Need help, what is the root cause for battery discharge?
Hello Folks,
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?
It's fairly easy to test voltages at the battery, as well as your stator output. Do you have a multimeter? Harbor Freight has them free with coupon sometimes. You can check for any discharge when key is off as well. Might check your ground connections on the engine and be sure all cables are free of corrosion internally and externally.
There are Stickies in the Tech Electrical section on checking your charging system. You'll need a multimeter for testing, which will also help with John's suggestions above. First task however is to remove the battery and charge it using a proper charger (not a tender), then get it tested. That is all spelled out in the Stickies.
I'm back with more findings and questions. 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, so should be good there.
"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."
There's only a couple of things that would cause this. I've been through it before.
Rule out the battery since you've now got a good one.
The regulator either works or it doesn't. There's not much to it. Make sure the contact points are clean and the connection is good.
Follow the negative cable from the battery and make sure that the ground is clean and tight.
Most likely it's your stator and most likely it grounded to the case and because of that is not properly charging the battery.
Unhook the plug that goes into your regulator down by the frame. Switch your meter to AC and plug one lead into each hole on that plug. Doesn't matter which one goes in which hole. It should put out around 40-60 depending on RPM. If you're getting that then you need to move on and check to see if the stator has grounded to the case.
Set your meter to Ohms and put one lead into one of the holes on the plug and stick the other lead to a good ground on the motor. There should be infinite resistance. It should NOT be a closed circuit. Do the same for the other hole on that plug. If either one shows anything besides infinite resistance, the stator is grounded and needs to be replaced. The service manual should tell you how to do it, it's not super difficult.
Here is a new vs old. In this case, a bunch of crud and metal shavings attached themselves to the windings and bridged a gap to the engine case grounding it out. The cable could also be stripped somewhere and it would cause the same issue.
Last edited by maverick31210; 01-02-2018 at 05:30 PM.
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?
YES.......that is normal! Doing exactly what it should be doing!!
Thank you for your feedback. I did test the stator I got results/question below:
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?
"Set your meter to Ohms and put one lead into one of the holes on the plug and stick the other lead to a good ground on the motor. There should be infinite resistance. It should NOT be a closed circuit. Do the same for the other hole on that plug. If either one shows anything besides infinite resistance, the stator is grounded and needs to be replaced." I did this as well and and getting Open Loop/OL reading. Is OL same as infinite resistance?
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?
YES.......that is normal! Doing exactly what it should be doing!!
MURPHCC1,
Thank you for your feedback. Does extra 15* really make a difference and will get me up to at least 14.3? I'm just concerned that if all is charging properly, then why am I having so many issues with batteries going bad. If this was my first encounter with a dead battery I would just move on and keep on riding, however, at this point I have no trust in this bike not knowing if it will just die on me at any time I go out for a ride.
According to the sticky "Start the engine and measure DC Volts across the battery terminals, the regulator should be putting out 14.3 - 14.7 vdc at 3600 rpm and 75 degrees F. "
12-03-2017, 02:11 PM
Need help, what is the root cause for battery discharge?
