What are your expectations from your batteries? With my 2 8-D house batteries, my coach will drop to 11.7 volts overnight WITHOUT the stand alone ice maker running. With it running, I will drop to 11.7 volts in 4-5 hours. More batteries are installed on the all-electric coaches (4-6). To get more charge, several issues are in play. 1) Any battery you use for the house batteries should be a deep cycle battery rather than a starting battery. A starting battery will kick out a large current for a short period of time while a deep cycle battery is designed for providing a lower current flow for an extended period of time. Golf cart and deep cycle batteries are a requirement for house batteries as a starting battery will not recover from being pulled down to a low state of charge very often. I do use AGM batteries on my house batteries and they have served me well for almost 7 years. 2) I keep my batteries on a charger most of the time but have pulled them down significantly when using the inverter for extended periods with the stand alone ice maker running. If your coach is not plugged in, make sure you always turn off the main coach battery shut off to keep from bringing the batteries down to such a low state of charge that they are damaged. If it is plugged in, make sure your battery charger is working properly. 3) Make sure that the charger is set for the proper type of battery as different types of batteries (wet cell, agm, gel) require different charge rates. The old battery boilers that were installed many years ago are hard on batteries. Most modern inverter/chargers or new stand alone chargers are multi-stage while will extend the life of the batteries. I disconnected the old battery boiler (stand alone battery charger) in my coach and installed a pure sine wave inverter/multi stage charger unit.
Generally, AGM's do self discharge slower than Wet Cells, however we are talking months here, not days.
If by "holding a charge" you mean that when boondocking you have to charge 'em every day.. That is normal and changing to AGM's will only flatten your wallet. VERY FAST
Now if were talking about parking for months at a time I think that is where AGM's would be better (Provided you disconnect negative cables from the batteries before parking, or right after (As in a few minutes)
SOME AGM batteries are kind of interesting, Lifeline specifies a re-charge rate of 30 to 300 percent capacity. Most battery makers say "No faster than 30% and Trojan, says even slower (like 10%) You don't need to water AGM's. you rarely need to equalize.
But as for providing amp hours of power (Watt hours if you like) running your furnace, inverter, and such.. No advantage at all.. Flooded wet cells give the best bang for your buck
My 2 8D house batteries with a small freezer (instead of icemaker) running + a few other things running, fan, etc. will still be above 12V in the morning. Enough to run the coffee pot. They are AGMs with PowerPulses.
My coach has six 8D house batteries which are basically starter batteries. When they go bad, my plan is to replace them with 12 deep cycle golf cart batteries. To keep them watered and to avoid gassing, there are single point watering systems available which makes it easy to maintain water levels and avoids gassing.
2001 Newell #579
tow a 2011 Honda Odyssey
1935 Mercedes 500K replica