86 VFR750 Voltage query....dropping as revs increase?

Aloha,

Here's one that I'm finding as odd. At Idle, Voltage at Battery is 14.0. At 5000 rpm it's 13.2-13.4

What gives? Battery is fine, reg/rectifier is NOS and alt checks out on all 3 poles. The bike operates as the Honda gods intended....just thought it was weird.

Whatchathink?

KK

 

Funny, been thinking of asking the same question re my 4th Gen. Anything above idle to about 2500rpm shows a healthy 14+, at 5000 with the brights on it sometimes gets as low as 13.5. Even when you back off the throttle the voltage starts to climb. Any electrical boffins out there that know why this is, or is it a sign of impending doom?

 

When the battery is already full (12.8-13.6), then it no longer needs to be charged. The RR has a shedding circuit to dump the excess voltage thru the frame to ground. That circuit consists of some combination of device such as zener diode, SCR, FET or bipolar transistor-- and there can be from 0.3 to 0.7 volts drop across the device when on, and this may account for some of the voltage difference.

Another possibility is that you have a high resistance in the paths between the RR and the battery terminals on either or both the positive and negative--check for loose, dirty or corroded terminal lugs or damaged wiring. This would add a voltage drop that the RR must overcome and cause it to pull the shedding lower to compensate.