Expected voltage across battery - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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Where does this wire go?
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post #1 of 14 (permalink) Old 09-07-2015, 01:34 AM Thread Starter
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Expected voltage across battery

At idle I see 12v. At 6,000 rpm I see 12.5v. Is that right? I'm totally stock.

-Robert
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post #2 of 14 (permalink) Old 09-07-2015, 02:41 AM
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No, that is too low.

You want to see 13.5-14.5v @ 5k rpm. Check stator and r/r

1986 Kawasaki Vulcan 750
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post #3 of 14 (permalink) Old 09-07-2015, 07:49 AM
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Quote:
Originally Posted by thtanner View Post
No, that is too low.

You want to see 13.5-14.5v @ 5k rpm. Check stator and r/r
X2 You also want to see 12.5 - 12.8 at idle minimum.

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post #4 of 14 (permalink) Old 09-08-2015, 01:31 AM Thread Starter
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I charged the battery and cleaned the connection on the battery ground strap. After warming the bike up I still see around 12v while idling but when I bring it up to 5,000 RPM the voltage jumps to 12.5 and then slowly climbs to almost 14v in maybe 30 seconds and then bounces between 13.5 and 14. Is this normal? Is the regulator slow to react?

-Robert
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post #5 of 14 (permalink) Old 09-08-2015, 07:41 AM
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That's fine.

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post #6 of 14 (permalink) Old 09-08-2015, 08:36 AM
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That's fine.
Have to disagree. A battery that is putting out 12 volts is undercharged. Even showing 12.5 volts is low especially on our bikes. He should be getting close to 14 volts at 3000 rpms almost instantly, not 30 seconds at 5000. I would have the battery checked first, then check the rectifier.

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2001 Vulcan 750
marbled
TOC upgrade on ACCT
Air/fuel mixture set to 2 1/2 out
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Upgraded Mosfet rectifier
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post #7 of 14 (permalink) Old 09-08-2015, 10:48 AM Thread Starter
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I should mention the battery puts out around 12.5 with the bike off. The battery is several years old now. I've heard it's not uncommon for our bikes to discharge at idle though.

-Robert
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post #8 of 14 (permalink) Old 09-08-2015, 10:52 AM
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Quote:
Originally Posted by RobertGary1 View Post
I should mention the battery puts out around 12.5 with the bike off. The battery is several years old now. I've heard it's not uncommon for our bikes to discharge at idle though.

-Robert
Is the battery the "AGM" type?

If not, maybe it's time to upgrade to one.

If it is, 12.5 is too low of a 'charged' voltage for an AGM battery and it's probably toast.

If the charging system is healthy you shouldn't really discharge at idle, barely any charging sure, but it shouldn't eat the battery.

1986 Kawasaki Vulcan 750
NGK Iridium Plugs #7803/DPR7EIX-9
Duralast Gold ETX15 AGM Battery
Coastered & Shaved
TOC MCCTs
Metzeler ME880 [110/90-19, 170/80-15]
Balance Dampers Replaced
Tuxedo Mod
Rebuilt Forks w/ Progressive Springs
V&H Cruzers
VN750.com Grill Cover
Meanstreak Seat
Emgo 23-92411 Handlebars
MOSFET FH012AA R/R


1990 Kawasaki Vulcan 750

1998 Honda VFR800 FI

2014 Honda VFR800F

1989 Pontiac Firebird Formula 350
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post #9 of 14 (permalink) Old 09-08-2015, 12:28 PM Thread Starter
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Is the slow climb in voltage common?

-Robert
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post #10 of 14 (permalink) Old 09-08-2015, 12:37 PM
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I had a rectifier do that shortly before it died

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