Phil has suggested that maybe all AGMs can be hit with really high charging rates despite having max amps in their specs. ISTR Mex has hinted that.
Meanwhile, some AGMs do have minimum charging rates in their specs- same 20% mentioned for several. But some like my two different brands of AGM have no mention of a minimum charging rate, but they do have max rates specified.
Mex says to ignore that and treat them as though they do have a 20% minimum.
I find that 20% business to be a huge PITA, but I don't dare ignore Mex if I want to keep my AGMs healthy. I don't need to try a higher charging rate than specified, so that is no problem.
What is the truth then? Are all these deep cycle AGMs about the same, despite their different charging specifications, or not?