My 990Adv suddendly started acting similar...
At rest 12,7v,
Engine started 13,4v
At revs >2,5k 12,9 - 13,1v
Hard to start, a few weeks ago, a freeway stretch at >100mph, stoped at fuel station, battery dead. After jump starting with cables from a car, returned home and when arrived at garage hit the start again and fired fairly well. A few other rides and it seems the faster i go, the less charge it get...which is consistent with voltages above. This may be good to avoid speeding tickets but adds alot of stress about having the big-twin not cranking properly when necessary..
battery is brand new. I'm either leaning to bad VR or faulty battery.
Coincidence it start acting like this when battery was replaced