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Victron grid tied setup from scratch


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19 hours ago, phil.g00 said:

So splitting the difference a 4 kW array would seem not far off the mark.

My approach would be to say:
Option 1: You can go all out and get a 4kw array and 150v / 250v MPPT day one.
Option 2: Or you can go 2kw then another 2kw checking your data over a few months / year till one hits the sweet spot for where you are based on ones own needs.

Therein the point of making sure the size panels one uses, are still available in time.

Or the budget conscious outside the box thinking way:
Option 3 : Smallest 48v is 150/35 so do it in 2kW array increments at wot, R4.3k per MPPT.

This option is interesting in not only price, expanding over time with no worries re. the same panels available, but you can position the 2kW array additions optimally like one facing morning, the other afternoon - or any other combination one wants.

And if 4kw is not enough, add another 150/35 much later so now you have 6kW - if you want.

Cost effective flexibility if you ask me.

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4 minutes ago, The Terrible Triplett said:

My approach would be to say:
Option 1: You can go all out and get a 4kw array and 150v / 250v MPPT day one.
Option 2: Or you can go 2kw then another 2kw checking your data over a few months / year till one hits the sweet spot for where you are based on ones own needs.

Therein the point of making sure the size panels one uses, are still available in time.

Or the budget conscious outside the box thinking way:
Option 3 : Smallest 48v is 150/35 so do it in 2kW array increments at wot, R4.3k per MPPT.

This option is interesting in not only price, expanding over time with no worries re. the same panels available, but you can position the 2kW array additions optimally like one facing morning, the other afternoon - or any other combination one wants.

And if 4kw is not enough, add another 150/35 much later so now you have 6kW - if you want.

Cost effective flexibility if you ask me.

I am open to multiple MPPTs if they come in cheaper than 1 big one.

It will probably mean an extra 2K or so on copper with the cabling if we drop the voltage, so factor that in.

If 2 x smaller MPPT +2K <= 250/85 price, then I'm agreeable, and we can resize the cabling.

But I am loathe to skimp on the overall actual energy source of the system, I really think we should cost out a balanced system without a bottle-neck.

We should still present a final destination, people are wise enough to fill in their own stepping stones according to their individual budgets.

 

 

 

 

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4 hours ago, phil.g00 said:

, Am I correct that the Multi-plus II can limit feeding back into the grid and know the SOC direct from a BMV without a Venus device?

Unfortunately not. The Venus device runs both the ESS control loop and is responsible for shoveling data between devices (eg an SoC value from the BMV to the Multi).

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@plonkster & @The Terrible TriplettI found this on the WWW, and I populated with some figures, you may want to have a play.

I tried to emulate two types of loads, namely a small constant base load, and an average peak load that our man will pile on during the solar window.

I picked "0.1" of a day for load-shedding back-up ( 2.4hrs), which I think we're all agreed on.

I also made the assumption of a 600kWh/month user, which I think is fair because the CoCT also assumes the same fair-usage billing threshold.

This is normally used to predict the battery bank and inverter-size necessary from a list of household loads on the "Electrical load" tab.

When the inverter size (2.4kWh) and the battery size (400AH) are a given as in our case, it is quite illuminating reverse-engineer  these back to loads though with different size arrays.

Incidentally, it also is very illuminating when you start using Lithium DOD's and efficiencies as compared to LA.

 

 

Solar-Panel-Design-22-8-12.xls

Edited by phil.g00
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On 2019/02/22 at 8:21 PM, The Terrible Triplett said:

My panel installer, with all his experience, said not a chance in Cape Town for the 350w.

So now I’m paying attention.

My inverter max voltage is 500v. I was going to use 10 of the Canadian Solar 350W panels which makes a max VOX of 462v.

Cape Town.  Do I need to go to the 330w panels, or use 9 not 10?

Thanks

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2 hours ago, Elbow said:

 Do I need to go to the 330w panels, or use 9 not 10?

Note: Even with my installer saying not a chance, the onus is still on my head.

Which panel size matches your MPPT the best?

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3 hours ago, Elbow said:

Cape Town.  Do I need to go to the 330w panels, or use 9 not 10?

Well... I'd say just go with 9 panels and bob's your uncle. There's like an 0.3% per °C difference in voltage as you go up from 320 to 335 or from 335 to 350, so going a panel size smaller buys you only a little, but removing a whole panel gives you a whole 10%.

At 9 vs 10 you're at much less of a disadvantage then us folks with a 3 vs 2 scenario (we lose a whole third of the voltage benefit, you lose 10%).

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4 hours ago, Elbow said:

Do I need to go to the 330w panels, or use 9 not 10? 

