Hi all,

Reposting this thread in the proper section.

Hopefully someone can shed some light on what I'm dealing with here. Thank you in advance.

Issue: brand new battery from o'reilly that was installed on my bike couple months ago just went dead out of the blue seems like it. Will provide more details below, but bike has been on the tender since the new battery was installed for most of its time (less than 3 months total since installed). It was taken off the tender for about a week before I did go for a ride about 100 miles, bike has been starting up every time on first try during this trip. Got home parked the bike in the garage turned it off and took out the key. Checked on the bike 3-4 days later and battery is completely dead! Got a volt reading of 5.10, light were not on, key position was on off position with key not in the bike. WTH happened? How could a nearly new battery discharge in less than 4 days on its own? Leads me to believe there is something else causing battery to die early.

History: Of course if it was my first battery that went bad I would probably not think much about it and just buy a new one and be done. However, It seems that I'm having too many issues around batteries. When I just picked up this bike about 4 years ago it had a bad regulator, which I have replaced. Sometime later I replaced the battery. Was able to use replaced battery for about 2 years, I didn't always keep this battery on the tender and some point it discharged and wouldn't start the bike, but was still cranking though. Placed that battery on the fender was able to recharge it enough to get it started, kept on the tender since then, went on multiple rides no problem. Until I went on a 150mile ride, after about 100miles on the trip, stopped to get gas. 2 mins later the bike would not crank at all. Ended up buying a new battery while on this trip from o'reilly, closest shop. Didn't think much about it then, couple year old battery went bad after I let it discharge once. Even though it seemed strange that the previous battery would die so sudden after the bike has been running for about 100miles.

Now combining the history I had with battery issues and then this new battery dropping to 5.10v I'm starting to question if there is another issue somewhere with my charging system. How would I go about trouble shooting and identifying the root cause?


UPDATE/Troubleshooting:

I ended up getting a brand new battery (replaced from o'reilly). Before removing old battery, I did inspect positive/negative cables mounted to the engine case and on battery itself, all seemed to be tight and I didnt notice any rust/corrosion. Have read the charging system sticky along with many other threads and youtube vids and still not 100% sure If I did it all correct.

When I start the bike, DC voltage goes up 13.90-14.07 with 60 degrees outside, when I rev up the engine even past around 6K RPM it doesn't go past 14.07 is it normal?

Trying to follow Step 2 in the sticky. Im using a multi meter for this step. Can I please get a confirmation here if Im doing it right?
-I have meter set on DC voltage
-Unplugged connector from regulator to battery cable
-Measuring other plug connector that goes from regulator to round/orange stator cable. Red lead on one of the 2 prongs of regulator connector and grounding to an engine case bolt.
-Results: one of the prongs shows -.001 and 2nd prong shows .000 or sometimes -.000.
-Questions: Am I testing the correct regulator plug? Are the above results suggesting that I have "some" voltage and that regulator is bad?

"Step 2. To check the regulator unplug it from the stator. Take a test light and clip it to the negative terminal of the battery and then touch first one pin and then the other on the plug that goes to the regulator. If you get even the slightest amount of light from the test light the regulator is toast.
To do this with a meter: black lead to battery ground, red lead to each pin on the plug, start with the voltage scale higher than 12vdc and move voltage scale down in steps for each pin. Any voltage is a bad regulator."


Now moving onto testing the Stator.
-I set meter to Ohms and measuring the round/orange stator cable
-Results: meter shows .02 ohms then drops to .01 ohms and then if I keep on holding the leads inside the cable then reading drops to 00.00.
Questions: Is this normal for reading to drop or this indicates problem with stator?

"Step 3. On the other part of the disconnected regulator plug. Set the multimeter for Ohms x1 scale and measure for resistance across the pins of the stator. You should read something around 0.1 to 0.2 ohms for the TC88 32 amp system."

Checked the continuity with positive lead inside the stator cable and negative lead on engine case bolt and reading OL, is open loop same as infinite resistance?

"Step 4. Then check for continuity between each pin on the plug and frame/engine ground. The meter needle should not move (infinite resistance)(digitals will show infinite resistance) if the meter needle does move (indicating continuity)(digitals will show some resistance), recheck very carefully. If the meter still shows continuity to ground the stator is shorted (bad)."

-Set meter to Ac Voltage
-Placed both leads inside the stator cable, 1 in each hole touching the metal sleeves
- Results: at idle getting 23.6-29.98 volts, when give it a good rev volts go up to as 60 volts. Not sure how to verify if my numbers are within spec, since I dont have a tach/rpm reader on my bike, not sure how many RPM my idle is.
-Questions: Do I have a 32 amp system on my 08 Nightster? Since manual book says Im running on 30 amp maxi fuse. Also do I need to maybe replace Maxi Fuse? Upon visual inspection with a light Im not seeing any burn damage/noticeable damage to the inner fuse.


