Say What? Too much charging?

Wilf · Post by **Wilf** » Sun Jun 20, 2010 3:43 pm

So, your engine vibration is due to a bent crankshaft which causes the rotor to spin closer to the 2 pairs of headlight stator coils and thereby provides more than normal power through the pink headlight wire and thus, the high voltage readings?

This is just a really off-the-wall guess, but if it truly is the case, I might consider bending my crank to boost the charging voltage...LOL

Wilf

Wilf · Post by **Wilf** » Tue Jun 22, 2010 1:37 pm

Brent,

I did some work this morning with the charging graphs in the Honda Shop Manual and I'm thinking your voltage measurements are ok.

At 5000 rpm the graphs show charging voltages of 16.9 with headlights off and 16.8 with headlights switched on.

You should be good to go, and I'm no longer thinking about bending my crankshaft!

Wilf

Wilf · Post by **Wilf** » Tue Jun 22, 2010 1:49 pm

teazer,

Voltage regulation with a zener diode is not as simple as you and I might want, and that's probably why it doesn't show up on these machines.

It's not just a matter of slipping a high wattage diode and heat sink into the circuit--it would have been done by now. For a zener to work as a regulator there needs to be a current limiting resistor in series with the load (the current demanded by the bike). That introduces complications of its own. What Honda has done is to balance the load requirements with the AC generator outputs, and that seems to have worked reasonably well over the years so long as nothing is done to seriously upset that balance.

Wilf

e3steve · Post by **e3steve** » Tue Jun 22, 2010 3:26 pm

Zeners were used on late-60s/early-70s Meriden BritShit; a bloody disaster and the lazy way to voltage regulation. No place within our technological capabilities yesterday or today. Honda's balancing act was waaaaay more advanced by comparison...... IMHO!

teazer · Post by **teazer** » Tue Jun 22, 2010 4:55 pm

FYI many bikes use the Zener approach to voltage regulation.

I rode enough CB72/77 over the years without problems so I agree it should be possible to get away with such a crude arrangement as Honda designed back in the late fifties.

A bigger issue with a ZD is that it basically dissipates electrical energy as heat and these bikes don't exactly have surplus power to throw away.

Wilf · Post by **Wilf** » Tue Jun 22, 2010 5:48 pm

teazer,

Yes, indeed Zener diodes have been effectively used as voltage regulators in all sorts of applications. They work very well when the supply and load have been designed with Zener regulation in mind. The problem here is that the supply from the AC generator was not designed with Zener regulation in mind, so retro-fitting becomes very complex, and, because a Zener requires a current limiting resistor, somewhat wasteful in its most simple configuration.

I'm thinking "elegant" more than "crude" as a descriptor for Honda's design--not much there to screw up or fail...

Wilf

Goodysnap · Post by **Goodysnap** » Tue Jun 22, 2010 8:42 pm

I keep forgeting that I own and enjoy a 45 year old motorcycle. I would normally cringe at 17 Volts on a 12V system. With no regulator in the system it makes sense to me now. That stator is gonna keep pumpin juice no matter what. I guess I should be greatful I have a good functioning charging system. Hopefully if I get this vibration under control I can keep this light from blowing out. Thanks everyone.