Marine/RV 27s (flooded) like low and slow best of all to get them properly full. But you must keep the charge going as the battery voltage rises to 16v before stopping. At that point, the SG will be well up where it belongs. Now you can go to your float voltage.
I do that with my VEC1093 at the 4 amp setting and with the Equalize button pushed, so it keeps going all the way up to 15.7v at low amps. I used to try fast charging with them, but the SG never came up properly.
BUT--AGMs are the opposite. They want fast charging or no go. Mex says that is to get the chemistry to happen right.
You can't do the low and slow to 16v with the usual converter or charger. No amps level setting, so can't keep them low and voltage limit is in the 14s, so can't get to 16v.
You can't do AGMs right either unless you can run a big enough amps charger (to do the 20% rate) with your 120v supply. With many, you can't keep it from dropping to 13.6 volts before the amps have tapered down to 0.5a per 100AH. I do that with my adjustable voltage PowerMax so it stays at 14.x until I say so.
So you are basically up a tree as an RVer unless you do after-market equipment buying and are willing and have the time to do it right. I figure most folks don't have the time or situation to baby their batteries. (trailer kept in storage lot with no 120v available because not allowed to keep it in your sub-division in your yard, eg)
Or you just live with it and buy batteries as part of the price to be an RVer. Luckily batteries are not very expensive on a three-year basis.
