question about voltage readings - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 10 (permalink) Old 10-01-2006, 03:22 PM Thread Starter
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question about voltage readings

you might remember my electical issues from this thread: https://www.vn750.com/forum/showthread.php?t=2393.

as a recap, my ignition switch was cutting the power off sporadically while i was riding and immediately after one of the 'power off' incidents, the voltage readings spiked up to 17 volts. when i got the bike back to base, i discovered that the r/r had been fried. also discovered that the negative battery lead had snapped off (not sure if this happened when i was taking the lead off the battery or while i was riding).

so... new ignition switch, new electrosport r/r, new negative battery lead.

i took the bike out for a test ride today. at 5000rpm, the voltmeter was reading about 14.5 volts. when i got the bike up to 6000rpm, the readings dropped to the low 13's... 13.1, 13.2 volts. when i pulled off the highway and stopped at a light (idling at 1000rpm), the readings were in the low 12's... 12.0, 12.1 volts.

two questions: 1. is the drop in voltage when i increase the speed from 5k to 6k rpm just a product of the regulator 'regulating'? it seems like 5k rpm is the sweet spot for the r/r. 2. at idle, 12.0 volts seems a little low. does this seem right? granted, it was fairly warm out today and the fan was probably running, but anything less than 12.5 volts scares me a bit.

the only thing that comes to mind is replacing the battery. this battery is new as of july... just wondering if the incident with the voltage spikes might have damaged the battery.

paul
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post #2 of 10 (permalink) Old 10-01-2006, 03:46 PM
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At 5K and at 1K, the readings are about right. If the fan came on at 6K, then the readings are about right. If not, then I dunno. But 5K and 1K are correct.

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post #3 of 10 (permalink) Old 10-01-2006, 06:54 PM
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It sounds to me that the regulator is doing it's job... Although it looks like the voltmeter has too much voltage drop from the battery. I suspect the regulator is regulating correctly at the 14.5v cutoff but the meter is reading low, the idle voltage is probably about 13-13.5 volts read with a voltmeter at the battery. The regulator should then begin regulation at about 14-14.5 volts.

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post #4 of 10 (permalink) Old 10-01-2006, 07:18 PM
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Quote:
Originally Posted by global_recon
when i pulled off the highway and stopped at a light (idling at 1000rpm), the readings were in the low 12's... 12.0, 12.1 volts.
Don't forget, if you were using the brakes, you'd probably get quite a drop from the brake lights.


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post #5 of 10 (permalink) Old 10-01-2006, 07:24 PM
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The readings are correct. I'm sure he's running it from the battery. At idle, especially at 1000 rpms, the stator isn't producing enough voltage, so that's actual battery voltage that you see. Our batteries are not like car batteries, our batteries have a standard voltage of 12.5 volts. If the bike is turned on, especially with the headlight on, then the voltage will read lower.

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post #6 of 10 (permalink) Old 10-01-2006, 07:52 PM Thread Starter
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the readings i specified were taken from a datel voltmeter wired to the accessory leads in the headlamp enclosure. i know cegodsey said he'd seen a .4-.6 v (i think) difference between readings taken at the accessory leads and readings taken directly on the battery, but i just checked and i'm getting only a .02 v decrease at the accessory leads.

i just started the bike again (it had been sitting for a few hours cold) and the voltmeter was reading 12.7v at idle. when i hit the brakes, it drops to 12.5v. maybe the earlier lower readings (12.0/12.1v) were due to heat [?].

paul
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post #7 of 10 (permalink) Old 10-01-2006, 07:59 PM
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Very possibly.

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post #8 of 10 (permalink) Old 10-02-2006, 12:54 AM
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The other guys have pretty much summed it up, at idle the stator isn't producing any significant current at any significant voltage. Think of it like this, when the bike's idling, it's running off of the battery. Period. That's why it's so important to have a healthy battery, better yet an AGM, maintenance free battery. It's also why you don't want to take your bike in any parade that lasts more than 10 minutes. Remember, don't worry about the voltage at idle, it's not suppose to be idling, it's suppose to be crusing

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post #9 of 10 (permalink) Old 10-02-2006, 12:57 AM
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Quote:
Originally Posted by Ironman
it's not suppose to be idling, it's suppose to be cruising


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post #10 of 10 (permalink) Old 10-02-2006, 05:55 PM
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Have you moved your r/r away from the goats belly? That added heat might account for the lower voltage at idle after the bike has heated up real good.

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