This C&D Technologies easy-to-read-and-understand technical paper is my "bible" in how to charge VRLA (AGM) batteries. Notice that they mention/imply/show-on-graphs throughout the document that recharging of VRLA batteries using 13.8 volts as just another voltage choice one can make for recharging - based on various conditions, parameters, and available recharge times. I can't seem to find anywhere in the paper where it states the one "must use" 14.X volts for AGM recharging in order to keep your AGM batteries from being slowly ruined. The paper of course makes the point throughout that AGM batteries must often as possible be fully recharged to keep from harming them in the long run. (C&D Technologies manufactured my first set of twin 12V 100 AH AGM RV batteries.)
Here's the easy to read technical paper I'm referring to above:
http://www.cdtechno.com/pdf/ref/41_2128_0212.pdfHere's a list of links to a whole bunch of other excellent C&D Technologies publications dealing with VRLA (AGM) batteries:
http://www.cdtechno.com/resource/support_doc.html
