Need help with alternator/battery problem - Honda Shadow Forums : Shadow Motorcycle Forum

mattj230 · 09-04-2007, 04:17 PM

I have a 1985 vt500c. I had been keeping it outside under a shelter but just recently had to leave it outside and uncovered. It stayed that way for about a week and when I went out to ride it the battery was completely dead. I have never had any problems with the battery before this. I was able to jump the bike and it started right up and sounded fine when it was just idling. When I started riding it it would do all right in 1st gear when I was moving slowly, but as I accelerated the engine would start to cut out. It was fine as long as I was moving slowly but if I tried to go faster it would start to cut out. If I slowed down it would be fine and it never actually cut off on me, but I couldnt get going faster than about 15 mph. When I got it parked again I cut it off and the battery was still completely dead, nothing would turn on. I dont know what drained the battery or what is causing these problems. I thought maybe it was the alternator but the bike ran fine when idling even though the battery was completely dead. If anyone has any ideas on what is causing these problems or has any advice for me it would be greatly appreciated.
Thanks

mikemilburn · 09-04-2007, 04:45 PM

Possibly the battery is toast and just decided to pick that time to die totally. A bad battery, one that is shorted internally, will suck almost every bit of juice generated by the charging system.
The only way to accurately tell is to put the battery on a slow charger and have it load tested. just because it shows 12.5 -13.5 volts doesn't mean it's any good.
If that shows the battery is good then post back and we can go from there....Mike

meester_jamie · 09-04-2007, 04:46 PM

to start off with... undo the neg terminal on the battery,, and put a 1 amp charger on the battery terminals ,, overnight.

measure the voltage at the battery terminals,, with the charger off.. you should get about 12.4 volts..
if not... take it to a shop that tests batteries. we have starter or alternator or battery shops that test for no charge..

Make sure there is nothing on.. key off.. and put a test lamp between the battery neg terminal,, and the wire you took off.

If the lamp is bright,, there is a good load,, or a short
if the lamp is dim,, there is a tiny load... or a high resistance short
if the lamp is dark.. that is good.

If you find the lamp on at all... you have to find out what the load or the short is.. is the brake light switch stuck on.. or I dunno...

write back to

mattj230 · 09-05-2007, 09:42 AM

I will try that out and come back if it doesnt work. Thanks for your help.

mattj230 · 09-06-2007, 12:40 PM

I took the battery to a dealership and they charged it and load tested it for me. They said it was good. I put it back on and the bike started right up. I tried a test lamp the way you described and could see no light at all. I rode it around for about 15 minutes and it gave me no problems. When I stopped I tried turning it off and cranking it a few time and it was a little sluggish but it started. I came back about 4 hours later and tried starting it again and it acted like it was trying to start but it didnt have enough juice to turn over. Could it be that even though the battery load tested ok right after they charged it it is still bad and I need to get a new one?

mikemilburn · 09-06-2007, 04:58 PM

Not ruling out the battery wasn't checked properly, but it sounds, to me anyway, that the system is not charging.
Don't forget it's hard to diagnose something without actually being there, not doubting anything you say but there could be something that would slap a person in the face should you be in front of it and have seen it before.
The times you describe as far as starting, running, starting again etc. sound as if the bike is running of the battery and the battery only.
There is a good troubleshooting chart whose location I can't remember, that'll lead ou thru a sequence of test for the charging system. Someone will post it I'm sure shortly
In a nutshell you check for 70-90VAC directly from the stator when running around 3000rpm. Should be 3 yellow wire and you check between any two. Note that it's AC not DC you're looking for.
If that checks out you then check the DC voltage at the battery, approximately 14-14.5VDC.
Wait till someone posts the site for the chart, do your checks and post back. If you're not sure post back and ask questions.....Mike

