soldered in new brushes, then checked voltage with motor running.
@ 3k rpm, 14.2v without load... 13.8v under about 14 amp load (engine, lights, heated grips on high) alternator putting 19.5 amps to battery at 3,000 rpm with or without above load.
charging system is working fine, no change after replacing brushes.
voltage regulator set for lead acid is too low to fully charge li-ion battery under load.
Sunday's 106 miles ride had several hours runtime. speeds was medium, rpms high. ran the motor hard! bright warm sunny day, headlight & taillight, ignition was only load on system. there was more than ample runtime to fully charge li-ion battery.
final voltage after a 106 mile bike ride with only lights on (heated jacket, grips, gloves on for last 20 minutes) was 13.2v or 70% charged for lithium iron phosphate battery.
conclusion is voltage regulator needs to be raised to 14.4v to fully charge li-ion battery. running any type load. that will reduce voltage down to 13.8v or lower. note conclusion is for this BMW R80G/S .. your bike's charging system may be different. but if your li-ion battery is not starting your bike cold and you are running heated gear. this could be part of the problem.
there is a HUGE difference between starting your bike with 13.20v vs 13.5v ... lithium iron phosphate discharge is very flat and only veri by about 1/2V for 80% of it's capacity.
Lead acid is fully charged at about 12.85v vs li-ion is fully charged at 14.4v then quickly scrubs off voltage to about 13.5v. don't discharge below 12.86v (DOD 80%) Charging systems are designed to fully charge lead acid batteries without damage. to optimize your bike for li-ion, voltage regulator should be raised to 14.4v.
hopefully tonight will drop to low 30's for a legit starter load test in the morning. topped Shorai LFX21 AH battery yesterday. wouldn't be fair to perform extreme load tests unless charging system can charge battery to full.
really looking forward to testing out Shorai 36 AH (pb eq)