1 hour ago, The Terrible Triplett said:

Or one can think that the thing is, for most of us, the losses from the panels being too hot, clouds, smog / dust, all the connections over the system, fuses / cabling, inverter / MPPT efficiencies, chimney, leaves/ tree  etc etc etc brings the overall efficiency to about wot, 85% (?) over the entire system. So we nitpick X Y or Z ... does it bring it close to 100%, even 90%?

So I say, don't fret, just gooi (add) another panel and forget about it.

Ah!, there's a non-engineer in the house.

1 minute ago, phil.g00 said:

Ah!, there's a non-engineer in the house.

Ditto!!!

Therein the different perspectives I present to the other non-engineers. 😋

There is a time to delve deep.
There is a time to say whatever.

 

4 minutes ago, The Terrible Triplett said:

Therein the different perspectives I present to the other non-engineers. 😋

There is a time to delve deep.
There is a time to say whatever.

It's true, they say Rome wasn't built in a day.*

*( But, I wasn't foreman on that job).

On 2019/04/22 at 11:11 AM, plonkster said:

Oooh yay!

$ apt-cache search electrotech
qelectrotech - Electric schematic editor
qelectrotech-data - symbols needed for qelectrotech
qelectrotech-examples - examples files for qelectrotech

It's packaged already!

Fantastic drawing. Are we allowed to use this drawing for our own setup? Is it available in cad format please?

34 minutes ago, Russell said:

Fantastic drawing. Are we allowed to use this drawing for our own setup? Is it available in cad format please?

Yes use it. Sorry I don't have the original file.

Dear all, thank you for this very informative thread. One question please: Is the Venus GX an absolute necessity in the proposed Victron setup? (Grid tide but not necessarily feeding power back into the grid.) If I am willing to forgo the monitoring, what do I need to do the system (Multiplus 2 and MTTP 150/60) setup? Will be appreciated. 

31 minutes ago, Matthys said:

Venus GX an absolute necessity in the proposed Victron setup

Yes, it is the brains i.e. where the ESS software is installed on.

Thank you Triplett. Sorry for my lack of understanding. Thus to make ESS (An Energy Storage System is a specific type of power system that integrates a power grid connection with a Victron Inverter/Charger, Venus-device and battery system. It stores solar energy into your battery during the day, for use later on when the sun stops shining) working,  the VenusGX has to dynamically manage the Multiplus ii. Am I correct? 

16 hours ago, Matthys said:

... the VenusGX has to dynamically manage the Multiplus ii. Am I correct? 

Yes, that is correct Matthys. And thank you. 🙂 

But, like me, I keep batteries charged, for I don't want to use my small bank for that. So ESS has a few options.

On 2019/02/22 at 8:21 PM, The Terrible Triplett said:

On 2019/02/22 at 7:45 PM, phil.g00 said:

breach 50V in cold weather, somewhere in SA.

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

HOWEVER, it is best to be cautions. To run the larger 350w and the newer 400w (and even bigger ones coming) two in series - or go 250v MPPT if you must have higher volts.

Am pretty sure one of these years you will have very large panels and by fitting two in series they will be a perfect match for the 150v concrete ceiling of the Victron controllers.

But lets not deviate. This is a very very good exercise to show the importance of the Temp. Coefficient and the effect of that on MPPT's and warranties.

Thank you for a very informative thread.

In following the discussion on 2 panels in series or 3 in series for a 150V MPPT charger I notice that nowhere was the irradiance on the panel mentioned with low temperatures.

Canadian spec: 1:

 Electrical Data | STC*
CS6U 320P 325P 330P 335P
Nominal Max. Power (Pmax) 320 W 325 W 330 W 335 W
Opt. Operating Voltage (Vmp) 36.8 V 37.0 V 37.2 V 37.4 V
Opt. Operating Current (Imp) 8.69 A 8.78 A 8.88 A 8.96 A
Open Circuit Voltage (Voc) 45.3 V 45.5 V 45.6 V 45.8 V
Short Circuit Current (Isc) 9.26 A 9.34 A 9.45 A 9.54 A
Module Efficiency 16.46% 16.72% 16.97% 17.23%
Operating Temperature -40°C ~ +85°C
Max. System Voltage 1000 V (IEC) or 1000 V (UL)
Module Fire Performance TYPE 1 (UL 1703) or
CLASS C (IEC 61730)
Max. Series Fuse Rating 15 A
Application Classification Class A
Power Tolerance 0 ~ + 5 W
* Under Standard Test Conditions (STC) of irradiance of 1000 W/m2, spectrum AM
1.5 and cell temperature of 25°C.