herbyreed · 09-07-2007, 12:15 PM

If I were you I would get a digital multimeter (about $15) and also buy a trickle charger that has terminals that you can attach to the battery and leave on. Then you have a way of charging the battery on the bike - batteries last longer if they are put on a trickle charger in the winter every couple of weeks. And with the terminals attached to the battery it is easy to hook up the multimeter while the bike is running or not. A fully charged battery should be 12.6 to 13 + volts. A properly functioning charging system should yield 13.5 to 14.5 volts, depending on the rpm. You can get more accurate figures by consulting the specs for your bike in a shop manual - but if you are getting less than 13.5 volts at about 2500 rpm the charging system is probably not keeping up and the battery will discharge. Many vehicles will continue to run even though the battery may be discharged beyond the point where it could run the starter so that is not always a good measure of whether the charging system is keeping up. I would charge the battery up, start the bike up, and hook up the voltmeter. See what numbers you get. There is always the possibility also that the charging system and battery are fine but there is a short or bad electrical component somewhere that is sucking off power and draining the battery, possibly even when the bike is not running.

I would also add that if the battery is more than three years old I would tend to go ahead and get a new one (get a maintenance free gel type if you can) and then run your charging tests.

mattj230 · 09-08-2007, 02:12 PM

I got a multimeter and this is what I found. With the bike turned off I got about 11.4 volts across the battery terminals. With the engine on and running at about 3000 RPM I got 13.6 volts. I think I am going to buy a new battery and try everything again.

09-04-2007, 04:17 PM	#1 (permalink)
mattj230 Junior Member Join Date: Jul 2007 Location: Raleigh NC Posts: 4	Need help with alternator/battery problem I have a 1985 vt500c. I had been keeping it outside under a shelter but just recently had to leave it outside and uncovered. It stayed that way for about a week and when I went out to ride it the battery was completely dead. I have never had any problems with the battery before this. I was able to jump the bike and it started right up and sounded fine when it was just idling. When I started riding it it would do all right in 1st gear when I was moving slowly, but as I accelerated the engine would start to cut out. It was fine as long as I was moving slowly but if I tried to go faster it would start to cut out. If I slowed down it would be fine and it never actually cut off on me, but I couldnt get going faster than about 15 mph. When I got it parked again I cut it off and the battery was still completely dead, nothing would turn on. I dont know what drained the battery or what is causing these problems. I thought maybe it was the alternator but the bike ran fine when idling even though the battery was completely dead. If anyone has any ideas on what is causing these problems or has any advice for me it would be greatly appreciated. Thanks

09-04-2007, 04:45 PM	#2 (permalink)
mikemilburn Senior Member Join Date: Mar 2005 Location: Hardwood Lands, N.S., Canada Posts: 671	Possibly the battery is toast and just decided to pick that time to die totally. A bad battery, one that is shorted internally, will suck almost every bit of juice generated by the charging system. The only way to accurately tell is to put the battery on a slow charger and have it load tested. just because it shows 12.5 -13.5 volts doesn't mean it's any good. If that shows the battery is good then post back and we can go from there....Mike __________________ '82 Suzuki TZ750 -sold- '99 750 Shadow ACE -sold- '04 Vulcan 1500 Classic VROC 21458 http://www.maritimevulcan.ca/

09-04-2007, 04:46 PM	#3 (permalink)
meester_jamie Senior Member Join Date: May 2006 Location: Galt On. Canada Posts: 387	to start off with... undo the neg terminal on the battery,, and put a 1 amp charger on the battery terminals ,, overnight. measure the voltage at the battery terminals,, with the charger off.. you should get about 12.4 volts.. if not... take it to a shop that tests batteries. we have starter or alternator or battery shops that test for no charge.. Make sure there is nothing on.. key off.. and put a test lamp between the battery neg terminal,, and the wire you took off. If the lamp is bright,, there is a good load,, or a short if the lamp is dim,, there is a tiny load... or a high resistance short if the lamp is dark.. that is good. If you find the lamp on at all... you have to find out what the load or the short is.. is the brake light switch stuck on.. or I dunno... write back to __________________ Full Patch Crazy Canucks Rider Southern Ontario Chapter #1 http://www.canuckriders.com/

