Electric Bikes - New SLA Batteries charging noise (fizz / bubble)

Hello,

I own a BL-36 with an extended battery pack (12 Volt DC, 12 Amp Hour Lead-Acid Gel-Cell Batteries (x3) = (36 Volts 12 amps). After almost a year, I had a significant decrease in range. In the beginning, on an average run (couple low hills, stop and go's at traffic signals, riding half the way into head winds) I got about 17-18 miles. Now I get about 8-10 miles at a fast speed. I figured the batteries are used up and I need a fresh SLA battery pack.

I got as a gift from a family member 3 - SLA batteries rated at 12 volts 18 amps (36 volts 18amps), I wired them up exactly like the original battery pack. My question is, after I wired up the batteries and I plugged in the charger, after 5 minutes I can hear a faint bubbling noise and/or a fizzing noise coming from the new batteries. After about 30 minutes of charging, I can still hear the faint bubbling noise however, all 3 batteries and the wire harness are cool to the touch, and the charging box is warm to the touch (about the same temp as it was when charging up the old battery pack). The charger has the automatic shut off / trickle charge feature built in.

I did some research online about someone else with the same concern: a couple replies to the post said if a loud bubbling is heard it's possible that the batteries are over-charging. The last reply said that a faint bubbling noise on new SLA batteries are normal for the first couple days of recharging. Anybody have similar experiences like this? Any ideas on this subject would be helpful, thank you.

Follow Up: When my charger turned green (fully charged batteries) after a couple hours, the bubbling noise (more like a faint cooking noise) from my batteries, are now very faint to almost no noise at all.

When I used LA batteries, they never made a noise. Where are you charging them? If they exploded would it do a lot of damage?

Yes, I noticed on a recent purchase of SLA batteries, I noticed that noise when I charged them

that noise is normal with led acid. even used. its just air bubbles rolling off the plates. theirs more fluid in the cell when new.

I took my e-bike for a spin this morning, and it feels like it's a brand new bike..very happy and very fun. When I heard the "cooking noise," I did try to place the charging batteries away from flamables and anything I value...not much I can do with exploding acid but to be vigilant every 10 min.:twitchy:

Thank you for your replies.. I am better educated and have peace of mind once again.
:thumb:

Since the charger is charging the batteries in series it is looking for the total voltage only. Therefore, one cell may be at a higher voltage that the other 2.
Once a lead acid battery is charged above 15V it will generate gas from within.
That is the noise you are hearing.
Did you charge each battery seperately to make sure that they are all at their full capacity?
In any case, with use, the cells will balance out. It is really unavoidable unless you add circuitry to do charge balancing.

I did charge the batteries in a series. In addition, I am pretty sure the bubbling noise came from just the one battery-the battery that had the positive wire connected directly to the charger. Just as a side note, after my first test run of 18 miles with the new SLA batteries, I connected the charger to the batteries, and I could not hear that noise anymore(or it was so faint I couldn't hear it).