battery draining while riding

[Eric_in_OR]

I'm not much of an electrician, but I understand the basics just enough to get me in trouble; but this bike has me stumped. Help please!
Bike is a 2005 GS500F with 14k on the odometer, 7k of which has been in the past 3 months. Electronics are unmodified, except that I replaced the dash lights with LEDS when I bought it 2 years ago. The problem below started a month ago.

• I am sure that the battery is good, but it is a 9 month old Everstart ES12BS. Bike & battery can sit off in the garage unhooked from the tender for 3 days and maintain a 13.40v charge.
• 
  If I ride the bike for about 300-400 miles, at the 2nd gas stop of the day, the battery will no longer have enough juice to start the bike.
  I can push start it, and all runs fine again until the next gas stop, and then I must repeat until I can charge it overnight with the tender. After a ride like this, the battery will have a voltage of <6v
• Dash lights flicker (LED), headlight is dim, and tachometer is erratic after about 100 miles. Dash lights brighten when RPMs are increased, but practically invisible in daylight at idle.
• At 2500rpm the voltage measured at the battery terminals is 14.25v.
• At 5000rpm the voltage measured at the battery terminals is 13.60v.
• I have traced the wires and checked the connections, and didn't find anything that appears out of order.

It seems clear to me that the battery isn't getting charged sufficiently by the bike, but the voltage readings while running seem to indicate that it is. I was confident that it was a stator/rectifier issue until I tested the voltages, now I'm not so sure. Any ideas here? I find it odd that the voltage is consistently higher at low RPMs than it is at higher RPMs, is that normal? It's getting a bit embarrassing having to push start when I stop on longer trips!

[Paulcet]

You're right, the voltage shouldn't decrease with RPM.  I suspect a bad voltage regulator.  But first check the stator voltage: http://www.bbburma.net/Documents/JohnBates_ChargingCircuitTests3.pdf

<edit>
Further thinking...  This is the 2nd time I have heard of decreasing voltage with RPM.  Not sure if the other one was truly a bad regulator.  The Suzuki regulator (like just about all regulators until the last few years) are terribly inefficient, and actually cause the stator to run at full load all the time.  Here is a better way.  That thread says that it is normal for voltage to decrease with rpm on shunt regulators.  If I have another regulator failure, I will be converting to a series regulator.  Either the Shindengen FH012AA or Cycle Electric CE-600 series.

[bombjack]

• At 2500rpm the voltage measured at the battery terminals is 14.25v.
• At 5000rpm the voltage measured at the battery terminals is 13.60v.

Are you sure about those readings? The voltage at 2500 should be a 13.5 V and then increase with rpms.
Disconnect the three yellow wires that goes to the regulator input and connect a standard H4 bulb. Now start the bike. The bulb should light up VERY bright. Don't rev the engine to high or you'll blow the bulb. If the bulb does not light up VERY bright, check the AC voltage between all of the three yellow wires. They should all read around 75 V AC. If not, your stator is toast.

[Jared]

Have you let the battery sit for more than three days to check it's condition? Your charging voltage seems to be right/within spec if memory serves...(I doubt they changed the charging system when they put bodywork on the bike..) 13.5-15.5  volts at 5k rpms is the right range.

Do the laundry list of checks again-- Check and clean all the connections- check the wires coming out of the RR and see if any are burned or baked. Check the stator etc ( I assume you have a manual?). Battery condition, connections, stator ,RR.  I wouldn't rule out a failing battery yet...( they can go bad from long periods of  not being used..).

Here...Kerry did a nice post long ago...


http://gstwins.com/gsboard/index.php?topic=38480.msg431967#msg431967

[Elijafir]

I would not rule out a failing battery at all.
13.4V on a battery that is not hooked up to anything is "over charged."  It should not ever get above 12.6V or 12.8V (can't remember..)  Just because it will hold Voltage with no load doesn't mean it isn't hosed.  It could be holding Voltage just fine but have no "Amp Hours" left.  If there is an interstate battery supplier near you they should have a good battery tester that can test your Cranking Amps (Should be between 160-200+.) 
It is kind of odd that it would slowly die while it's hooked up to your charging system.. but, the fact that you can push start it and keep going indicates to me that your charging system is fine.  (We don't need batteries to run vehicles.. just to start them.)
IF your battery is good.. You can try testing your charging system by starting the bike and disconnecting the POSITIVE lead from the battery. BE VERY CAREFUL NOT TO LET IT TOUCH ANYTHING METAL, DON'T TOUCH ANYTHING METAL YOURSELF, AND ONLY USE ONE HAND (keep the other behind your back so you wont be tempted to use it.)  IN CASE YOU DO "GROUND OUT" IT WONT PASS THROUGH YOUR BODY!  (don't be scared, you have to touch something "positive" and "negative" to get "shocked."  14VDC is barely enough to feel with dry skin, anyway.)  If the bike dies.. there is your answer.  If the bike stays running... test your Voltages at the battery leads, not the the battery terminals. 

[Eric_in_OR]

• The stator is putting out 65v on all three pairs.
• RED multimeter-lead to the RED positive output wire of the RR, BLACK multimeter-lead to the yellow wires: nothing, which probably means that it is over the 1.2v limit of my multimeter. Presumably this means that all is good? I'll have to get another multimeter to test it again.
• BLACK multimeter-lead to the BLACK/RED output wire of the RR, RED multimeter lead to yellow wires: 0.5v
• BLACK multimeter-lead to the BLACK/WHITE output wire of the RR, RED multimeter lead to yellow wires: 0.5v

It looks to me like like I have a bad battery. That's good news, I suppose, but not very interesting!