09-06-2007, 04:58 PM	#6 (permalink)
mikemilburn Senior Member Join Date: Mar 2005 Location: Hardwood Lands, N.S., Canada Posts: 671	Not ruling out the battery wasn't checked properly, but it sounds, to me anyway, that the system is not charging. Don't forget it's hard to diagnose something without actually being there, not doubting anything you say but there could be something that would slap a person in the face should you be in front of it and have seen it before. The times you describe as far as starting, running, starting again etc. sound as if the bike is running of the battery and the battery only. There is a good troubleshooting chart whose location I can't remember, that'll lead ou thru a sequence of test for the charging system. Someone will post it I'm sure shortly In a nutshell you check for 70-90VAC directly from the stator when running around 3000rpm. Should be 3 yellow wire and you check between any two. Note that it's AC not DC you're looking for. If that checks out you then check the DC voltage at the battery, approximately 14-14.5VDC. Wait till someone posts the site for the chart, do your checks and post back. If you're not sure post back and ask questions.....Mike __________________ '82 Suzuki TZ750 -sold- '99 750 Shadow ACE -sold- '04 Vulcan 1500 Classic VROC 21458 http://www.maritimevulcan.ca/

09-07-2007, 12:15 PM	#7 (permalink)
herbyreed Senior Member Join Date: Aug 2007 Posts: 188	If I were you I would get a digital multimeter (about $15) and also buy a trickle charger that has terminals that you can attach to the battery and leave on. Then you have a way of charging the battery on the bike - batteries last longer if they are put on a trickle charger in the winter every couple of weeks. And with the terminals attached to the battery it is easy to hook up the multimeter while the bike is running or not. A fully charged battery should be 12.6 to 13 + volts. A properly functioning charging system should yield 13.5 to 14.5 volts, depending on the rpm. You can get more accurate figures by consulting the specs for your bike in a shop manual - but if you are getting less than 13.5 volts at about 2500 rpm the charging system is probably not keeping up and the battery will discharge. Many vehicles will continue to run even though the battery may be discharged beyond the point where it could run the starter so that is not always a good measure of whether the charging system is keeping up. I would charge the battery up, start the bike up, and hook up the voltmeter. See what numbers you get. There is always the possibility also that the charging system and battery are fine but there is a short or bad electrical component somewhere that is sucking off power and draining the battery, possibly even when the bike is not running. I would also add that if the battery is more than three years old I would tend to go ahead and get a new one (get a maintenance free gel type if you can) and then run your charging tests. __________________ 1998 Shadow 1100C3 Aero Black and Burgundy

09-05-2007, 09:42 AM	#4 (permalink)
mattj230 Junior Member Join Date: Jul 2007 Location: Raleigh NC Posts: 4	I will try that out and come back if it doesnt work. Thanks for your help.

09-06-2007, 12:40 PM	#5 (permalink)
mattj230 Junior Member Join Date: Jul 2007 Location: Raleigh NC Posts: 4	I took the battery to a dealership and they charged it and load tested it for me. They said it was good. I put it back on and the bike started right up. I tried a test lamp the way you described and could see no light at all. I rode it around for about 15 minutes and it gave me no problems. When I stopped I tried turning it off and cranking it a few time and it was a little sluggish but it started. I came back about 4 hours later and tried starting it again and it acted like it was trying to start but it didnt have enough juice to turn over. Could it be that even though the battery load tested ok right after they charged it it is still bad and I need to get a new one?

09-08-2007, 02:12 PM	#8 (permalink)
mattj230 Junior Member Join Date: Jul 2007 Location: Raleigh NC Posts: 4	I got a multimeter and this is what I found. With the bike turned off I got about 11.4 volts across the battery terminals. With the engine on and running at about 3000 RPM I got 13.6 volts. I think I am going to buy a new battery and try everything again.

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