I was looking at this thread http://www.advrider.com/forums/showthread.php?t=395505&page=5
when I came across this post:
"F800GS/F650GS Electical System Capabilities
Measurements made by Joel Wisman on new F800GS
Amps Watts * Notes
Key on 1.8A 25W *1.74 amps if kill switch is in kill position
Key on, high beam on 5.7A 77W
Low beam on (baseline) 10.8A 147W * Add other current draws to this value
High beam on 4.1A 56W
Heated grips low 2.0A 28W Max draw
Heated grips high 3.4A 46W Max draw
Cooling fan 4.7A 64W
Alternator output (held at constant 13.6 volts)
1280 rpm (idle) 17.7A 241W *94 watts over baseline load
3000 rpm 25.9A 352W *205 watts over baseline load
4500-7500 rpm 27.8A 378W *231 watts over baseline load**
* Measurements made while holding voltage to 13.6 volts. Watts = Amps x 13.6 volts.
** System can deliver 27.8 amps (current-limited) at 14.4 volts, or 400 watts (per BMW spec)
Current draw after turning engine off with key:
First 3.5 seconds 830 milliamps Computer shut-down, etc.
Next 3 seconds 170 milliamps
Next 54 seconds 88 milliamps
Thereafter 1.3 milliamps For clock and volatile memory"
It could explain why some batteries and stators give up.