FWIW just as a point of reference in the weight department: The 12V Group 31 deep cycle AGM batteries we are using in our RV weigh in at about 12 lbs. per cell - a little over 72 lbs. per battery. I've only seen one heavier ... the Group 31 Lifeline 12V deep cycle battery at ~75 lbs. per battery.
This is the battery we're using a couple of:
http://www.fullriverbattery.com/product/batteries/DC115-12I think our battery model is also getting rebadged and supplied to these guys as this battery model:
http://www.rollsbattery.com/wp-content/uploads/batteries/S12-128AGM.pdf