But the rest (which isn't mentioned):

Electrical Data | NMot*
CS6U 320P 325P 330P 335P
Nominal Max. Power (Pmax) 235 W 239 W 242 W 246 W
Opt. Operating Voltage (Vmp) 33.9 V 34.0 V 34.2 V 34.4 V
Opt. Operating Current (Imp) 6.94 A 7.01 A 7.08 A 7.15 A
Open Circuit Voltage (Voc) 42.2 V 42.4 V 42.5 V 42.6 V
Short Circuit Current (Isc) 7.48 A 7.54 A 7.63 A 7.70 A
* Under Nominal Module Operating Temperature (NMOT), irradiance of 800 W/m2,
spectrum AM 1.5, ambient temperature 20°C, wind speed 1 m/s.

You will notice that the Voc is lower for 800W/m^2 than for 1000W/m^2. (That makes sense because as the irradiance becomes lower the Voc will drop.

To take it further: Panels installed (static) somewhere in the Kalahari at an angle of 25 degrees. Early morning it is not strange to measure -8degrees on a cold night.

But the angle of the sun at 9 o'clock  will be about 60 degrees. Thus the true irradiance on the panel will be 1000W/m^2(very optimistic) * cos 60 = 500W/m^2. My calculation (with 'n straight line calculated from STC and NMOT) is that the Voc will be about 37.8V at 25 C. At -8 C it will be 37.8 + 3.87 = 41.7V. With 3 panels you will still have a margin of 25V.

The coldest I personally experienced in the Kalahari was 10 C at midday on a cloudless day.

So the real question is: What is the real irradiance on the panel at the minimum temperature?

So I do not see in problem to strung 3 panels in series.

Hope I made sense.

Did I miss something?

 

I totally follow your reasoning - I went through the same thought process before deciding to install 3 x 330W panels in series with my 150V MPPT charger. However, I am in Cape Town so am not exposed to the same cold. My roof is also North-West facing, so only gets a relatively low illuminance first thing in the morning.

There is always the "worst-case scenario" where one has an unusually cold weather/snow event at mid-day and your batteries are full so are not pulling any current from the MPPT.  You then need to weigh up your appetite for risk versus the higher priced 250V MPPT 😉.

A famous saying comes to mind "In theory, theory and practice are the same, but in practice they are not". It may therefore be worth doing some tests with 2 panels in series to start off with.

1 hour ago, Matthys said:

Did I miss something?

What NigelL said: "In theory, theory and practice are the same, but in practice they are not."

What is you appetite for risk when you are talking temps as low as you get there in the Karoo? 🙂 
And then that one perfectly cold day with perfect sunshine and a cloud effect thrown in?

Series vs parallel = exact same wattage.
Only difference with parallel is it may need a wee bit thicker cable depending on the distance ... with no risk.

My highest voltage to date since last quarter 2018 using 3 x 350w panels in series in Cape Town has been 139.11v. 

1 hour ago, NigelL said:

I totally follow your reasoning - I went through the same thought process before deciding to install 3 x 330W panels in series with my 150V MPPT charger. However, I am in Cape Town so am not exposed to the same cold. My roof is also North-West facing, so only gets a relatively low illuminance first thing in the morning.

There is always the "worst-case scenario" where one has an unusually cold weather/snow event at mid-day and your batteries are full so are not pulling any current from the MPPT.  You then need to weigh up your appetite for risk versus the higher priced 250V MPPT 😉.

A famous saying comes to mind "In theory, theory and practice are the same, but in practice they are not". It may therefore be worth doing some tests with 2 panels in series to start off with.

I prefer to cater for worse case scenario's as well. We can't control, not predict erratic weather and I would rather be safe than sorry in this case. 

Point taken. Thank you.

On 2019/02/20 at 11:42 PM, The Terrible Triplett said:

As we build this list, we can add web links towards the end - easier to copy each time we update it.
 

Version 2: (versioning it will help to show which is the latest.)

Equipment:
Victron Multiplus II 48/3000 with MK3-USB cable (for firmware updates)
Victron BlueSolar 150/100MPPT with VE.Direct cable to VenusGX
VenusGX - ESS configured to grid tied
BMV-712 Smart with VE.Direct cable as well as cable for midpoint monitoring
VE.Direct to USB cable fir it one ever has to connect to the MPPT using VictronConnect

Optional:
Carlo Gavazzi with RS485 to USB cable 5m - nice to measure all the in / out of the main DB board.
Temp sense cable for VenusGX  to see the temp of the batts - nice to see the batt temps being recorded.
Battery balancers

Solar Panels - array optimally tilted due north:
Option 1: 8 x 350w Canadian Kumax panels - 2 series and 4 in parallel (To keep well within 150v limits)
Option 2: 10 x 350w Canadian Kumax panels - 2 series and 5 in parallel 
14 pairs of MC4 connectors
20m x 10mm2 Red & Black cable - can use 4 or 6mm, but 10mm is just the least amount of losses and the price difference is not that much
Additional 5m Red & Black cable for odds and sods connections
Panel frame mounts (IBR / Diamond Deck / Tile)

Batteries:
8 x Trojan J200RE's
Optional: Watering kit for the Trojan's. In their lifetime, the kit is a awesome time saver.

