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Help!! It's 3am and I have a bubbling and squeaking battery! Answered

Please help!

I procured an electric wheelchair today (worn and torn, but in good shape.  It had 2 12v batteries, little smaller than an auto batt.  Didn't write down the amperage tho...The batteries were visually inspected for bowed or expanded sides, cracks, oxidation.  Everything appeared in order.  They have likely been sitting for some time.  Stupidly, I did not check electrolyte levels.  Oops.  Could easily be low.  I plugged the charger into the mainboard for 30 minutes, watching closely.  No issues, no overheating.  I left it for another 2 hours.  Again, no noticeable issues.  I tested the drive motors by controlling it around my driveway briefly. Power was very low.  It worked, but clearly lacked juice.

I plugged the batts in for another 4 or 5 hours.  But after that time, I noticed a crackling/squealing (faint) sound.  As if pressure was escaping.  Bad news.  I had the chair chassis (and batts) in my workshop, and now I was afraid it may blow, contaminating everything.  The batteries feel warm. One more than the other.

Beginning to panic, I threw on my goretex, respirator, goggles and gloves and carefully detached the battery cable from the main board.   I've never had one of this size blow, and have no idea what it could do.  very hesitantly, I rolled it into my garage, and closed the door.  Now I'm afraid to sleep, because I'm concerned about it.

Is this Normal old battery behavior?  Could this be due to low electrolytes?  A small crack in the case?  Is there anything I can do besides wait?  I'm not real anxious to go too close for too long.  Is there anything I can do that would not increase hazard?  I'm about to throw a tarp over it, but is there a high flammability risk if a high amperage 12v were to blow?

Guidance highly appreciated.  Thank you.


For Further information, it is not unusual for a battery to display those symptoms, when charging a battery if it has caps over cells you should check the water level and if it is low them fill it with distilled water... It will make hissing noise while charging especially if the water level is low......I suggest that you check the water level in the battery, and see if the charging that you did improved the functionality of the scooter .....

Thank you for this! I removed the batteries from the case, and it seems the positive terminal of on of the batteries has become loose. Little torque is required to produce movement in it. I suspect this was the noisy one. Fresh oxidation (since the other day) is apparent on this positive terminal. Scrapping the one, but will further test the one that appears "ok".

Thank you for the advice. Admittedly, it's been a while since I have charged a deep cycle battery (outside of the engine compartment). Also, based on what I can find online, the batteries appear to be "gel type". I'm assuming that this means it must be refilled with gel electrolyte?

Thanks again mstrfxit!

If in doubt toss it out.

Spot on. I ended up waiting to go to bed until almost 5am. Until the batteries cooled to room temp, and stopped making any noise. It all turned out fine, but every time I heard a loud noise, I was immediately awakened. But it all worked out.

The batteries are gone. I think locally I can sell them for recycling for $5-10. That will at least help me when I have to buy 2 more for the frame.

Looking back on last night, I suppose it may have been good it happened so late. I imagine someone might be very surprised if they saw me through the window dressed in goretex,gloves,goggles,and a respirator. : / Sure, I was preparing to protect myself from spraying acid, but that prob wouldn't have been immediately apparent.

My question now, is could this have been caused by low electrolytes? I haven't removed the batts from their cases yet, but there is not vapor dripping around the lid, or from the vent hole in the bottom. As I said, I've never had a deep cell 12v blow before. Anyone experienced this? Is it violent, or is it more of a general release of pressure. I know the vapors are flammable, but in a room with no open flame, could a large battery cause a fire or explosion?

This was a very uncomfortable experience. I intend to learn from it.

You wheeled it into the garage? Next time wheel it outside.

What was your charge rate vs battery rating? it sounds like you over charged the battery more than anything else. Not a battery expert, just my thoughts.

I know, the garage was probably not the best option, but the garage is the next room over from my workshop. Since the chair has been stripped to the base chassis only, to push it anywhere, my face would have to be within proximity. Wasn't worth the risk.

The charger came is designed for use with this specific controller and battery set. It is a 3A 24v automatic shutoff charger. The batteries are not really marked at all. "MK Battery" is all that identifies it. Even web searching doesn't reveal the capacity of the batts (at least that I can find).

Was definitely not over charged. They were put on the charger at 0.3v, and currently have ~5-6v.

Thanks for the input!