I'm using a Duracell DURAGM-15L. Since I know Duracell doesn't make it, I looked it up. Here's what I found on batterylookup.com:
Duracell Ultra DURAGM-15L-US Sealed AGM Power Sport Battery Replacements
The Duracell Ultra DURAGM-15L-US distributed by Batteries Plus is a Sealed AGM motorcycle and small engine battery. Sealed AGM batteries come fully charged and ready to use directly from the factory. There is no need to add electrolyte or worry about acid eating away at your chrome. This type of battery can be placed into service on its side, is highly resistant to damage caused by vibration and resists freezing.
The DURAGM-15L-US battery comes with a 6 Mo. free replacement manufacturer warranty. It has 220 cold cranking amps (CCA) and its rated capacity is 14 amp hours (AH). This is a 12V battery. Some of the competing brands for this part number include: UTX14AHL,MBTX14AU,UTX14AHL-BS,YTX14AHL,ETX15L.
One of the East Penn Manufacturing Co. Inc. factories in Lyon Station, PA or Corydon, IA makes the DURAGM-15L-US line of batteries. They are the world's largest and most modern battery manufacturer with over 2 million square feet under roof. Many of the top automotive retail names including Advanced Auto have put their trust in East Penn to manufacture their high performance battery line. The original equipment (OE) battery found in many power sport vehicles that most closely relates to this one is the Yuasa YTX14AHL.
I've got a couple of years on it now and it's working well. Bike has Dyno Dave starter and, importantly, a 3 phase alternator system.