Hello, first foray into the victron forum, hope I didn't miss a post which covers this, I have done some searching but didn't find it which surprised me. Hopefully someone else has been down this path too
I've been trying to work out feasibility of using Victron kit for grid-tied domestic solar PV installation, with ESS, either easysolar or quattro/multiplus. I'm not familiar with "the Victron way" of thinking about these problems, there may be something obvious to Victronites (correct word ?) which I'm missing!
A long post which is in essence quite simple - which route for inverter and battery makes more sense and did I miss a possible different way to do this ?
Thanks for taking a look at this post, any suggestions welcome, I may take a while to come back to this as life gets in the way at times! Apologies if this post is too long and bores you to death ;-)
Application & usage
Solar PV, with battery storage and EV charging
- Roof surfaces are approximately East-West, about 10deg more to the east
- Present usage is 4000-4200 kWh per year.
- Anticipate will have to get an EV at some point in next few years, maybe <2yrs.
- Immersion diverter likely
- No use of heat pump
- Do not expect to be off-grid except during power cuts or due to inadequate electricity supply infrastructure.
- Some semi-critical application : maintaining supply to medical equipment overnight (2.5A/240V on a standard plug) and supply to gas central heating boiler, plus the usual fridge-freezer type of thing.
Roof & Panels
I think my roof can take 10 x Perlight 425W on East facing and 11 x 425W on West facing side.
- East : 10 x 425W, or more likely two strings - one of 4 and one of 6 panels (rising winter sunlight reaches 4 panels earlier than the other 6 I think)
- West : 11 x 425W, or more likely two strings - one of 5 and one of 6 panels (some dappling through treelines after leaves fallen in autumn affects part of the roof surface)
Perlight 425W chosen as good wattage and efficiency and shape for my roofs, a bit higher Voc than some to see what's feasible. Panel specs are
Vmpp 34.6V
Voc 41.7V
Impp 12.30A
Isc 13.03A
ΔIsc/°C: 0.04 %
ΔVoc/°C: -0.27 %
- Possibly also 2 x 600W canadian solar panels or similar on a shed roof to boost winter PV, obscured by neighbouring rooflines except for about 3 hours in midwinter
I've used easy-PV to investigate different solutions to come to this point.
Battery
Think about 10-15kWh - so 3 x Pylon 5000 ? Probably aim to add more later
Options
Thoughts have narrowed down to a few main options
a) 5kVa Easysolar
b) Quattro 8k version, paired with a 450/200 (I don't think I need the generator input facility the quattro has, but the Multiplus 8k is not ENA certified in UK (yet))
c) Quattro 8k version, paired with 2 x 250/85 to give 6 x MPPT and allow panels on shed roof to also be used
Queries
Question 1a : Easysolar is not adequate ?
The 5kVA version of the EasySolar looks promising, but it may be a bit small for my situation.
- As the inbuilt 250/100 MPPT only has two inputs and doesn't take more than 5 of the perlights in series I think, so it pushes me down the route of 2parallel x 5series on both East and West sides ?
- Total is then 4250W on each roof, which is within the 9kW PV DC input limit for the kit.
- The DC power 4250W connected to the inverter is more than the rated AC output power of 4000W so it's 6% under-dimensioned for 20 panels, it can't take 21 panels, so I lose a panel and it's less efficient with respect to shading?
Question 1b : Are there any consequences of 2p5s into one MPPT vs 6 and 4 into two MPPTs ?
Question 1c : The 4kW A/C output limit may be wasteful or less than ideal?
a) I will have to export more to the grid as battery charging is limited to 4kW
b) seems 4kW is not ideal for a 7kW EV charger ?
Question 1d : Is there a bigger EasySolar ?
Question 2 : Which Quattro and MPPT set-up? Quattro 5k, 8k, 10k are approved by ENA, only Multiplus 3k and 5k though (as of March 2023)
Quattro option 1:
If I'm getting my head around it right then only using the main roofs:
- 8k Quattro with a 4xMPPT input of Victron SmartSolar RS MPPT 450/200.
- Panels configuration : 1x5, 1x6 on West and 1x4, 1x6 on East
- 3x US5000 Pylons .
Quattro UPS capability and the high continuous output power of 6400W, enough for the sunday roast, look tasty.
Question 2a : Is 450/200 a decent match to the panels ?
The 450/200 MPPT feels a bit like a goldilocks 1st and 2nd bear system for the #of panels. Each MPPT of the 450/200 can take 9 panels maximum I think.
Using maximum of 6 in a string feels like then the porridge is too cold - the 450/200 is over-specified, seems like MPPT capacity is wasted?
Using 11 panels in one string then the porridge is too hot - the 450/200 is under-specified as it can only take 9 panels?
If it was able to take 11 panels then I could go 1x11 and 1x10 on a single inverter and save some ££ albeit at expense of some potential shading issues, and have spare MPPT for the 600W shed panels, but can't do this
Question 2b is 6400W output not ideal for a 7kW EV charger ?
It also wouldn't be able to supply house (roasting sunday lunch) and charge EV at the same time in a worst case scenario? Hmmm a 10k Quattro can output 8000W continuous.
Quattro option 2:
If I'm getting my head around it right then ...
- 8k Quattro with a 6xMPPT input of 2 x Victron SmartSolar 250/85. with 4900W max PV input I think)
Panels configuration for Victron SmartSolar 250/85 #1 :-
1x5, 2x3 = 11 on West, or
1x5,1x3,1x3 = 11 on West
Panels configuration for 250/85 #2 (although may need a 250/100 with the 5800W max PV input):-
1x4, 2x3 =10 on East
1x2 from the south facing, but horizontally mounted, shed panels into the 3rd MPPT slot. Need to review the string voltages to be sure.
10*425 + 2*600 = 5450 kWp
Panel specs for CS 600W are
Vmpp 34.9V
Voc 41.3V
Impp 17.2A
Isc 18.47A
ΔIsc/°C: 0.05 %
ΔVoc/°C: -0.26 %
Question 3a
By having such small numbers of panels on each MPPT then there may be more occasions the start-up voltage is not reached and so less PV is actually available to be used ?
- This option is inefficient compared to the 450/200 ?
- Although it does enable the extra PV from the shed to be used in principle.
Question 4
Must confess I'm a bit confused by the myriad of Blue Solar, Smart solar, Tr, MC4, VE.Can variants. Are there any I should not use for domestic applications?
Question 5
Apart from some form of monitoring, are there any other 'blue boxes' needed to complete the kit?
Question 6.
I've seen the maximum PV input can be affected by the battery float voltage - an 8x limit on available PV voltage or something? And elsewhere a need for +5V over the battery voltage (iirc)
I have not seen this sort of thing mentioned on other manufacturers, e.g. something like growatt or givenergy. What's going on here ?
Thanks again.
