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PV Inverter recomendation

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donnib
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PV Inverter recomendation

Post by donnib »

Hi,
I have bought 20 panels like these (310w, 40V open, 10A) so in total there is 6.2kw PV array :
https://www.solartraders.com/uploads/pro...95gOJ3aeLA 310w model.

I have a house where i will be placing 10 panels on one side and 10 on the other (the house has about 45% inclination and it's not facing south, one part of roof pointing NW and one SE).
I am in process of making a diy LiFePo4 power wall made of 26650 cells and hope it comes up to 15kw). We have about 16-20kw usage in a day (2kids and 2adults). I live in a country where there are no inverters that are approved which can run with a DIY battery therefore i cannot register the system to feed to the grid. It must be a inverter that can pull from the grid in case not solar/power is enough. I was thinking somewhere around 5kw inverter.

What would you recommend ? I had a look at Victron but the price is extremely high even though it looks like great stuff.

/donnib

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weber
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Re: PV Inverter recomendation

Post by weber »

I suggest one or two of these inverters. And reflash them with our patched firmware.
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).

donnib
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Re: PV Inverter recomendation

Post by donnib »

Thank you for your reply. Since i have 20 panels and distributed on two sides that means i need two mppt chargers that can handle 160v, these support only 145v no ? How can i solve that problem ?

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jonescg
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Re: PV Inverter recomendation

Post by jonescg »

As long as the inverter has two MPPT inputs you can make that split array arrangement work.
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donnib
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Re: PV Inverter recomendation

Post by donnib »

But the 5048MS has only one MPPT no ? And the problem is still 160v > 145v.

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coulomb
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Re: PV Inverter recomendation

Post by coulomb »

donnib wrote:
Fri, 21 Feb 2020, 16:54
But the 5048MS has only one MPPT no ?
Yes. So you'll need an external MPPT as well as the internal one.
And the problem is still 160v > 145v.
You wire the panels in strings of 2S (72-cell or 144 half-cell) or 3S (60 cell). 5 strings of 2S wired to each MPPT would work.

There is a dual MPPT model, the PIP-5048MSD. But there is no patched firmware for it. So you would have to work around the premature float bug.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

donnib
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Re: PV Inverter recomendation

Post by donnib »

@coulomb Thank very much.

I realise the link to the panels doesn't work, here is another try where i attach it. Ok so i understand that i need another MPPT charger that runs to 10 panels (5 strings of 2s). Is 80V enough ? I mean is that not kind of low ?

What happens when i turn on a load that i connected to the AC out on the PIP when i also have another MPPT charger and i have full PV energy ? I guess the Inverter just pulls from the battery which both MPPT chargers are connected (both the internal and the external one), is that correct ? I mean is there any difference in having two inverters with their own MPPT charger compared to this where one is external in the essence that the energy that is produced right now from PV doesn't have to go to the batteries first ? Each string of 5p2s is 310w X 10 = 3100w and 5 x 10A = 50A i guess that's ok for one MPPT charger right ?

Three questions regarding the inverter :

1. Am i correct that this system will in no circumstances return power to the grid in case i can't consume it ? (i don't want it to since i am not allowed)
2. What happens if i have a load of 6kw and the inverter is 5kw so it will do bypass to grid ? What would happen to the energy from the battery and solar if available ?
3. What happens if i have a load of 2kw, my battery is dead but i have PV of 1kw. Will the inverter bypass to grid and at the same time charge my batteries and switch back when the sun energy is higher than load or battery can sustain the load ?

Yes i would like to avoid the premature float bug especially since i will be running LiFePo4.
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weber
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Re: PV Inverter recomendation

Post by weber »

donnib wrote:
Fri, 21 Feb 2020, 16:27
Thank you for your reply. Since i have 20 panels and distributed on two sides that means i need two mppt chargers that can handle 160v, these support only 145v no ? How can i solve that problem ?
You solve the 160 V versus 145 V problem by not connecting the panels in strings of 4. And yes strings of 2 would probably be too low in voltage. You should connect them in strings of 3. So you could either sell 2 or buy 1.

I suggested "one or two" of the Voltronic Power Axpert MKS 5K inverters. If you bought two you would have two MPPTs, and 10 kW AC output capability (with the addition of 2 paralleling kits).

But you don't actually need two MPPTs. You can connect NW strings in parallel with SE strings, without requiring blocking diodes. Shaded strings are cooler, and so their voltage is higher, which prevents them from taking any significant current in reverse from unshaded strings. The essential thing is that panels in the same string must face the same direction. Of course you will extract more energy with two MPPTs.

There is nothing stopping you connecting 18 panels (as 6 strings of 3), i.e. 5.58 kW, all to the PV input of one inverter. The inverter's MPPT will never draw more than 4 kW from the PV array, so you will miss out on some energy in the middle of sunny days. But you probably don't need it then anyway, and will not be able to store it as the battery will be full.

Two of these inverters is better than an inverter plus a separate Voltronic MPPT because we do not have patched firmware for the separate MPPTs, to fix the premature float bug or to suit LFP cells.
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).

donnib
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Re: PV Inverter recomendation

Post by donnib »

So you could either sell 2 or buy 1.
If i have 20 now and i place 10 on each side then i would need to buy 4 panels more to make strings of 3 no ?
You can connect NW strings in parallel with SE strings
Yes i have heard but many told me i will lose quite much doing this but if i can get away cheap by just getting a MPPT controller. What i don't know is if there are any downsides of one separete MPPT charge controller versus another inverter with charge controller inside ?
The essential thing is that panels in the same string must face the same direction. Of course you will extract more energy with two MPPTs
Yes i know this is important.