"Step 5. Set the meter to read A/C volts higher than 30 volts (the scale setting for voltage should always be higher than the highest voltage you expect or you may fry the meter). Start the bike, and measure from one pin to the other on the plug (DO NOT cross the multimeter probes! - touch them to each other). You should read roughly 16-20 vac per 1,000 rpm."

"32 amp system produces about 16-20 vac per 1,000 rpm, stator resistance is about 0.1 to 0.2 ohms."

 

if you followed the fsm trouble tree then you are good to go.
when my 01 sport system went south, EVERYTHING tested good on the several times i had issue (three times) till it finally showed issues that the meter caught. so what was it???
when the stator is wound, they make a jumper from winding to regulator pigtail and glue this to the stator frame. well this glue broke down and allowed current to flow through the oil to ground and eventually burned the wires at the connection on the stator. this caused intermittent charging issues. IF you have enough wire left, just reconnect and insulate, unfortunately mine did not so i replaced the stator.

 

I wrote this for touring bikes. Hope it helps:

Testing:

Connectors and cables should be checked and cleaned first. Loose and corroded connectors, terminals and grounds can cause high resistance, impeding current flow. Check cables for broken or rubbed insulation and check continuity to make sure the conductor is not broken inside the insulation.
Coating connectors with dielectric grease will keep moisture out and reduce corrosion.
Use the schematics in the HD Electrical Diagnostic or Service manual to determine the location of additional connectors.


Battery testing:
First check and clean battery terminals, Battery cables and ground connections. To check cables, disconnect one end and Ohm out, wiggle while testing. Cables can and will corrode and the evidence can be concealed under the insulation.
If you are unsure of the battery’s condition charge it fully and take it to an auto parts store and have it load tested.
Voltmeter test:
Connect voltmeter positive to positive terminal on battery and voltmeter negative to battery negative terminal.
12.7 v = 100% charge
12.6 v = 75%
12.3 v = 50%
12.0 v = 25%
11.8 v = 0%
Watch the battery voltage when you start the bike, if a fully charged battery falls below 9.6 volts it’s time to replace it.
If a well charged battery runs down if the bike sits for a short time perform a current draw test. Set your meter to read 10 amps current. Pull your main fuse and insert the meter leads. Here’s a list of components and what current they will draw in milli amps, 1/1000 of an amp) from the 2015 manual:
LHCM 0.5
RHCM 0.5
Speedometer/ IM 0.5
Regulator 1.0
ABS 1.0
BCM 1.0
ECM 1.0
Security Siren 20.0
Radio 0.5
Amplifier 0.5
CB Module 0.5

If the Battery passes all tests check the charging system.
Charging System Testing:
Volt meter set to DCV 20V scale or higher.
With the bike in neutral and voltmeter attached to the battery, start the engine and rev to 3,000 rpm. If the voltage measures 13V – 14.7V the charging system is operating properly. If less than 13V test the Stator first. If Greater than 15.5V test the Voltage Regulator.

Stator testing
Turn the bike off and disconnect the Stator from the Voltage Regulator.
Testing a 3 phase Stator, (A single phase stator is tested in the same manner but the plug will only have 2 sockets).
The end of the connector from the stator has 3 sockets. Set your meter to ohms and connect one lead to the battery negative. With the other lead make contact with the conductors inside each socket. You are checking for a grounded coil winding, each socket should show an open circuit to ground, no continuity.
Now take both meter leads and check resistance between each of the three sockets, 1-2, 2-3 and 1-3. The resistance should be 0.1 – 0.3 ohm.
Next check the Stator’s AC output. Set the meter to ACV 100V scale. With the Stator unplugged from the VR and the bike in neutral, start the bike. Run the bike at 2,000 rpm and check the Stator output between sockets 1-2, 2-3 and 1-3. The voltage should read approximately 32-46 Volts AC, for the 50 amp Stator. Stators with other Amp ratings will be similar.
If the Stator continuity tests to ground and Phase to Phase are good but the output is not the Rotor may be bad.

One other indication that the stator may be bad is if your primary oil smells like a burnt circuit board.

Voltage Regulator Testing

Voltage readings of 15.5V and higher test wire from VR negative to battery negative, if less than 0.5 ohm replace Voltage Regulator.
If the output is less than 13V from the Voltage Regulator to the battery and the Stator output is good, disconnect the output cable from the VR to the Battery. Check continuity between the Voltage Regulator Positive wire and the battery Positive and the negative wire and battery negative. Repair or replace cable if needed. If the cables are good and the Stator tested well replace the Voltage Regulator.