Mixing Batteries on Float-- Mex Test Update 2

I'll note that there are a lot of RVers out there who have been and still are paralleling dissimilar battery banks for charging. Any motorhome with a b.i.r.d. (automatic battery interconnect) does this by default. I don't have numbers, I'll just say "a lot" of Fleetwood motorhomes are built this way. Whenever driving or plugged into shore power the coach and chassis batteries are connected in parallel with no time limit, in some cases for months at a time on shore power. When the charge current is removed, the parallel connection doesn't drop immediately, because the battery voltage has to go below a certain threshold to trigger the disconnect. From the factory my rig has a single FLA battery for the chassis and 2 FLA golf cart batteries for the coach. Some have replaced one or the other with an AGM battery. I've never heard of any problems or shortened battery life because of this system.