Accessory vs Battery Voltage - TESTED - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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  • 2 Post By Spockster
  • 1 Post By ubertalldude
 
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post #1 of 9 (permalink) Old 04-03-2017, 11:36 PM Thread Starter
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Accessory vs Battery Voltage - TESTED

My initial take on the matter:

Took my little voltmeter and tested the voltage readouts at the accessory leads in the headlight bucket and the voltage at the battery terminals. Pic attached.

Result: the voltage reads the same at both ends. 12.5 V from both ends.



Updated result: I am a big fat liar! I tested it again with a multimeter and there IS a voltage drop, which may be due to a MOSFET R/R because the charging is being taken out of the junction box

After switching to a MOSFET my voltage meter was consistently reading 13.5v at full engine speed, and dipping as low as 11.0 when idling at stops with the voltmeter wired through the accessory leads in the headlight bucket.

After rewiring the voltmeter directly to the battery I am getting 14.0v at speed and 12.4v at idle (no charging at idle, expected with a stock stator to some extent, though not desirable)

tl;dr - If you're adding a voltmeter it is best to wire it directly to the battery terminal leads if you want accurate voltage readouts, especially if you run an aftermarket R/R


ignore the attached image. It represents the electrical system at rest, not under load/charging
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Last edited by ubertalldude; 06-29-2017 at 05:31 PM. Reason: I was wrong, there IS a voltage drop
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post #2 of 9 (permalink) Old 04-04-2017, 10:13 AM
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Not sure why you'd think there was an "issue"... if you connect wires from a voltmeter to the battery it's not going to give a different reading if you are basicly just making the wires longer. (To a point of course, there is a guide on how long a wire can be for a given gauge of wire before the problem of resistance kicks in)
I wired my voltmeter to the accessory leads, which also powered my driving lights and a small LED. Worked fine.

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post #3 of 9 (permalink) Old 04-04-2017, 11:01 AM
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Thanks for checking, uber.

Why? Because it's been posted around here that there's a considerable voltage drop between the two locations.
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post #4 of 9 (permalink) Old 04-04-2017, 11:29 AM Thread Starter
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Never thought it was an issue, more of a curiosity. Figured I might as well check it out before I installed that voltmeter in the dash.
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post #5 of 9 (permalink) Old 04-27-2017, 07:03 PM
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I have a 2000 Vulcan 750 all stock except for a Shindengen SH775 regulator. The voltage at the accessories leads in the headlight bucket and at the battery terminals are the same with ignition on, bike not running. At idle, they are close but at 3K RPM I have a one volt drop at the accessory leads. any ideas on what could be causing this voltage droop?
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post #6 of 9 (permalink) Old 05-16-2017, 01:20 PM Thread Starter
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Quote:
Originally Posted by Vulcanizer View Post
I have a 2000 Vulcan 750 all stock except for a Shindengen SH775 regulator. The voltage at the accessories leads in the headlight bucket and at the battery terminals are the same with ignition on, bike not running. At idle, they are close but at 3K RPM I have a one volt drop at the accessory leads. any ideas on what could be causing this voltage droop?
(replying months after your question, I know BUT)

I think this is actually normal, as I have updated in the original post. I was testing while not charging, and since a Mosfet/Series regulator is not attached thru the junction box/wiring at all, just direct to the battery.
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post #7 of 9 (permalink) Old 05-16-2017, 01:36 PM
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Likely simple resistance. Your voltmeter has testing wires how long and what gauge? The accessory leads go through the junction box, a fuse, and then travel how far? What gauge are they?
A one volt drop is nothing unless you're talking about charging voltage. All the lights/electrics on the bike are rated for 12 volts. You won't see any difference in them unless the voltage drops below 12. At higher rpms I was getting 14.8 volts at the front accessory leads.

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post #8 of 9 (permalink) Old 05-16-2017, 01:57 PM Thread Starter
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Yeah, kinda what I was thinking. My voltmeter in the dash might also be wonky and inaccurate, but 1v drop is nothing to be worried about, but definitely worth noting if you're relying on it to indicate your charging state. So long as you've got 13.5v+ at the battery terminals you're charging. 14+ is preferable, but 13.5+ is acceptable and does the job fine
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post #9 of 9 (permalink) Old 06-29-2017, 05:33 PM Thread Starter
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adding a reply to bump this for anyone who read the original posting, as I have corrected myself based on recent modifications, testing, and rewiring. Sorry for the misinformation, should have known to test the system under load, NOT just at rest!
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