Batteries hook together should be of the same size and type. If you have a 3 stage charging system it will not be able to determin the battery state because it will have to average the condition of each battery. If you have the original univolt it will be cooking the 30 amp long before the 100 ah is fully charged. I would run with the 100 ah and leave the 30 at home. Memorial Day weekend I went 4 days with my Lifeline AGM and the battery still showed "good". I can extend my days off the grid by topping off the battery with my Honda EU1000 generator. It's small, light and very quiet.
WBCCI President 2016-2017