I have six lithium batteries (105Ah each) in parallel that I am configuring on a Sunsynk inverter. What battery capacity should I configure here? Is it the sum of the six batteries or I juts put in the 105Ah??
In parallel the voltage stays the same and the Ah is added together. In series, the Ah stays the same, and the voltage is added together.
So you have a 12V 600Ah battery when placed in parallel.
An easy way to remember this is that 1) Volts times amps = watts, therefore 2) volts times amp-hours = watt-hours (Wh), and since you cannot make energy out of thin air, the total energy must be the same for series or parallel.
And indeed: 6 * 12 (72V) times 100Ah is 7.2kWh, and so is 12V times 600Ah 
Edit: And yes, I know I rounded 105 to 100. It is close enough. That extra 5 is mostly marketing.
I did not know Sunsync comes out in 12v? Google tells me naught. Did I miss it?
Hi Rufas
When you say 105Ah, do you mean 12v batteries or 48v batteries.
If it’s 48v, then that’s a big bank and parallel is fine.
If it’s 12v, then you can’t connect 6 batteries in series or parallel as the sunsynk is a 48v battery.