FYI, Old school trick is to hold a long handle screw driver next to the back of the alternator (Mind the positive cable). The harder the mangetic pull on the screwdriver the more it's charging. So if you get into another "episode" you can check the alternator to see if it's charging 100%.

Hook up a volt meter to the battery while the engines running and monitor the voltage. If it peaks above 14.0v the regulator may be bad. If it stay below 13.5v but still fluctuates, then it's probably the brushes.

'86 Toyo 4wd
'04 600RR