Battery drain calculation?

[cdig]

I'm trying to figure out if I can circulate water in my horse waterer on a 12v deep cycle battery...

My numbers are:

12v pump that draws 1.9amps (12 x 1.9 = 22.8watts)
22.8w /1000 = .0228kW
.0228 x 24hours = .5472kWh ??


So given the above numbers, I'm hoping someone knows how to calculate just how long a 12v battery will last with a .0228kW drain on it? If I have say a 800cranking amp deep cycle battery?

Thanks,

C.