18 EC300 Battery not charging

[Neil E.]

Haven't had much time to think about this. Could you put a toggle switch on the bike to disconnect the battery any time you shut off the engine? I don't mean disconnect the heavy cables, just where the voltage regulator/rectifier supply would reach the battery. The idea being to open any path that would be a parasitic draw. This should keep the battery voltage OK.

We should find out if the voltage reg/rect is really carrying the load of the machine. Normally the R/R output voltage does not vary much. At idle with the lights on it might drop to 12V, but should be around 13V at anything above idle. If voltage drops below 12V, then the battery is carrying the load.

The battery is not meant to do much more than start the bike. As soon as the engine is running the stator should take over from the battery. What about mounting a voltmeter on the bike? This could verify that you are getting the correct voltage from the stator and R/R at all times.

Going back many years all cars had ammeters on the dash board. My Studebaker would always display current flow. A minus value meant the battery was carrying the load. A plus value showed the generator was carrying the load. This was a better indicator than just voltage, but you had to know what it meant.

[Tech]

FIXED

Replaced the diode attached to the relay.

Battery charged to 13.66 volts after a two day 110 mile ride.

Notes on testing the electrical system leading to solution:

#1 Regulator/Rectifier testing - The RED wire is the DC voltage output. Voltmeter (+) on the RED R/R terminal, voltmeter (-) on GROUND. You will get varying DC voltage w/ motor running if R/R is good. View G main wiring diagram.

#2 Diode testing - The RED wire is DC voltage input to the diode. Voltmeter (+) on the RED wire, voltmeter (-) on GROUND. You wil get varying DC voltage if diode is receiving DC voltage/current from the R/R.
The YELLOW/RED is the DC voltage output to the relay. Voltmeter (+) on the YELLOW/RED diode terminal, voltmeter (-) on GROUND. You will get varying DC voltage if diode is good & outputting to the relay. Views I & J main wiring diagram.

#3 Diode/Relay/Battery relationship - DC voltage & current to flow only one way. The diode allows DC voltage & current to pass thru the relay via the YELLOW/RED wire & on to the battery. See lower right corner of main wiring diagram.

#4 Dashboard Charging Meter - This meter only indicates DC voltage is being generated by the R/R. It does not indicate the battery is being charged.

#4 Main wiring diagram - As referenced in my original post, the wiring harness battery interface in the diagram is poor & confusing.

I hope this thread saves some other owners some grief, time & $$.

[Neil E.]

Good job. Your notes will help the next person with a similar problem.