converter charger

[ollygogs]

i have an american rv and the converter charger is over charging so im told by my auto elec guy. Its a 240v and 40amp the rv is 240 or 12v of two leisure batters can i change it for a good normal high amp battery charger been offered a ring RCB320 at a very good price which is a 20amp charger with an 80 amp boost or do i have to have a proper motor home converter charger many thanks for your help