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Juraj Nikolov avatar image
Juraj Nikolov asked

Which panels used to pull out max. mppt 250/100 performance

Hi, I'm new here, I've been looking for discussions, but I haven't found what I'm looking for. I would like to ask what (and how many "serial and parallel con.") Are photovoltaic panels used to extract maximum power (5800wp at 0-F) from mppt 250/100 with 48V battery in the system? What are the ideal parameters for the panel: VOC, Vmpp, Isc, Impp or other necessary parameters. Another question is to connect the "easy solar 5VKA" to the grid, but I don't want (I can't have) to supply electricity from Victron to the grid, or I need to use a dual switch like some. "TOQ5-100PV / 4P"? I just can't send electricity to the grid but I can take it from the grid if I need it :)


Thanks for help.

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keithbrown avatar image keithbrown commented ·

There are many variables between you and your goal. Which 250/100? The TR or MC4? It's a little easier with the TR. If I recall correctly, both have an input DC amps limit of 70. for the MC4, you are limited to 30 amps per MC4 input too. How much parallelism do you need? What kind of shading issues? Keep in mind the fact that the cells are already paralleled and series'ed just to get the desired panel specifications. Your strings will be limited to 250v. That's VOC, not normal working voltage. SunPower 327w E20s have a VOC of 64.9. Strings of those panels are limited to 2 or 3. Do not exceed voltage or amperage of the charger. You CAN exceed total wattage.


I like SunPower and REC Alpha panels. The alphas are newer tech and will likely be more efficient but even old used SunPower panels put out a lot of watts. On the opposite end of the spectrum, BatteryHookup has some really strange 120w ENN panels for $1125 per 25. They are 141 volt thin film frameless glass panels. You could use a 150/100 charger if you haven't bought a charger yet. They cannot be combined into strings unless you have one of the new 450/100 or 450/200 chargers. At 1.32 amps, you could combine 50 of them in parallel for 6000w. They look great. Very tempting but I know nothing about their quality or real world efficiency. The wiring would get interesting. A roof of solid frameless black glass would be very appealing. each panel is 1300mmx1100mm. As they are glass with aluminum racking on the back, I could see adding heat strips to the racking to warm up the panels above freezing. I suspect you know you will destroy Li-ION or LIFEPO4 batteries at zero degrees F.

These are just a couple of examples. You really need to do your own research. This isn't like baking cookies.

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Juraj Nikolov avatar image Juraj Nikolov keithbrown commented ·

Hi,

I consider using EasySolar-II 48/5000 / 70-50A MPPT-250 / 100TR + GX, in the datasheet I state max. power converter 4400w (91A) but the converter has in its parameters is 70-50A (which is 3360-2400w) continuous output at 25C 4000w (83A) ... So I'm a little out of place here, as it is meant :) Multiplus 10kva plus necessary things instead of EasySolar-II 48/5000, it's just starting to grow in price :).

As for PV panels, I want to use 510w mono. panels Vmpp: 43.2 Impp: 11.81 Voc: 52.1 Isc: 12.42 Vtepm: -0.34 Itemp: 0.04. 6120wp, or add another mppt MPPT-250 / 100TR or MPPT-250 / 85TR or Ve.can if it were possible to combine and add another 8 or 12 panels, not any performance but if there is not enough sun. So I have a vision so far.

It would be absolutely ideal to use several mppt 100/20, which I would avoid with possible shadows falling on the panels, which should have an impact on better efficiency. The problem is that I did not find how to connect more than 4x mppt 100/20 reliably to one converter.

As for LIFEPO4, I do not plan to have the batteries located outside, but in a technical room where the temperature is 24-max40C. So they should be safe :) Thank you for your response.

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wkirby answered ·

There are many different types of PV panels you could use. Then whichever ones you decide to use they need to be connected in such a configuration to be compatible with your MPPT.

The choice of MPPT 250/100 and a 48V battery system gives you great flexibility.
The number one rule is to not exceed the 250V maximum string Voltage. This is the limit of the number of panels connected in series to keep under the 250V limit.
I'm not sure how cold 0°F is in real terms, but I think it is somewhere below the freezing point of water??? If so then you'd need to factor this in to your maximum series string Voltage. The Voltages written on the panels are usually for 25°C, and this Voltage increases as the panels get colder.

To maximise the output of the MPPT, you'd want it to produce the 100A charge current that it can provide. Size your array accordingly. If you have lots of sun then a 5KW array would be a good size.
If you don't have much sun then you could oversize the array to make more harvest in cloudy weather. The MPPT will safely limit to 100A even if the sun does come to visit occasionally.

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Juraj Nikolov avatar image Juraj Nikolov commented ·

Thank you for your response.

So if I understood correctly, I can use panels in such a setup?

Or which solution (connections) is better?

At this config is the PV voltage realy low, but Amps shud byt realy high. But it is cutted by mppt OK. Shud be usable this setup with this low voltage to charge batery and run the system in real life ?
1646240266329.pngOr better to use low PV power, but may it is more usable for the real system.

Thanks
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Juraj Nikolov avatar image Juraj Nikolov commented ·

This is the another setup. 1646242338248.png

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wkirby avatar image
wkirby answered ·

4 in series would be a better option to keep PV string Voltage high and less current in the PV circuit which means less loss in PV cables.
Then the MPPT will convert to low Voltage (48V) and high current to charge the battery.

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Juraj Nikolov avatar image Juraj Nikolov commented ·

Okay, I understand, so in series 4 in parallel 3.
May I ask if it is possible to connect an easysolar so that it can draw energy from the grid but not send it to the grid? From what I read in the manual, I either overlooked it or it's not there, but I read in the forums that it was possible. Can be done?

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kevgermany avatar image kevgermany ♦♦ Juraj Nikolov commented ·
By default, Easysolar only draws from grid. You have to have a GX device and configure it correctly to export. So no worries.
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