i've got 8 trojan (6v) T-125s not 105's. i think they're 240Ah each? in a 24V system gives me 480Ah.
i think i did the math on a 50% discharge (worst case situation) and found i could pull 3Kw from it without ill effects.
I find it much better to work in "watt-hours" of capacity. Takes all the system voltages out of the equation.
240AH * 6V = 1440 watt-hours per battery. Regardless of how you connect them - all series, all parallel, series-parallel, you have 8 of them @ 1440 watt-hours each = 11,520 watt-hours total.
At 50% depth of discharge (I think that's far too high, by the way) - you have 5760 watt-hours of "usable" capacity, or 5.76 kWh.
(Please note the extra 'h' in there. "3kw" is a meaningless figure in the context of battery capacity)