Emergency- How do I handle over-charged batteries?

J

John in CR

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Due to a charger failure I've got a severely overcharged battery pack. It's 10s of Ford electric car cells that are puffed into an arc. The bolt on connections are sheared off of most, an apparent safety feature, but it leaves me no way to discharge to relieve some pressure, if that's even recommended. They're under such pressure that I'm a bit afraid to even move the scooter with what seems like a 1kwh bomb with a rat trap trigger.

I'll get pics to share later. At this moment the arc of over-charged cells are wedged in place with the bottom corners held by the diy steel battery tray. The arc is pushing against the steel top tube, and the ends are wedged now against the rear mono-shock in back, and a steel strap at the front.

Hopefully my ES friends have some advice. In the meantime, |'m getting to work removing anything flammable from the area including but not limited to 8kwh of a car pack in a wooden crate less than a meter away. Plus there's another 2kwh of fully charged pack in the battery trays under the overcharged section.

My biggest questions are whether or not these things are in an explosive state, and how to best handle them. Once the sun comes up in a few hours the rise in temp might even be a trigger, so I need to work fast.

John
 
Wow! How fast can you take as many components off the scooter? I can strip mine down to close to a bare chassis in less than an hour. I'm thinking about a controlled burn here. Take as much stuff off of the scooter and drench with water before "trigering" the bomb? Once the battery is burnt, you only have to clean up and repaint the chassis? I don't know, it's difficult to come up with ideas without being there to see how things are. It might be scary just to be near it. Holy crap just think ahead and be careful, this is serious shit.
 
It's not going to explode. You've ruined the battery, so break out the tool kit.

Remove the battery and put it somewhere it won't harm anything if it catches fire, which at this point it probably won't do but it pays to be safe.

To discharge the battery I might shoot it and set fire to it. Or just sell it on Craigslist as it. YMMV.
 
redilast said:
How over charged are we talking here? What is the cell voltage?
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No way to measure the cells. Poles are sheared off. Based on the partial cell measurements at different points that have exposed metal my best guess is about 5V/cell.
 
flat tire said:
It's not going to explode. You've ruined the battery, so break out the tool kit.

Remove the battery and put it somewhere it won't harm anything if it catches fire, which at this point it probably won't do but it pays to be safe.

To discharge the battery I might shoot it and set fire to it. Or just sell it on Craigslist as it. YMMV.
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I don't think it would explode outright. I'm more worried about it catching on fire as I relieve pressure stress unbolting the straps and rack to get it off the bike.

The overcharged section was warm when I got to it, and the charger had gone to green so it wasn't still charging, so hopefully there was already some internal shorting that discharged some of the energy. At least since it's cooler now and was fairly warm at first, that I'm less worried about changing temps of the day will start a chain reaction. It's outside but shaded with nothing flammable in reach, so not worried about a fire all that much, though I don't want to lose the scooter.

Into a tub of water outside is where
 
flat tire said:
It's not going to explode.
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Define... "Explode".

Overcharged Lithium Ion can produce hydrogen gas, so extremely rapid redox is not out of the question. And what is an explosion, except a pressure wave caused by extremely rapid redox?

That said, pretty unlikely, but quite a vigorous combustion, I would think is likely if violently disturbed.

I'm thinking welder's mask, big bucket of salt water, and try to get it out and into the water ASAP, but I'm no expert... Just watched enough LiPo fires when I first got into the game.
 
Sunder,

Thank goodness these weren't RC lipo like I used to use, or Tesla or other highest energy density cells, because the bike would have surely flamed out.

Thanks for the reminder to bring home my welding gloves and helmet tonight.

Lesson learned...absolutely never again charging without a timer set to cut power to the charger, since even chargers proven trustworthy for years can flake out for no apparent reason. I'm familiar enough with my packs to know how long to set a timer, and since I only charge to 4.1v/cell and use large format packs with relatively slow chargers, my set times will still allow full charge with extremely low risk of going past 4.2V even in a worst case. That is assuming a charger can't change it's own CC current limit.

