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Moonshine82

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I have 7 310w panels08A2D5DD-CC72-4618-ADC2-C8FC2BF6883D.png and looking to go with 2

4PCS VariCore 3.2V 280Ah lifepo4 battery DIY 12V 280AH​

what inverter and mppt or general set up would you guys recommend? Need to do my maths in my total loads but ballpark I’m powering a 37x18 cabin with chest freezer, fridge , 10 lights led, charging phones x2 washer and dryer but dryer is off propane, vitamix, baby monitor and would like a small bit of wiggle room would love some tips on series parallel config was well
 
You do not specify whether this is grid tie or off grid application. I will assume off grid.

Lets look at the possibilities of your array. With 7 panels, using all 7 is unlikely because its an odd number unless all series or all parallel array works out for your SCC.

7 x 310w = 2170w
2170w / 12.8v battery = 169.5 max charging amps (this is a LOT but with low sun angle, solar harvest much less).

All series: 7 x 40.3 = 282.1v (this would require a rare and expensive SCC so i will not recommend this)
All parallel: 7 x 9.3A = 65.1A (this would require significant wiring from array to SCC so if this is a long run then it would not be very practical)

2 series, 3 parallel: 80.6v 27.7A (will work with smaller 100A SCC but getting high charge amps limited)
3 series, 2 parallel: 120.9v, 18.8A (very reasonable to me)

Pursuing 3S2P array, a Victron 150/85 would get you 85A of charging which is quite a bit for your battery.
This is what I would recommend to my friends.

And yea, you'll have one panel extra. You are pretty much over paneled for your battery unless you have low sun angles (far north or south) and hope to harvest all you can get. Then this is a good match.

I cannot tell how much power your appliances you listed above use but if you maximize their use during the peak solar hours of the day that would help quite a bit.

Others hopefully will chime in with higher amp battery charging SCC's. You will have the solar to support quite a bit more.

Hope this helps.
 
One more idea:
Instead of one huge SCC and an unused panel, you can setup 2 smaller systems to spread the solar harvesting across the day. If you have 3 panels (all in series) east-ish with a Victron 150/50 and 4 panels (2 series, 2 parallel) facing west-isn with a matching Victron 150/50 you would use all 7 panels and start charging earlier and finish charging later.
Obviously you could have 4 panels east and 3 panels west... not sure how i'd determine which to do. Maybe 4 east if i expected to deplete power at night and wanted/needed power earlier in the day. Conversely, having 4 west you could maximize late afternoon charging to ensure power at night.

Make sense?
 
MisterSandals said:
One more idea:
Instead of one huge SCC and an unused panel, you can setup 2 smaller systems to spread the solar harvesting across the day. If you have 3 panels (all in series) east-ish with a Victron 150/50 and 4 panels (2 series, 2 parallel) facing west-isn with a matching Victron 150/50 you would use all 7 panels and start charging earlier and finish charging later.
Obviously you could have 4 panels east and 3 panels west... not sure how i'd determine which to do. Maybe 4 east if i expected to deplete power at night and wanted/needed power earlier in the day. Conversely, having 4 west you could maximize late afternoon charging to ensure power at night.

Make sense?
Click to expand...
Best advice so far , and yes off grid application was thinking to go 24v, I can also get another panel and increase to 8 or go with a diff/more battery set up but just seemed those batts I posted where lots of ah for the price seemed worth it. I just don’t want to get to big of a inverter ( any recommends?)and create a waste draw and mppt ratings kinda confuse me on the converters
 
Last edited:
Moonshine82 said:
yes off grid application 24v
Click to expand...
You will need 8 LiFePO4 cells in series to make 24v. (3.2v x 8 = 25.6v aka 24v battery)

So using the same 7 panels as above:
7 x 310w = 2170w
2170w / 25.6v battery = 84.7 max charging amps (still a LOT).

Moonshine82 said:
I just don’t want to get to big of a inverter and create a waste draw and mppt ratings kinda confuse me on the converters
Click to expand...
The SCC does not have a draw and its not the same thing as an inverter. An inverter, converts your battery power (25.6v DC) to household current (120v AC) ... there is a standby draw on these inverters but they can always be turned off when not needed. Thats a different battery "use" discussion (we're talking charging here!).

The MPPT specs involve 2 main items: input voltage and charging amps.
All SCC's have a max input voltage (the voltage from the solar array) that in important to never exceed (bad!).
The charging amps are the watts of your array divided by the voltage of your battery (and limited by the amperage of your MPPT SCC).
Your max available amps from your array to your battery, in theory is 84.7 (see a dozen lines above).

An 40A MPPT SCC will only ever charge your battery at 40A as that is what it was made to do.
An 80A MPPT SCC will only charge your battery at 80A (even though your array "could" produce 84.7A).

Questions?
 
Man you are a wealth of info Thank you, ok so I’ll be looking at 100/80 mppt unless I add a panel or go with the absolute genius idea of a split system correct? And then I. Need an inverter recommendation I know I don’t have an exact number on my loads but was thinking 2000w or if I add a panel I go 3000w ballpark
 
Moonshine82 said:
Thank you, ok so I’ll be looking at 100/80 mppt unless I add a panel or go with the absolute genius idea of a split system correct?
Click to expand...
If you got an 8th panel, you could make 2 smaller and identical systems (fewer spares!).

With 4 panels east-ish and 4 west-ish: with 2 in series and those in parallel (2S2P), your panel Voc 40.3 x 2 is low enough for you to get 2 very reasonably priced and top notch Victron 100/50 (takes up to 100v input and charges at a max of 50a).

