Definitive Answer
I have in front of me that manual for the HeartInverter /Charger, and here's some of the excerpts.1. pg. 13 AGM Batteries. "This battery is lead acid but maintenence free. They hold the liquid electrolyte in a sponge like material. The performance is similar to gel cell batteries. The charge parameters are similar to wet cell batteries." 2 . pg. 9 . Describes the different settings available for charging modes. They are Wet, Gel 1, gel 2, AGM. Gel 1 or 2 depends on what rate of charge you want. Gel 1 for longer battery life, rate 2 for rapid charging. The difference between wet and AGM is given in a table on pg. 20.The float and accept voltage is .1-.2 volts lower on the AGM. 3. pg 16. "AGM and Gel cell batteries must not be charged to their gassing point. In fact, high voltage charging which gasses these batteries is harmful to them. They typically require a lower bulk charge voltage. Gel cell batteries require a higher float charge voltage than wet cell batteries." Maybe this is what explains the voltage difference in item 2.