Need help with an issue on an 09 Nightster

[neilrl79]

My brother has an 09 Nightstar that is eating batteries at an alarming rate. I'm assuming that something in the charging system is shot. Can anyone point me in a direction that will diagnose the problem? I'm not sure how many miles are on it, probably near or over 20k.

 

[user_deleted]

neil: you talking 2009 sportster here? and does it have a factory alarm system? it is "eating batteries" for one of 3 reasons that you need to narrow down:
1-hard discharge while sitting unused
2-over charging while running
3-insufficient charging while running.
#1 diagnosed with inline multimeter set to DC AMPS between disconnected NEGATIVE cable and NEGATIVE batt terminal. report back with finding.
#2 diagnosed with simple volt gauge while riding. report back with findings.
#3. """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
that's all you need right there. the charging system simple alternator/VR/etc as on any evo sportster....virtually same as all XB's.
and why did i ask about the factory alarm? thousands of them on both small and big-twins thru the last decade have caused battery issues. that is what #1 above is for.

 

[neilrl79]

neil: you talking 2009 sportster here? and does it have a factory alarm system? it is "eating batteries" for one of 3 reasons that you need to narrow down:
1-hard discharge while sitting unused
2-over charging while running
3-insufficient charging while running.
#1 diagnosed with inline multimeter set to DC AMPS between disconnected NEGATIVE cable and NEGATIVE batt terminal. report back with finding.
#2 diagnosed with simple volt gauge while riding. report back with findings.
#3. """"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
that's all you need right there. the charging system simple alternator/VR/etc as on any evo sportster....virtually same as all XB's.
and why did i ask about the factory alarm? thousands of them on both small and big-twins thru the last decade have caused battery issues. that is what #1 above is for.

Yeah it's a sportster. Not sure about the alarm.

Thanks for giving me a starting point John, my knowledge of the charging system is almost nonexistent.

 

[user_deleted]

sure thing neil and the charging system on it should be almost mirror image of all the XB's. first thing i would do is access the fuse box, remove the cover....then do #1 i listed above for you. with multi meter set to DC AMPS do the probe. if you see anything more than approx. 1/5th of an amp...or 200 milliamps...start pulling a fuse one by one till you see large change in gauge reading. when you see it that is the culprit circuit. then let me know what you found.

 

[neilrl79]

sure thing neil and the charging system on it should be almost mirror image of all the XB's. first thing i would do is access the fuse box, remove the cover....then do #1 i listed above for you. with multi meter set to DC AMPS do the probe. if you see anything more than approx. 1/5th of an amp...or 200 milliamps...start pulling a fuse one by one till you see large change in gauge reading. when you see it that is the culprit circuit. then let me know what you found.

I'm going to go over his place tomorrow, I'll definitely post my findings.

 

[neilrl79]

No significant draw with the bike off.

With the bike running at about 1000 rpm I got a reading between 13.9 and 14.2 volts, I'm not currently set up to have a voltmeter on it while riding. I have a little LCD voltmeter that I'm going to wire up for him to get a better idea of what's going on while riding.

I tested the AC voltage output of the stator and the reading was within spec according to an HD forum I found.

I did get a better understanding of what is actually happening. It seems that on several occasions he was riding along and the bike just died. Starter clicked as if it had a dead battery when he tried to restart it. After getting a jump start the bike ran fine. It makes me wonder if some component is failing when it gets hot.