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97 ZX9R Charging Voltage

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3.9K views 8 replies 6 participants last post by  ninjanut  
#1 ·
Howdy

Just got home and after I shut the bike off to chat to himself from next door, it was dead to the world.

This was tracked down to be a loose negative battery post and on that note, the black/yellow wire which I presume goes to pretty much everything up front was hanging by a thread.

I crimped a new ring terminal thereon and tightened it all back up, then ran the bike.

There is about 15.2-15.6V at the battery terminals at 4k, mainly settling to 15.2V.

Granted, this is not the world's best multimeter (DVM), bless its little cotton socks and it certainly doesn't stack up to the fleet of calibrated Flukes at work.

Is such voltage cause for concern? From idle to 4k, there is little fluctuation. But methinks that's a little high all the same.
 
#2 ·
For posteriority, I will include info for those who may follow in my footsteps.

I disconnected the alternator plug and backfed it from the battery with a diode - this will bootstrap the blessed thing into operation while protecting the battery from any untoward voltages.

And untoward they are. I'll delve in there with an oscilloscope later but I see 20-50V, rev dependent. So...replace the regulator in the alternator or - and this could be interesting - rig a system for it to excite the field winding from the switched live (set resistance) and use an external reg. That way one is not beholden to oddly designed things.
 
#5 · (Edited)
Righto. Time to update.

It turns out that the alternator works as follows - field coil excitation is proportional to desired output voltage....the only issue being this voltage is sensed after going from the battery, through the fusebox, up into the ignition switch and back.

Any high resistance in this path will cause erratic measurements.

Suffice it to say my 20yo ignition switch and multiple splicing afoot was some 20 ohms on that line!

Well - new loom and switch in place and voila...14.8V!
 
#6 ·
Hi can you please detail how you measured the 20 ohms exactly - just for completeness?
My ZX9R is also running about 15.x volts, and I had assumed it was just the regulator on its way out.
Found an eBay seller selling those aftermarket replacements - simple regulator on a stick of metal, and 2 leads by the looks of it. Got it cheap, so have one coming.
https://www.ebay.com/itm/232597285008
Curious if my issue is similar to what yours was...
Various bike shops over the years have said the regulator is on the way out...
 
#7 ·
Sorry for the late reply!

I removed both wires from the alternator (red and white?) and measured between them. All the red one is is switched power from the battery. Do this with the battery terminal disconnected. The white wire runs from the rectifier to the battery to the switch up front, through the switch (so as to not run the reg permanently) becomes the red wire and comes down to power/feed back voltage to the regulator.

If there is excessive circuit resistance in this line as there was in my case, it will sense falsely low and boost the output voltage to compensate

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