I have read many myths about batteries over the years.
Now.. Charging ASAP when you buy a new battery.. Very good plan
BUT... can you just put 'em in in parallel with others that are already charged and let the converter do it's job?
The myth is the "Full" batteries will tell the converter they are full and the new one will never get fully charged.
Another like myth is if you group say a Group 27,29,31 that the 27 will fill up and the 31 will never.
This is based on the theory that all 3 of those (in the example) share amps EQUALLY during charging.. they do not.
THe battery with the lowest voltage takes the lion's when you add a battery
And once that is done they share both charge and load ACCORDING TO THEIR ABILITY. not equally. for example my GC-2's take over twice teh current and provide over twice the current of the G-29.