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Re: PV Inverter recomendation

Post by weber »

donnib wrote:
Fri, 21 Feb 2020, 22:28
weber wrote:So you could either sell 2 or buy 1.
If i have 20 now and i place 10 on each side then i would need to buy 4 panels more to make strings of 3 no ?
If you sold 2 you could have 9 on each side. If you buy 1, you could have 9 on one side and 12 on the other. Assuming you're in the northern hemisphere, the 12 should be on the SE side, if they will fit.

Sure you could buy 4 more and have 12 each side, but you should not do this if you will only have one inverter (and hence one MPPT).
You can connect NW strings in parallel with SE strings
Yes i have heard but many told me i will lose quite much doing this but if i can get away cheap by just getting a MPPT controller. What i don't know is if there are any downsides of one separete MPPT charge controller versus another inverter with charge controller inside ?
I foresaw this question and have already answered it above, but I did it as an edit after my initial submission, and apparently I was not quick enough, as you were already responding.
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).

donnib
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Re: PV Inverter recomendation

Post by donnib »

Ok i understand what you meant about the PV quantity.

I was thinking it would be nicer with same quantity on each side but you are right, it doesn't have to.

And yes i was sort of guessing about the premature float bug only being solved on the inverter.

Here is the house with a compass so you can see how the direction of the roof is :
house.png
house.png (504.81 KiB) Viewed 627 times
Hmm...so i have few options if i don't want to sell panels :

1. Get 4 more and have 4p3s meaning 40A and 120V on each side of the roof
2. Get 1 more and as you said on one side 9panels meaning 3p3s 30A 120V and on the other side 12panels meaning 4p3s as above.

Then i have two options regarding the inverters:

1. Get one inverter and connect both sides to the same MPPT charger and loose everything above 4kw meaning 2,5kw which quite much.
2. Get two inverters and then connect each side to one inverter and gain 10kw.

In case of two can the two handle 10kw load in bypass ?
Isn't there a 4048MS model that is cheaper ?

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Re: PV Inverter recomendation

Post by weber »

donnib wrote:
Fri, 21 Feb 2020, 23:12
And yes i was sort of guessing about the premature float bug only being solved on the inverter.
You could use a separate MPPT that is not made by Voltronic, and so does not have the premature float bug, and that lets you set the lower voltage threshold for going from float to bulk/absorb to suit an LFP battery. I expect that's what Coulomb had in mind.
1. Get one inverter and connect both sides to the same MPPT charger and loose everything above 4kw meaning 2,5kw which quite much.
I do not recommend connecting more than 18 of those panels to one PIP-5048MS inverter. That's 40% oversupply.
In case of two can the two handle 10kw load in bypass ?
Yes.
Isn't there a 4048MS model that is cheaper ?
No. It is no longer available.
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).

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Re: PV Inverter recomendation

Post by coulomb »

weber wrote:
Sat, 22 Feb 2020, 15:51
Isn't there a 4048MS model that is cheaper ?
No. It is no longer available.
Well, I'm sure that there are still some for sale somewhere on the planet, but they're likely to have been in a warehouse for years, possibly a hot warehouse, so the capacitors may have already dried out significantly, leaving questions about the expected life of the unit. As far as I know, they have not been manufactured since the first half of 2017.
Nissan Leaf 2012 with new battery May 2019.
5650 W solar, 2xPIP-4048MS inverters, 16 kWh battery.
1.4 kW solar with 1.2 kW Latronics inverter and FIT.
160 W solar, 2.5 kWh 24 V battery for lights.
Patching PIP-4048/5048 inverter-chargers.

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weber
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Re: PV Inverter recomendation

Post by weber »

donnib wrote:
Fri, 21 Feb 2020, 21:03
What happens when i turn on a load that i connected to the AC out on the PIP when i also have another MPPT charger and i have full PV energy ? I guess the Inverter just pulls from the battery which both MPPT chargers are connected (both the internal and the external one), is that correct ?
Yes.
I mean is there any difference in having two inverters with their own MPPT charger compared to this where one is external in the essence that the energy that is produced right now from PV doesn't have to go to the batteries first ?
There is no difference, in that sense.
1. Am i correct that this system will in no circumstances return power to the grid in case i can't consume it ? (i don't want it to since i am not allowed)
Correct.
2. What happens if i have a load of 6kw and the inverter is 5kw so it will do bypass to grid ?
Yes.
What would happen to the energy from the battery and solar if available ?
When bypassing, it can still charge the battery from the solar, and it can charge the battery from the grid if you allow it. There are various conditions you can apply. But it cannot combine grid power and battery power to feed the loads.
3. What happens if i have a load of 2kw, my battery is dead but i have PV of 1kw. Will the inverter bypass to grid and at the same time charge my batteries and switch back when the sun energy is higher than load or battery can sustain the load ?
Yes, you can set it up to do those things.
One of the fathers of MeXy the electric MX-5, along with Coulomb and Newton (Jeff Owen).

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