Victron 100/50:

The numbers for the panels and this SCC match up nearly perfectly. I'd recommend this to my mom.

So you would have 2 arrays of 4 panels each:
4 x 310w = 1240w
1240w / 25.6v = 48.4a (theoretical max in a 100% efficient world)

This would provide some redundancy so if one piece failed you'd still have half running. And keeping a spare for 2 identical systems is feasible.
 
Last edited:
Moonshine82 said:
Need an inverter recommendation I know I don’t have an exact number on my loads but was thinking 2000w or if I add a panel I go 3000w ballpark
Click to expand...
So this is a completely different exercise. Do you know how much power you use in a day?
How much of that comes from AC (household current) appliances?
Its the inverter that is sized for your AC appliances.

All your DC items will run directly off the battery at 24v (like maybe a refrigerator) or will be converted to 12v for standard 12v items (as are in most RV's and cars).

Here is a tool to help you figure out how much energy you use so we can size your inverter correctly:
System Energy Audit and Sizing Spread Sheet

There is also a guide for selecting system voltages but it can be roughly summarized as:
If you need an inverter 3000w or bigger, then use a 24v battery bank. Smaller than that will work with a 12v battery bank.

If you get stuck with the spreadsheet or need help, please ask. Its critical to get as close as possible with your energy needs.
 
Wow great spreadsheet thx will def use before buying inverter ; Love your idea of the 2 smaller systems will prob be doing that. recommend still doing 24v batt bank? Can both systems go from their scc to change the same bank? Or do they need their own batt banks
 
Moonshine82 said:
recommend still doing 24v batt bank? Can both systems go from their scc to change the same bank? Or do they need their own batt banks
Click to expand...
Lets see what your max AC loads will be to determine how many watts your need to pull at any time.

And yes, multiple SCC's can work together without problem. Its fairly common to have multiple chargers hooked to the same battery bank.
 
MisterSandals said:
If you got an 8th panel, you could make 2 smaller and identical systems (fewer spares!).

With 4 panels east-ish and 4 west-ish: with 2 in series and those in parallel (2S2P), your panel Voc 40.3 x 2 is low enough for you to get 2 very reasonably priced and top notch Victron 100/50 (takes up to 100v input and charges at a max of 50a).

Victron 100/50:

The numbers for the panels and this SCC match up nearly perfectly. I'd recommend this to my mom.

So you would have 2 arrays of 4 panels each:
4 x 310w = 1240w
1240w / 25.6v = 48.4a (theoretical max in a 100% efficient world)

This would provide some redundancy so if one piece failed you'd still have half running. And keeping a spare for 2 identical systems is feasible.
Click to expand...
Would you by chance have a diagram of this set up?
 
Moonshine82 said:
Would you by chance have a diagram of this set up?
Click to expand...
Here is 1 of the 2S2P arrays. Note there are 2 panels in series, twice. The top left panel's "+" wire is connected to the bottom left's "-" wire to make the series connection. Same with the top right and bottom right panels.
Those 2 strings are combined in parallel by connecting the "+" wires from each string together and also connecting the "-" wires together to make the parallel connection. Thus 2 in series, then 2 in parallel (2S2P).

The series connections add the volts for the panels: 40.3v + 40.3v = 80.6v, the amps remain the same.
The parallel connections add the amps for the series strings: 9.3a + 9.3a = 18a.
Total array: 1240w 80.6v 18a
Create 2 arrays like this with one pointing east-ish and one pointing west-ish.
Not shown are each SCC connecting to the battery bank.

Screen Shot 2021-01-11 at 10.05.37 AM.png
 
I swear you are the most helpful info I have found I am really grateful for your knowledge and patience thank you for all that you do
 
MisterSandals said:
Here is 1 of the 2S2P arrays. Note there are 2 panels in series, twice. The top left panel's "+" wire is connected to the bottom left's "-" wire to make the series connection. Same with the top right and bottom right panels.
Those 2 strings are combined in parallel by connecting the "+" wires from each string together and also connecting the "-" wires together to make the parallel connection. Thus 2 in series, then 2 in parallel (2S2P).

The series connections add the volts for the panels: 40.3v + 40.3v = 80.6v, the amps remain the same.
The parallel connections add the amps for the series strings: 9.3a + 9.3a = 18a.
Total array: 1240w 80.6v 18a
Create 2 arrays like this with one pointing east-ish and one pointing west-ish.
Not shown are each SCC connecting to the battery bank.

View attachment 32806
Click to expand...
With this config 10awg should be ok for all my panel wiring correct?
 
Hey mister sandals finally got my battery bank order in been waiting on their stock to replenish I am going with 6 SOK Battery 100Ah 12V LiFePO4 Deep Cycle Battery | Lithium Solar Batteries, I know we where chatting about a split system but I found an all in one mppt/inverter that I wanted to run by you to see your thoughts. The growatt 3000TL 24P, of course I still don’t know my exact loads haven’t bought appliances yet but estimating for a 700sq ft home I’m guessing this will be enough, large appliances will be on propane, water heater is propane heating will be comming from wood so just lighting and small appliances off my system in theory
 
Looking for help on sourcing an ac distribution panel as well looking to do about 12 ac outlets inside home any info would be great don’t even know where to start with that
 
Moonshine82 said:
The growatt 3000TL 24P
Click to expand...
I am unfamiliar with this unit but there are many threads about it (use search tool).

Knowing you AC loads will be key to this being suitable. I prefer distinct SCC and inverter because i have 2 distinct systems that i move equipment between. And if one piece fails, it does not take down multiple functions.
 
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