05 zx10r stator alternator

What is the output voltage from the stator at the battery suppose to be?
Mine is showing 12.6V at idle and between 12.6V to 12.9V while reving the bike at 4000rpms.
When at idle it seems to be dropping voltage slowly.
need help please as battery keeps dying and I cannot start bike when out on rides.
I thought it was the HID light but have taken it out and gone back to oem light.
Mine is showing 12.6V at idle and between 12.6V to 12.9V while reving the bike at 4000rpms.
When at idle it seems to be dropping voltage slowly.
need help please as battery keeps dying and I cannot start bike when out on rides.
I thought it was the HID light but have taken it out and gone back to oem light.