Checking the math on 1.65 kwatt off grid solar system

[sailor4life7777]

Hi guys, I'm about to purchase the components for my off grid solar system but I wanted to check my math with all you amazing people first! I plan to buy 3 550 watt solar panels (Vmp=41.96, Voc=49.90, A=13.11) and wire them in series. I plan to buy a 24V, 100AH lithium ion phosphate battery. I plan to buy a 100 amp MPPT solar charge controller (1650watts/24V *1.25=86) and a 3000 watt inverter. Am I making any mistakes anywhere?

Thanks in advance guys!

[Ratel]

Try this handy calculator:

https://www.explorist.life/solar-cha...er-calculator/

[smac999]

A single 100ah battery sounds very small for the panel and inverter size. Unless you plan to only use power when it’s sunny.

Make sure the controller can Handle 150v. That is pretty high.

[sailor4life7777]

Thanks for the replies guys! So I can't seem to find any 100 amp charge controllers that can handle 150V on aliexpress, the max I can find is 50V. Does that mean I will need to wire my panels in parallel then? Not a big deal, but are there any other ways I can still wire my panels in series if the solar charge controller can only handle 50V max? How difficult is it to source solar charge controllers that can handle 150V, 100amps?

Thanks again to everyone!!!

[steve77]

I assume this is for a land-based permanent Installation. If so, there are controllers readily available that will easily handle your three 550 Watt panels in series. For one, look at the Midnite Solar Classic. There are others, but this is a place to start.

Cheers!

Steve

[jhilley]

Look at Victron

[valhalla360]

First question: How much power do you need? Both peak wattage draw and total KWH?

But looking at the info provided:

Nominal rating: 1650w (3 @ 550w)
At 24v = 69amps
100amp @ 24v charge controller should be OK.
Daily output around 6.6kwh (assumes 4 times the rated wattage in w-hr)
100ah battery at 24v = 2.4kwh

Are you planning to use the bulk of the power (maybe 2/3) as it's produced during the day?

If not, your battery appears to be undersized and much of the solar generation will go to waste.

Also, are you on or off grid? If off grid, you should consider how many days you want to operate if solar output is down due to overcast conditions. (if on grid, the grid will pick up the slack during overcast days).

[redneckrob]

Originally Posted by sailor4life7777

Thanks for the replies guys! So I can't seem to find any 100 amp charge controllers that can handle 150V on aliexpress, the max I can find is 50V. Does that mean I will need to wire my panels in parallel then? Not a big deal, but are there any other ways I can still wire my panels in series if the solar charge controller can only handle 50V max? How difficult is it to source solar charge controllers that can handle 150V, 100amps?

Thanks again to everyone!!!

There are few benefits to wiring in series and lots of benefits of wiring in parallel, which leads to much less impact from partial shading. Did you have a reason for wiring the panels in series?

[donradcliffe]

Look at maximum discharge current for your battery BMS. If its 100 amps at 24 volts, thats about 2500 watts, and your inverter could trip the BMS. I agree that the battery is undersized for the solar array, and rwo 100 amphour 24 voltt batteries in parallel would solve both those issues.

[mitiempo]

Originally Posted by redneckrob

There are few benefits to wiring in series......

In an off-grid situation with the panels placed to avoid shading there is no disadvantage to wiring in series. Smaller wiring needed for what could easily be a long run.

I agree with others - the battery is too small. I doubt it will sustain a 3000 watt inverter for very long before shutting down.

I would look at Victron controllers.

[jmschmidt]

I think (hope) you mean lithium IRON phosphate, not lithium-ion phosphate. I have three of the 1,000AH lithium-iron type in my home storage system powered by a twelve-panel solar array. Works great in conjunction with my 36-panel grid-tied standard system which gets a one-for-one credit for power it produces. The two together wipe out all my electric bills for the year.

The lithium-ion phosphate batteries have already caught fire on several of the high-brid tugboats. They had to be replaced by lead-acid batteries.

[sailor4life7777]

Hi guys, thank you very much for all the replies! I am oversizing my solar panel array on purpose, so it's more that the solar panel array is oversized than the battery is undersized. I really only need a 1kw inverter, but I figure I will buy the 3kw inverter in case I do decide to buy another battery. I read that there's really no downside (other than money) to using a bigger inverter and since I won't be using much load on the inverter, it shouldn't trip up the battery/bms correct?

I want to wire in series to get as much power generation/battery charging on cloudy days and during early morning/dusk as possible. I dont expect to have any shading. What other benefits does parallel wiring offer other than protection against shading? (and being able to use a smaller 50V charge controller!)

Thanks again to everyone for all the great input!

And yes, lithium iron phosphate, mymistake...

[mitiempo]

Which battery are you buying?

As long as there is no shading and the controller can handle the voltages series has no advantages over parallel.

[sailor4life7777]

Originally Posted by mitiempo

Which battery are you buying?

As long as there is no shading and the controller can handle the voltages series has no advantages over parallel.

This battery: https://www.aliexpress.com/item/4000...65422794%21sea

Do you mean to say "As long as there is no shading and the controller can handle the voltages, parallel has no advantage over series?", not the other way around? Series only downside is from shading and from requiring a charge controller that can handle large voltages, correct??

Thanks again to everyone for all the replies!

[waterman46]

How long is the wire run? Wire in parallel and wirh 3 controllers you have no issue with fatal shock, 3 x reliability. And 2 or 3 of those 24V batteries will allow you to use that inverter on a cloudy day or two.