I was reading the owner's manual to my Edirol R-09HR, and on the battery replacement page it mentions to only use type HR15/51 for rechargeables. The reachargeable Duracell 2650 mAh batteries that I had in the unit for testing purposes say "HR6". I'm not sure what the difference is, and failed to find information about this anywhere. Does anyone know what these numbers mean? Are they the same batteries (HR6 and HR15/51)? The unit was working fine off the HR6s, but I want to make sure I am using the right type of batteries. Thanks.