Alternator or battery: Voltage output different at 2500 RPM

I have an XJ650 and noticed some funny issues with my charging system. Last night, I noticed that the charge level of the battery affects charge voltage at 2500 RPM. I took some different measurements on two different days. It seems that the 'initial charge' as described as 'REST (OFF)' affects the output at 2500 RPM. Does it mean the battery might be at fault?

Measurements (May 8, 2016)
REST (OFF) 12.24 volts
REST (ON) 11.91 volts
STart engine 10.2 - 9.8 volts

RPM (1500) 12.7 volts
RPM (2500) 13.3 volts



Measurements (May 9, 2016)
REST (OFF) 13.38 volts
REST (ON) 11.92 volts, 12.72 volts (**multiple measurements)
STart engine forgot to check

RPM (1500) forgot to check
RPM (2500) 13.76 volts, 14.18 volts, 14.4 volts, 14.65 volts. (** multiple measurements)


Another link to the same discussion: http://www.xjbikes.com/forums/threads/charging-issue-motorcycle-just-dies.89708/#post-513931

 

To get the 13.38v in your 5/9 data, were you connected to a charger? Or is that a typo, and you mean 12.38v?

 

NO apparently not a typo. I had just disconnected the charger and plugged the voltmeter to plug that is connected to the battery. Perhaps my voltmeter is bad.

You had asked previously about my battery life and it's a 2 years to date - a Yuasa YB12AA installed on Mar 30, 2014.

Can the battery affect the voltage at 2,500RPM?

 

You should wait at least a hour after taking it off the charger to take the initial rest reading. Before that your reading surface charge that is high and mostly goes away as soon as a load is put on it