Charging risk will be a moot point soon once I get my home pack up and running. I'm going to 30s for the house pack that will be balance charged as 3 10s pack by the solar system. I'll have ebike charge connections with different connectors for each type 10s, 20s (my most common) and 30s. A simple circuit to limit current will give me an impossible to overcharge system as long as I monitor cell balance.
 
My concern would be that sat at high voltage it's going to be continually decomposing electrolyte so the gas formation may get worse the longer it's left. Is there nothing left of the terminals to get a croc clip onto and discharge? I'm guessing the battery box isn't sealed so you can't fill it up to flood and discharge the cells. Can you lay soak rags/sponge over the tops to possibly discharge them some?
 
Hey John! If you can get them into a tub of water with a cup of salt in it, it generally safely slowly discharges them in a safe way. Definately do it outside because the gasses it bubbles up are mostly splitting water, but may have hazardous gasses involved. Also, set the tub in a place that you wouldn't mind having a bonfire happen if they behave poorly.

Also, the longer they sit at a very high SOC, the more gas they are producing inside so they will tend to keep swelling. After a week or so submerged in a tub of salty water they should be stable-ish and safe-ish to drop off at a recycler.
 
Thanks for the concern and advice Punx0r and LFP.

I don't know if I can deal with it tonight after almost no sleep and 14hr work day. The idea of building of more gas and pressure is a concern. I seriously doubt I can remove the rack without sparks involved due to the pack pressing against steel, so I gotta strip it down to nothing but what's holding the pack in place and shape.

I was thinking that since it didn't already flame out that I could wait to deal with it Saturday, and with a little luck I get the pack out without event, bolt a new one together, so I have this fun and reliable transportation back in service same day. Oh well, at least my new and for the first time beautiful ebike will be operational in a day or 2.

If I get the motor, controllers, and lighting off uneventfully then maybe I'll just push it out in the yard, mix up a salt water solution and start spraying it from the distance with my hose driven garden sprayer from a distance.

It's windy, so no chance of gas concentrations...what about puncturing the cells with a pin or fine nail to release the pressure?
 
If you can't get them out of the frame I would be tempted to very carefully prick them if it's possible to do so. It's just doing it without causing an internal short that could possibly provide the ignition source you're trying hard to avoid. So perhaps a non-conductive cocktail stick and go in at a shallow angle, if possible, in a location away from the anode/cathode stack?
 
Punx0r said:
If you can't get them out of the frame I would be tempted to very carefully prick them if it's possible to do so. It's just doing it without causing an internal short that could possibly provide the ignition source you're trying hard to avoid. So perhaps a non-conductive cocktail stick and go in at a shallow angle, if possible, in a location away from the anode/cathode stack?
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No offense intended, but this is terrible advise. I know this from first hand experience in trying it, I ended up burning myself in the process. Putting a hole in the pouch allows oxygen in and enables a fireball. The best bet is to first safely move the batteries to a location where fire will not harm anyone. Secondly, find a way to very slowly discharge the packs removing potential energy for future combustion. Only after they have been discharged should one attempt relieving the pressure.

-Jim
 
The problem is that they batteries can't be moved to an entirely safe location (in terms of property damage) because they are wedged in the bike. They also can't be discharged because the terminals have sheared off and immersing them in water to discharge means being able to remove them from the bike. Hence considering the riskier options. Pricking cells is definitely not a recommended action, but people have done it in the past to RC hobby cells (and carried on using them!). Regardless of what gas comes out or goes in the resulting hole, it should not ignite unless an ignition source is created, like a short in the cell. Obviously if someone were to decide this option was worth the risk in pursuing they should plan for the worst, wear appropriate safety gear and be ready for fire...
 
FWIW, it *is* possible to discharge the pack (while still on the scooter frame) by immersion in salt water, but it would require moving it quite some distance, for a trip down to the beach. ;) But this might also damage other things on the frame via corrosion later on, if not cleaned and dried.
 
