[zeuspaul]

I do the math a little differently. I prefer watts because a 104 watt pump is 104 watts no matter the source voltage. For example your 104 watt pump draws .9 amps from 120 volts but it draws about 8.7 amps from a 12 volt battery.

Drawing a lead acid battery all the way down can significantly reduce the life. 50% is the sweet spot for deep cycle and I would not go below 80% on a regular basis. Designing for 50% your 100 amp-hr battery holds 600 watt-hrs (100x12/2)of useable juice. A 104 watt pump would run for about five hours(600/104). Two 104 watt pumps would run 150 minutes. That works out to a little over six days at 24 minutes per day.

I would plan on charging once a week for a deep cycle battery. If using an automotive starting battery charge twice a week.

The calcs are about the same for 104 watt DC. DC pumps may cost a little more and you may have to change brushes. However you save the cost of an inverter.

You may have trouble with your existing inverter with two AC pumps when you consider pump starting surge.