-direct to usb?  Forget i asked, think I found the right cable. 

And what about the cable for the Quattro. so many products, I will know after this exercise but man its confusing.. 

Think I have got the one: For the VE-Direct ports. 

 

Some detail again. Vedirect is really just TTL-level serial comms. The little white VE.Direct ports are TTL-level serial ports. The ve.direct USB cable is essentially a USB-serial converter with galvanic isolation built in. So when you run out of vedirect ports... you can add more using USB cables.

That is why the straight vedirect cable is essentially a straight-through 4 wire thing. 3 of the wires does the usual: Ground, TX and RX. The fourth one is  power supply... which is needed in some cases for a power supply (due to metioned galvanic isolation).