Hi there,
How fast you can charge a LA battery depends on the battery itself, the part number. It's often closely related to the capacity of the battery so bigger batteries can be charged with a higher current, but there is always a limit as to the max. You'll have to tell us what size your battery is or sizes of the two batteries if you have two, and any others that you plan to get. Generally it's not super fast for LA's, but to give you an example i have one that is 7.5Ahr and i can charge that at a maximum of 2.25 amps according to the manufacturer. I would not go above that limit. If i did charge at 2.25 amps, taking into account the charge acceptance of a lead acid battery i would have to charge it for about 5 hours, so that gives you some idea what to expect. It will probably take longer than that too as the voltage has to be limited also. I charge mine at 1 amp max though.
So long story short, i doubt you'll charge in less than 5 hours. That's the nature of sealed Lead Acid batteries.