Battery or Charger Catastrophic Failure Mystery? With Pics

[E-Moto Tuner]

Had a catastrophic failure on either the batteries or charger on my E-Grom this weekend :

Checked battery voltage on the bike and it was low, 66v, after sitting for the last month and a half. Plugged the charger in and it started charging. Usually it takes around 8 -10 hours to charge the pack (6 x 20ah lead acid). Checked on it after 8 hours and there was a smell like rotten egg coming from the bike. Quickly unplugged the charger (which was still charging), turned off the breaker switch, and moved the bike outside. Pulled the side fairing off of the bike and saw at least one battery was swelled. Next day took out all batteries and 4 were swelled up a lot, and the other 2 slightly. Checked the voltage on the charger when plugged in but not under load with a multimeter, and it read around 83.9v which seems correct. Took charger cover off and all looked fine, no blown components.

Does this seem like a charger or battery issue? I would guess bad battery if one or two were swelled but with all 6 swelled it seems like charger issue except charger shows its charging at correct voltage when I did the multimeter test.

 

[E-Moto Tuner]

One more piece of info to add is that I had used an extention cord with the charger, one that I usually don't use, but I have used extension cords regularly and haven't had an issue.

Surprised that no one one the board here has any clue what may be the issue, usually there's a few of the more knowledgeable posters that would chime in.

 

[lnanek]

Any lead acid batteries I run into get dumped at the recycling center immediately and replaced by modern technologies, so no clue here. Didn't those ancient lead batteries need to be topped up with water occasionally or something? Or need some sort of de-sulphur-ization procedure that involved reverse current? No clue, I don't want them.

 

[LewTwo]

Overcharging a lead acid battery can produce hydrogen sulfide gas (smells like rotten eggs).

 

[E-Moto Tuner]

Overcharging a lead acid battery can produce hydrogen sulfide gas (smells like rotten eggs).

So that points to a bad charger then and not a bad battery. Makes more sense as don't see how a bad battery would cause the other 5 batteries to swell. Maybe under load the charger put out more voltage than the 83.9v it does when using the multimeter to test when charger is just plugged into the wall with no batteries charging.

 

[wturber]

I'm not at all an expert with lead acid batteries. I also don't know how much current your charger can put out. And finally, I don't know if your batteries started at about the same voltage or not.

So I'm thinking that if one battery was particularly low compared to the other batteries, it may have received a LOT more current than the others. If that caused the low battery to short some cells, then some other batteries might have started getting more current?

Were I to charge a bunch of lead acid batteries in series that had been sitting and were in a low charge state, I'd probably start the charge really slowly. But I'd also probably test the voltage individually first.

 

[gromike]

Overoltage charge, batteries toast.
An oppurtunity to get rid of the lead.

 

[Dui ni shuo de dui]

My guess would be that one of the battery was dead before you even charged the thing back up. Which could explain why your voltage was so low from the start.

Then you tried to charge everything back up, but the dead battery couldn't take much current so it went to the other batteries. Each battery saw 83.9V/5=16.8V, which is quite higher than what they could tolerate, so they ended up swelling and died.

 

[Zambam]

I see six batteries in the picture.

 

[wturber]

I see six batteries in the picture.

6 * 14v = 84v

12 volt lead acid batteries charge at around 14 VDC.

 

[E-Moto Tuner]

My guess would be that one of the battery was dead before you even charged the thing back up. Which could explain why your voltage was so low from the start.

Then you tried to charge everything back up, but the dead battery couldn't take much current so it went to the other batteries. Each battery saw 83.9V/5=16.8V, which is quite higher than what they could tolerate, so they ended up swelling and died.

This seems the most likely. The pack being at 66v, which is unusual, should have been a red flag for me. I knew it was out of the ordinary, but didn't realize it could overcharge.

Next time when I check before charging (which I usually do) and the pack is noticably lower than it usually would be with 6 good 12v batteries (which is usually around 72v) I'll make sure to check all batteries first so as not to "cook" the pack.

 

[Dui ni shuo de dui]

I see six batteries in the picture.

Yes, but since I assumed one died 6 becomes 5.

 

[Dui ni shuo de dui]

This seems the most likely. The pack being at 66v, which is unusual, should have been a red flag for me. I knew it was out of the ordinary, but didn't realize it could overcharge.

Next time when I check before charging (which I usually do) and the pack is noticably lower than it usually would be with 6 good 12v batteries (which is usually around 72v) I'll make sure to check all batteries first so as not to "cook" the pack.

Yes, and for whoever reads this, please note that it works just the same with lithium batteries and the exact same thing can happen (except the batteries will do a lot more than just swelling).

If you see a sudden drop in your battery voltage, NEVER charge it before making sure all the cells groups are still in balance. Usually if you do so your BMS should tell you something is wrong and it should turn off the charge, but you can't always rely on the BMS because some are defective/not programmed correctly. Most of the time when a battery catches fire it is for this very reason. I actually know a person who burned down his house because of this.

 

[Zambam]

Yes, but since I assumed one died 6 becomes 5.

Yes, if dead one was shorted (from charger point of view). If open circuit, 6 becomes 0?