Strangest electrical problem

Got the motorcycle out today to get it running.  I had it on a maintainer all winter, and it showed 12.5v at the battery.

- Press starter button.  Cranks strong for a couple seconds, then I hear a click and it goes dead.
- Tested at the terminals, 4v
- pulled cables off the battery, cleaned with brake cleaner and scuffed with 120 grit until bright and clean, although they looked fine.
- 12.5 volts again, and the dash lit up
- press starter button.  Click and dead again.
- tested voltage, 4v.  Tested battery terminals UNDER the cables (like the actual Pb part itself) and it tested 4v
- removed cables, battery returns to 12.5v.
- reinstall cables, still 12.5v.  Hit the starter button, dead again and it reads 0.13v

I chased down every ground and found good continuity everywhere to the neg terminal, but even when I test pos to neg, I'm getting the same result... either 12.5 when it seems to be OK or 4v when it isn't.

Continue ad infinitum, and always getting voltages of either 4v or 0.1v.  I had the cables off probably a dozen times, and each time it revives to 12.5v, but as soon as you do anything it drops to almost nothing, and it tests the same when I probe the bolt on the cable or the Pb on the terminal.

Can a battery fail like that?  Makes great juice until you try to draw something?

Im no electrical genius but it seems like you are essentially doing load tests on the battery and it keeps failing.

Agreed, everytime I have a "weird" issue, its a failed battery. 

Also sounds like a bad battery to me.  Just last weekend I went through a similar problem with the Saab, although not quite so dramatic.  One day, the car just wouldn't start.  Put it on a charger for several hours and it was registering 12.6ish volts after being disconnected for an hour or so.  As soon as you turned the key and the fans started, the brake pump started, or the starter started, it would drop down to around 5 volts.  I agree that the battery is failing the load test.

I think the battery is bad too.  You could try disconnecting it, and then rigging up the battery out of your car with some jumper wires to see if the bike will start.

100% agree. Battery.

If it's not a battery, it's a bad generator with a short to ground.

How would the battery jump back to 12.5v after each "load test" though?  And why would it crank strong for a few seconds and then instantly die?  It wasn't like it drained down fast, it was cranking like gangbusters and then all the lights went out.

I also suspect the starter relay might be contributing to something.  It doesn't always click, it sometimes makes a crackly sound like the internal contacts are toast.  Good news is that it's $9 and it will be here tomorrow.

I'll load test the battery when I go to the FLAPS for oil.  If it's bad, it's still under warranty since I just bought it in September.

That seems like a bad connection inside the battery.  Any significant load an it opens.

APEowner said:

That seems like a bad connection inside the battery.  Any significant load an it opens.

Yep, I'd say you are right.

I had an old interstate that I brought back to life and used for about a year, then seemingly out of the blue the car was cranking and then it wasn't. Voltage measured fine until any load was put on it. One of the connections inside let go.

APEowner said:

That seems like a bad connection inside the battery.  Any significant load an it opens.

That is my thought.  It's like a loose terminal except inside where you can't do anything about it.

Evidence of the glazzies, me droogie: if the voltage at the battery is very low, it's the battery.   It is fun to theorize about what is happening in there, but it's a unified failure module, replace as assembly.

Definitely qualifies as strange.  Haven't seen that one before.  The internal connections are typically pretty beefy, so I wonder if something is shorting to bypass some of the cells.

Similiar Experience with the RAT Musang    New Battery solved the issue.  FWIW

So you were all right.  I charged it up overnight uninstalled and it showed 12.6v.  Took it to battery warehouse, and it load tested fine... for about 5 seconds, and then it dropped instantly to 4v.  The guy ran the test three times because he thought his tester clips weren't staying on.

He's puzzled too.  New battery, and she fires right up.