Wires needed - extra lugs as spares - assume 20m distance:
From inverter to batteries: 5m x 50mm2 red & black cable with 10 x 50mm/10mm lugs to crimp on
From MPPT to inverter: 2m x 25mm2 red & black with 8 x 25mm/10mm lugs to crimp on
Between batts: 30cm x 50mm2 black cable with 18 x 50mm/10mm lugs
22m Earthing wire: From panel frames to a earthing rod and inverter to DB board
Glands, Din Rail?

String Combiner Box:
1 x DB box
3 x NoArk 63A 1000VDC 6ka double pole breaker to break all 6 wires - or 2 x 4 pole NoArks.
6 x PV Fuse Holder with LED light - on all 6 wires
10 x 20amp fuses
1 x Citel Surge Protection DC/PV Type 2 1000VDC (DS50PVS-1000)

Fuse Box 1 - 25mm2 cable:
1 x 125amp fuse and fuse holder
2 x 125amp fuses

Fuse Box 2 - 50mm2 cable:
1 x 250amp fuse and fuse holder
2 x 250amp fuses

Ac_Out1 Always On DB Board:
Double pole breaker to switch DB off.
Earthleakage
Breakers for circuits

Tools:
1) Crimping tool - invest in the R500 - R800 jobbies to be set free
2) MC4 crimper to crimper
3) Multimeter to be able to test the volts
Optional: DC clip-on ammeter 

Hi Guys,

Please can someone explain the theory behind having NoArk 63A 1000VDC 6ka breaker on the combiner box if the if the max voltage on that PV string is only 150v? Most of the pre made combiner boxes seem to have smaller breakers like 250VDC.

I have ordered 3 x 500VDC breakers for my combiner box I could not find 2 pole 1000VDC breakers, will this still be ok? My PV Array is 9 x 350w panels 3 in series. 

 

3 hours ago, Kilowatt said:

I have ordered 3 x 500VDC breakers for my combiner box I could not find 2 pole 1000VDC breakers, will this still be ok? My PV Array is 9 x 350w panels 3 in series. 

If it is DC rated for that voltage... then no problem.

9 hours ago, Kilowatt said:

Please can someone explain the theory behind having NoArk 63A 1000VDC 6ka breaker on the combiner box if the if the max voltage on that PV string is only 150v? Most of the pre made combiner boxes seem to have smaller breakers like 250VDC.

One can spec the parts to the n'th degree saving a few rand here and there.

But I got tired of the finer calcs. So one day I sat down and decided that X part should ideally be able to be used for 12v / 24v / 48v system or 150v or 250v Pv or maybe one day I do go off the rocker and go for a 600v PV system.

The fuses on the other hand, that ones needs to spec properly, but as above, if the system changes voltages, I should just change the fuses, not the holders.

The NoArk breaker, for me, is to switch off the panels.

Edited May 12, 20197 yr by Guest

I made the most fundamental mistake in planning more panels, in the geyser thread, to move from EV to grid tied geyser heating.

How, quite easy. 🙂 

Lets take this example.
The KIT:
3.5kw array - and it is a amazing good day so the Canadians generate 4kw for an hour say.
3kva (2.4kw) Multiplus II / Mutligrid

Loads:
Lets say the load is 3kw.

How much of the load will be provided from the panels?
Potential of 4kw with the load of 3kw so I have 1kw spare? Nope. Does not work like that. 

How does it work?
With batteries left on "Keep fully charged", load of 3kw? Of the potential of 4kw from the array, the system will use a whopping 2.4kw ONLY of the panels.
With batteries needing charging? If the batts need a lot of charging, load of 3kw, only THEN will it reach the potential of the 4kw array i.e. 2.4kw to the loads and 1.6kw to the batteries IF the batteries can take it.

Although the MPPT can produce the full 4kw, the power must go somewhere.
The inverter - and this goes for all inverters - can only generate the max it is rated for, derating at higher operating temps like in a garage / cupboard, so the 2.4kw in the example can go lower at higher temps.

So, what now?
Do I keep the 2.1kw array, up it to 2.8kw or do I stick to (WANTS) 3.5kw?

After a LOT of arguing in my head, I am going 3.5kw because:
1) I will have the loads covered better in winter - seeing as all the geysers are now going to be heated, on timers, via the grid tied system.
2) Going above 3.5kw I cannot see usefull - 500kw avergae daily load and 2kw for the geysers each - timed well.
3) And I will get lithiums (24v) (o used the dinges out of them) once I find them at a price I find acceptable when the T105RE's reach EOL - for now they must be kept charge for Eskom issues - so I accept the losses.
4) And the price to install more panels later will cost more - so rather do it now for the batts are going to be replaced.