Strip the bike down. Take the carcass to a plastic baby pool or cement mixing tub or old bath tube. Mix salt and water let soak. It will turn into a ulgy green soap with rusty bubbles. It's ugly but after some time they will find Zero. Don't know where the best place to dispose of the solution. Do it without an audience or children. It will be ugly.
 
999zip999 said:
Strip the bike down. Take the carcass to a plastic baby pool or cement mixing tub or old bath tube. Mix salt and water let soak. It will turn into a ulgy green soap with rusty bubbles. It's ugly but after some time they will find Zero. Don't know where the best place to dispose of the solution. Do it without an audience or children. It will be ugly.
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It does have many factors involved, but typically just gentle bubbling without drama if the tub is large. The salt solution left over isnt particularly hazardous. Maybe add some baking soda to shift pH to neutral and/or precip the solids and dump. Give solids with the batteries to recycler with the discharged cells.
 
At the moment we only have lead batt recycling here in CR, so I'm sure lithium batts are piling up from laptops and cell phones. I'll be sure to put all the waste with my other dead battery stockpile in a plastic lined box to save for the day when I can dispose of them properly.

I appreciate the info that over-charged cells will continue to decompose, so I can't just ignore it. I planned for today to be the day, but I unbelievably I forgot my multimeter and RC charger/discharger at the shop, which I planned to use to reduce energy as much as possible. I have been doing a daily inspection to make sure the pack shape isn't changing, which would indicate more gas buildup. I have the tub and salt ready, but my plan is a bit different. ie I'll start with getting the pack into plain water, and then add salt water solution slowly until something happen to keep the energy disharge process slow. Please let me know if that logic if flawed.

I did take a close look at everything today and got wiring like the lights and charger cords out of the way, since it ran across the top of the pack. I think duct tape across the top between the posts prevented a flameout due to a short.

I'm going to roll the dice, since I can't get the controllers and motor all the way off without cutting the pain in the a$$ and 4-6 hours to redo wiring harness, in hope that it will save time to get it running again. These days time is my most valuable resource. To me worst case is that this "safe chemistry" pack starts sputtering and spitting smoke as I'm pulling it out, and with my protective wear I'll have time to cut harnesses to get the good stuff safe.

The steel angle iron battery tray is held in place by 3 bolts, and right now the rear shock that the last cell bent itself against. The 2 side bolts will come off easily, and the last bolt holding the steel strap in front is oriented front to rear, so on the last turn of the nut I expect the pack and tray to spring forward even though the pack is current wedged in place. To prevent arcing shorts I'll add as much duct tape and plastic as possible between both the sheared off posts and tabs still bolted together and the cells with exposed live metal below, and the steel top tube above. I'll also add more bike innertube wrapping of the battery to the tray to hopefully prevent the pack from arching further, which could hinder removal and potentially start sparking.

I have my fingers and toes crossed that it's all uneventful till I start adding the concentrated salt water solution. Maybe I'll even be able to save some or all 4 cells at the front of the 14 cell string that aren't part of the 10s over-charged and puffed. Video will be recorded regardless.
 
It all starts when the salt hits the water. Meaning water alone is weak it's the salt. Good luck John.
Bubble bubble toil and trouble. It didn't happen if it's not on video.
 
I would a dissolved solution to pour over the top even if it's in the water. LFP you mean it's almost drinkable? Like what's the safety level.
 
Removal was thankfully uneventful. It seems that the overcharged puffed cells must have internally shorted at some point, but a low current short that didn't create heat too fast. I say that because the only cell that did anything after I added salt solution to the water was the fully charged cell (4.12v) attached at the end of the over-charged string. It went into the water too, because it was puffed...I assume from heat.

All now have hole punched in them with a nail on a stick and are bubbling away in the salt water solution.

I have some pics, but need one of my son's help loading to my PC.
 
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