Assistance with solar calculations

DIY
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1

Greetings,

Needing some help with solar values for zipcode 72936 (Greenwood, AR)

For equipment I will be using an Epoch LiPo4 battery either 300ah or 460ah on a 12vdc system.

For the solar the plans are to run 2x 200w solar panels in parallel to receive more amperage for charging and also to help with shading (if it were to ever happen).

Solar panel specs:

Max Power at STC - 200W
Open Circuit Voltage - 36.5V
Short Circuit Current - 6.86A
Optimum Operating Voltage - 31.3V
Optimum Operating Current - 6.38A
Maximum System Voltage - 1000VDC
Maximum Series Fuse Rating - 15A
Module Efficiency - 20.7%

Per online calculators:

3.24 peak sun hours
29.3 degree of tilt
1 degree azimuth

All of this will produce annually 3.24 kWh/m2/day which is where I get stuck at.

I have a constant draw of 60w (converts into 5ah?) on this system. I need to ensure I have a minimum of 2.5+ days without sunlight protection which would equate to about the battery’s capacity based on those 60w.

For Victron equipment:

100/50 MPPT (unless I can go smaller)
CerboGX
Smart IP43 Charger (30a likely) for IF I hit that window or need the extra juice

Everything should be able to just be plugged into the Ethos battery and the BMS will take over since it has internal shunts and systems. I have spoken to them extensively about their product.

Can someone assist me with calculating and making sure that:

1: The 300ah battery or the 460ah battery is the better choice (specifying at 300ah how many days I can run without any sunlight) I am looking to bank positively into the battery during the day after the usage offset ie: If I am using 60w I want to be able to have a positive charge that by the end of the day I will have replenished the reserve.

2: Specify if 2x 400w panels in parallel is the way to go or do I need more panel?

3: Should the 100/50 MPPT be sufficient or do I need something different?

4: Would it be wise to wire this up so IF we transitioned to shore power the batteries were a reserve “backup only” or should we always pull from the batteries and let lets say a 30a charge controller just keep it topped off?

TIA !!! I am ready to build this thing if I can get the answers I need to not end up with buyers remorse due to bad calculations.

2

Looking at the solar available, it is half of what I get in Townsville, QLD, Australia, 2x 200W will not be enough. Your usage is 1.4kwh a day, and the production will be 1.3kwh a day.

You will be better with 2x 400W panels. You can stay with the 100/50, you might get clipped a few amps at peak production. I dont think you will miss it. It will be 10-15amps for 3-4 hours for a month or 2 a year. You could upgrade to the 150/70.

If you can afford the larger battery, get the 460Ah. You can never have too much solar and battery storage.

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