Or I go cheap skate and use 4 x 200ah truck batteries, use them to 20% DOD and basta with expensive banks. 🙂 

Edited May 25, 20197 yr by Guest

On 2019/02/20 at 9:31 PM, The Terrible Triplett said:

6 x PV Fuse Holder with LED light - on all 6 wires

Morning TTT, I also got some "Fuse Holderswith LED" at ACDC but for some reason I don't see any LED on with my current system,

I need to take it back for a refund, where did you buy yours

 

15 minutes ago, Samsed said:

... where did you buy yours

Bought mine from Rubicon.

Sharing my thoughts with a new PF member, a penny may have dropped with this endless debate which one is more cost effective, Axpert or Victron?

Do we actually consider the full picture, seeing that grid tied is very very new in SA, rife with SANS and NRS debate (read emotions) and some may not fully understand the pro's of going grid tied?

Over 1 year, 5 years, x years, which one is actually more cost effective? 5kva Axpert (off-grid) or 3kva Victron + MPPT + VenusGX (grid tied)?
Considering the larger battery bank required for any off-grid system - and the replacement costs of it.
Versus a smaller bank needed for "Always on Loads" on a grid tied setup.
AND the fact that with grid tied, even with a 3kva unit, you start offsetting your Eskom usage from the very 1st watt in the mornings to the last watt evenings, every single day.
Not forgetting that even on rainy / cloudy days, with a grid tied setup, the watts are still being off-set against Eskom units bought versus off-grid needing those watts to recharge the batteries.
And not forgetting replacement / repair costs - everything breaks eventually - so the warranty on the equipment is a very important factor.

Which ones saves you more, 5kva Axpert off-grid or 3kva Victron grid tied, over 5 years?

Keeping in mind:

10 minutes ago, plonkster said:

1) still has the float bug, still needs to get firmware from some enthusiasts down in the way south,
2) still doesn't do decent SOC and
3) needs extras for those too, needs 3rd-party monitoring stuff that's not precisely cheap anymore.

Edited May 31, 20197 yr by Guest

Case point.

It is cloudy outside, clouds come and go, yet right now whatever the panels CAN produce, is being pushed into the home, a whole 258watts from the panels.

These little titbits added into the house overall usage, over say 5 - 10 years - not wasted on off-grid charging of batteries, must be contributing to a rather huge saving on the big picture, no? 

 

 

And a few minutes later ... as the clouds move ... 

Edited May 31, 20197 yr by Guest

21 minutes ago, The Terrible Triplett said:

Which ones saves you more

The big guy at SolarMD (they are really big on Axpert of course) once remarked to me that there is one very obvious cost saving measure that many MANY people miss (props to that guy for being this open minded!). A 3kva Multi has a no-load draw of just 11W. A 5KVA Axpert has a no-load draw of around 50W. Sure, I know it's a bit apples and oranges (3kw vs 5kw and all that), but I also know many people buy the 5kva Axpert not because they need 5kva... but because that's the smallest 48V unit they even make.

Now consider what the difference of around 40W no-load draw does overnight and how that impacts battery size. Over the 15 hours or so in a day (say from 5pm to 8AM the next morning) when you're partly or fully on battery power, that's at least 600Wh or around 5k of battery value 🙂

But again, I need to reiterate: There's an old financial rule of thumb that if you can postpone an expense (at least without significant additional cost), you should do so. It almost always makes sense. Despite that, I still prefer nicer stuff... right now I'm in the market for a nice small SUV... and I can tell you it's probably not going to be a Haval 🙂

5 minutes ago, plonkster said:

Over the 15 hours or so in a day (say from 5pm to 8AM the next morning) when you're partly or fully on battery power, that's at least 600Wh or around 5k of battery value 🙂

600Wh "lost" on top of the watts being fed overall into the home IF the inverter is grid tied, I think maybe we are onto something here.

14 minutes ago, The Terrible Triplett said:

grid tied

Yeah it depends a little. Using my own place as an example: At night (after going to bed) my loads are low enough that I can cover all of it from battery. So whether it was running grid-tied or not doesn't matter so much. But the moment you have larger loads, then you either need a battery that can power them, or you need to accept that your quasi-hybrid inverter (which switches fully to the grid at these times) might lose you a bit of self-consumption. That means 1) batteries work a bit harder if you don't have a hybrid inverter, and 2) you sort-of have to make them large enough for most loads but small enough to fit your wallet. So the cheaper inverter definitely increases the cost of the battery, there is no doubt about that. The challenge is to find out by how much.