Originally Posted by JRWooden
It appears you have a magic alternator or a miscalibrated VOM ....
Could we trouble you to unscrew your R/R and post the markings on the back?
Thats all normal, it's just variance between meters. Notice resting voltage is 13.1. Lead acid does not rest that high once the surface charge is gone, it rests at 12.84 at the absolute most.
All the meters on this thread are varying, mostly up which is the way they usually drift.
All readings have shown the voltage higher at idle and lower at RPM except for NCD's which is the only one that is also a charging at a higher voltage that seems real.
I'm completely satisfied. The F800 idles at around 14.1 volts and at rpm is around 13.85, from first year through the one I checked this afternoon which was another 2012, with at least one exception but i'm going to say that is super rare.
ebrabaek, thanks, I did indeed laugh when I saw that meter, partially because I used to have one just like it, about 20 years ago :) The old Micronta meters were actually very good. I might still have mine but it exploded when I tried to measure voltage on a 2000 amp 480 buss with the leads in the wrong jacks.
If you get it, the BK 5491B is an awesome meter! Takes forever to turn on, but so does my fancy fluke. Once it boots up, the 5491B is fast, accurate, and just laid out very user friendly. I don't own one, but used it at a friends lab.
For the mere mortals on this thread..... HERE
is a 1 hour review of 5 cheap multimeters.
is the cheapest meter I own and would feel fine about taking with me on a cross continent ride.
Money no object? THIS
is the multimeter I wish I owned for everyday shop work and rides to the four corners. Will double as offensive weapon.
Towpro, You hit the nail on the head. LiFePo4 needs to internally heat to provide full cranking amps, and not just when cold. Even warm LiFePo4, batteries that will start your bike fine have a large voltage drop for the first few seconds. Enough so, that even on a warm day, the the battery recommended for some bikes by some manufactures will be damaging bikes starting systems over time IMO.
The K100 isn't the only bike who's starter relay can weld together or just burn up, I have seen this happen on two F8's as well, though both with crappy oe batteries.
Further, though its not an issue with the F8 since its starter uses a sprag clutch to transmit starter power to the crank, some bikes including the BMW boxer bikes use a bendix or solenoid to force the starter pinion onto the flywheel ring gear.
On these bikes, under voltage during cranking will over time destroy both the starter and ring gear, necessitating removal of the transmission to repair on the BMW boxers.
I'm going to get into cold weather tests and all of the above, but first I have to find a LifePo4 battery that passes my tests when warm, which the LFX18 from Shorai does not.
Stay tuned :)