Electrical troubles

This is weird. I've read that a "rotten egg" (H2S) smell associated
with a motorcycle battery indicates overcharging. But I just noticed a
pronounced H2S smell when I tried to start my bike. And it hasn't been
moving for well over a week. The battery will not hold a charge, and
I've been slowly doing experiments and measurements. Today after
measuring the battery at 13.0 volts, I tried to turn the engine over,
though I knew it wouldn't have the oomph. I was right about that.
That's when I smelled the H2S. I may have kept at the starter switch
for longer than I usually do. Maybe that had something to do with it.

Anybody have any info on what's happening when you smell H2S while
trying to start with a weak battery?

Thanks.

 

What I think is happening is that you've got one cell in the battery
shorted out and your charging system is working as hard as it
can to keep the voltage up. While it's doing this, it's also boiling
off the acid, hence the H2S smell.

I'd test the battery and buy a new one quickly if it was bad before I
destroyed expensive charging system components. (Unless of
course the H2S is something you ate.).

 

It's an aftermarket sealed MF type. What sort of test do you have in mind?

I should also have said that the bike is very high-mileage and may
likely have reg/rect problems. It's just that I've been having so many
problems with the battery holding a charge (getting somewhere and can't
get back without a jump start, e.g.) that I don't think the problem is
OVERcharging.

More on charging: I did the test to check the basic charging function --
was supposed to read between between 13.5 and 15.0 at 5000 RPM. Got
13.48. Figured that was not good, but didn't explain the total
inability of the battery to hold a charge.

Tested that. Ruled out.

Thanks!

-r

 

I had mine load tested recently at Roadrider. Charge it up using
a battery charger, not the motorcycle charging system. If it won't
come up to a good voltage and stay there then you pretty much
know it's bad.

If it'll come up to a good voltage, apply a load (they've got a
testing device for this) and see how much the voltage drops.
If the voltage drops below a certain point, you know it's
shot.

I'd really recommend this. When I brought mine in, they told
me the battery was good so I looked elsewhere.

As I said, I think the battery is bad. They occasionally loose
one cell, so the voltage will drop below 12 as soon as you
shu the bike down. If it's a bad battery and you don't swap it
out, you soon will have a reg/rect problem even if you don't
have one now.

The test was free and they explained they didn't need to sell
me a battery. What more could anyone ask for ?

See above. If one of the cells is bad, it won't hold a charge.

 

OK, battery test it is.

Thanks, Rob and Brian!