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Electrical gremlin ....tracking it down

Charging System, Wiring, Lighting
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zoom
honda305.com Member
Posts: 132
Joined: Sat Oct 16, 2010 9:26 pm
Location: Willmar, Mn

Electrical gremlin ....tracking it down

Post by zoom » Tue Mar 26, 2013 7:07 pm

Need some advice how to track this problem. I know zero about my olhm meter and how to use it. Just finished restoring a 64 dream. Runs great, shifts, etc Just about done except fr this issue. New oem type battery from eBay, new old replacement stock type horn and lamp switch. So this last Saturday after I got it tuned and running good I put it to bed ( prob ran about an hr and a half total ) I had used the starter a lot and you could tell the battery was running low. During the running, the tail light worked in the two key positions like it supposed to and the headlight worked at first , but quite after awhile . Never to come back on. speedometer light worked. When I put it away I hooked up my new "smart" charger on it, settings were small battery, norm setting. It showed only 25% charged and it started charging. The next morning it showed 100% charged. I left it on. It's supposed to shift into a maintain mode. Well today I went to do some other things on the bike and the battery was dead, I mean like real dead, charger still on. Water/acid level was down below the add mark ( this was a new battery 3 weeks ago and filled with new acid at my local battery store) . Battery was cold.
thinking my battery got cooked somehow. The store is checking out the charger and seeing if they can bring the battery back to life, though I doubt it
I am thinking that some circuit is open and the charger kept trying to keep charging it. No fuse burned out. Key was off, no visible light on. How do I track it down. Headlamp light burned out. Can I hook up an old 12v car battery that I have around and use an ohm meter to track if I got a drain someplace? Or would a simple test light do the same? Point me in the right direction

cadman
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Posts: 386
Joined: Sat Dec 08, 2012 5:12 pm
Location: Georgetown, TX

Post by cadman » Mon Apr 08, 2013 8:46 pm

Turn your meter to VDC so you can measure DC volts. A fully charged battery will be about 12.7 VDC. As you turn on stuff - headlight - the voltage will drop. When you use the starter the voltage will drop - Should stay above 9 VDC. If you were sitting in the garage idling the charging system will not keep up. The engine RPM is to low to provide enough charging power.

Before starting check the battery voltage - Now start the bike, head light off, and read the voltage as the engine speeds up. The voltage should go up. With the head light on it will be less but at any rate you need to be at least close to 13VDC minimum to keep the battery charged.

With everything off disconnect the negative battery cable and lightly flick it against the negative battery post. If you see any spark something is drawing current.

Your small charger is good for maintaining a charged battery but will not work for charging a battery that is low to start with.

Provide more info as you test

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