Looking again at the spec sheet of the Canadian solar modules, they list different open circuit voltages at 25°C (you get an extra 0.3V or so for every 20W), but the temperature coefficient is pretty much the same for all the models at 0.31% per °C. If the smaller modules had a better temperature coefficient it might make sense, but as it is you're buying around 3V extra space with the smaller modules (10 x 0.3V), which is 0.6% of the open circuit voltage, and gives you 2°C extra at the bottom end. So you go from being able to handle -3°C with the 350W module to being able to handle -5°C on the 325W modules. So I think the answer is clear: Go with 9 panels. Then you're safe up to New York Blizzard levels.

Edited by plonkster
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29 minutes ago, plonkster said:

Then you're safe up to New York Blizzard levels.

And yet, as you said, there are a lot of rooftop solar water heating equipment all over Cape Town - equipment that do not like water to freeze. 🙂 

Tough one to say what others should do.

 

Me, as I have the 350w ones (3 series and 2 parallel) , if I need more watts, two options on the 150/100 MPPT. 
3 in series and 3 in parallel - 3150 Wp
Or basta the volt drop, 2 x series and 5 x parallel - 3500Wp

And if I was on 48v, same controller, 3 in series and 5 parallel - 5250Wp

Or, TTT style, sell the 6 x 350w one day and get >=400w panels - where with 2 in series the volts are acceptably close to the max of 150v yet nowhere near the max. 🙂 

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Had to quickly go and drive a truck for someone.

I'll catch up here soon and summarise where we are at.

Driving trucks on a VAT invoice adhoc basis when a driver got sick or whatever.

IT guy driving trucks - explain that! 🤔
It is a hobby - new one I'm learning the ropes of fast.

Like this one yesterday. That 8 speed split gearbox Mercedes is old tech, but I like it. YOU drive it, not a computer like in the automatic UD's.

The cooldrinks are offloaded by 3 guys by hand on a trolley. Respect for THOSE guys I tell you!

image.thumb.png.c183d98991316ae2d6871a11a42e7193.png

 

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1 hour ago, The Terrible Triplett said:

That 8 speed split gearbox Mercedes is old tech

The one with the splitter on the diff? My dad had an old Isuzu with that setup. 4-speed and reverse up front, splitter on the diff, double de-clutch shifting. You really only used the bottom 4 gears (low-range on the splitter) if you were hauling something. It also had a neat feature where you could flip the splitter and kick the clutch to go to low-range. 1970s tech...

Edit: Come to think of it, he also had a Bedford from the 1960s with pretty much the same setup. The one with the bulbous nose.

Edited by plonkster
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Hi,

I would love some advice from you guys. I currently have a Multi plus 48/5000/70 and a very small battery bank. I would love to do something similer to the above. Most my power usage is during the day and I want to lower my eskom bill, but still have grid for heaters at night. To add to the issue also want the panels to produce during outages. 

Can it be done, or should I just buy a Goodwe hybrid ?

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1 hour ago, Monroe said:

I would love to do something similer to the above.

Do you have a CCGX or a Venus-GX control unit? Cause that is all you really need to run ESS. It is also handy to have an MK3-USB dongle for the programming, but sometimes you can beg, borrow or hire an installer for the once-off work.

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39 minutes ago, Monroe said:

only the old Victron and batteries

OK, the first thing you must do: Find out what CPU is used in your unit. Easiest is to unscrew the front panel and look at the sticker on the main board, it will start with either 19 or 26. If it starts with 19, then it is too old to do ESS. If it starts with 26 you're good. If you bought it after 2015, it should be the new CPU.

Then at a minimum you need a Venus-GX of a Colour-Control. Or you can roll your own on a raspberry pi, but that is another topic. Once you have that you can run ESS, where it will attempt to keep the input at zero, power the loads from solar/battery, and fall back to the grid if it has insufficient capacity or the batteries go to low.

Then you can decide if you also want to feed power into the grid to compensate for loads that are not on the output of the Multi (typically a geyser or a pool pump). If you want to do that, then you need a Carlo Gavazzi energy meter (ET112 if it is single phase), and a USB-RS485 cable to connect it.

Edit: You will also need to do a firmware update on the Multi, assuming it has the new CPU. For that you will need the mk3-usb dongle.

Edited by plonkster
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Well I have popped the champane, I am lucky. It is does start with 26.

So will need to purchase  what you mentioned and I guess a MPPT.

I am in the Randburg area, could you recomend someone who could connect, program and update the firmware ?

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11 hours ago, Monroe said:

I am in the Randburg area, could you recomend someone who could connect, program and update the firmware ?

OK, I don't know this guy from more than a single phone call, but he is listed as a trusted installer on victronenergy.co.za, and he is in your area and quite passionate about the brand:

JOUBERT ELECTRICAL, Adriaan Joubert, 082 823 0761

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