lifepo4 8s 280Ar series or parallel?

It does not matter in detail... Both 12v @ 560 AH and 24v @ 280 AH store the same amount of energy:

• Power = Voltage * Current
• Power = Voltage * Current * Hours (Time)
• 12 volts * 560 AH = 6,720 Watt*Hours
• 24 volts * 280 AH = 6,720 Watt*Hours

The 12 volt bank will have to supply 2x more current for the same amount of power:

• Power = Voltage * Current
• Current = Power / Current
• 200 Watts / 12 volts = 16.7 Amps
• 200 Watts / 24 volts =  8.3 Amps

So, for the "same amount" of power, you will need 2x heavier wire and 1/2 the length (to keep voltage drop reasonable)--More or less.

If you need 12 VDC power for your devices--12 VDC is fine. If you don't need 24 volts, and are looking at using AC inverter--24 volts (or even 48 volts for a larger battery bank) is usually a better choice (smaller wire, longer distances @ 24 VDC, using a solar charge controller--Both may be rated at 50 amps--But 24 VDC battery bus will "manage" a 2x larger array vs a 12 battery bus)

• 14.5 volts charging * 50 amps = 725 Watt array
• 29.0 volts charging * 50 amps = 1,450 Watt array

Note it may be "more difficult" to find inexpensive BMS for 48 volt systems....

Do paper designs for your system--12 and 24 volt based on your loads and see what the issues are.

Give us you Load Needs, length of wire runs, and Solar/other charging sources--And we can walk you through the process.

-Bill