Topic: Battery Boiling Noise after 35 mile ride @50-60mph

[cjackel]

After parking my 78 CB750 for the last two rides, I've noticed
the battery is making a boiling noise. Bike starts fine and operates normally.

I always put the battery on a tender after each ride and check the electrolyte level
once a month.

Is this a symptom of a impending battery failure?
Possible overcharging?
Thanks in advance.

[TwoTired]

The battery outgasses (looks like boiling) when it is at full charge and still receiving significant charge current.   Some is tolerable, a lot will probably shorten the life of the battery. Better to check the voltage at the battery while it is doing the outgassing.  Shouldn't go over 14.5 volts when you rev the engine.  If so, then there is a regulation issue.

By the way, the bubbles are hydrogen gas which is flammable/explosive.  Best to keep sparks and flame away from the battery and vent.

Cheers,

[eldar]

Bubbling usually comes when there is too much or too fast a charge. If this happens at higher speeds then I would check the regulator. Have you noticed you lights being brighter if you have ridden at night? I know there is a bit of a pick up from idle but does the light get brighter at higher rpm?

[cjackel]

Thanks for the tips.

I don't ride the Honda at night, so not sure if the headlight is brighter.
I'll check the voltage.

[Raul CB750K1]

That's a regulator issue. If you ride the bike at least once a month you really don't need the battery tender.

Raul

[Paul]

I used to hook my 500 up to a trickle charger on a regula rbasis, It's fine as it cuts out once the monitored ampage goes below the spec. ..........but since I started using it my battery only lasted about two months. (The same out gassing as you describe). This theoretically shound not cause any issues but since removing the trickle charger I've had no issues. (Charger is good, new and correct) so I think I was running slightly above the 14.5
Q: Have you the old type adjustable regulator or the sealed type.?

[cjackel]

My 78 750K is all original and stock, so whatever the original regulator was is the type.

[Paul]

Sorry C, I don't know which is standard, someone will soon tell.
My point was, if you have the adjustable one, you can regulate the voltage back to <14.5 if it's too high. Wheras I think the sealed ones need to be replaced. (But I shall stand corrected if necessary)

[eldar]

It should be able to be adjusted. The earlier Ks were adjustable too, at least some were. You have to remove the cover first though.

[cjackel]

I discovered during regular check of battery that the vent
hose was kinked.

The kinked hose caused battery acid to spill in battery compartment.

I cleaned the area with baking soda and water and bought a new battery.

[eldar]

Well sometimes it is the simplest thing. That is WAY easier than monkeying with a regulator.