When a Lithium ion cell explodes how much damage can it do? :)

[mxlemming]

I have failed to make batteries die from over current/short circuit.

A while ago i put a jump lead clamp across the ends of an 18650 and... Nothing really happened. It just got hot.

Where they all seem to go wrong is when they're over charged. It realistically takes a significant over charge to blow a cell but it's actually very easy with series parallel packs to accidentally create this fault. All you need is for one of the cells in a P group to come unsoldered, and with a16,20...s whatever... pack there a lot of spare voltage available from the charger.

At this point, you have a p group with fewer cells in it so the remaining ones charge much faster. If you have a BMS and it's still connected to the ones charging, it'll shut down. If it's connected to the cell that's... disconnected... The fault is silent until it blows.

That's why they usually blow while charging. Something shakes the connections loose.

For this reason, I charge mine in my concrete garage with 1970s asbestos roof and always check the cell voltages on the BMS 15 minutes in to see they're all going up equally.

 

[Cyclomania]

I have gotten some cells now. My battery charger looks like the picture. WIth this I should dicharge the cells to the lowest possible voltage correct? And then they would be less likely to cause an explosion/fire?

How are these dischargers used? Just put the cells in there and discharge them with a button somehow?

 

[liveforphysics]

All battery cells are like a strike anywhere match giving the right circumstances they all catch on fire explode cause multiple fires and cells to explode in there path all kinds of ways.
Lightning in a box.
Luke how do you build your battery packs what sales do you use how do you connect them what are the biggest no-nos.

Our website has a handful of podcasts that mention some of these topics. Condensed version is I like to wire bond my cell interconnects, and then pot them in a polymer with intumescent properties loaded with a low activation temperature (~105degC) thermal decomposition endothermic filler in the potting material. If you get your spacing and materials right for the given cell type, you can eat thermal runaway events under the worst of situations without spreading cell to cell or needing any external firefighting efforts.

The cells themselves generate byproducts >1800degC, and the electrically coupled plasma temperatures while tricky to measure are >5,500degC. We do a lot of thermal runaway ARC calorimetry, and impressively cells beat solid rocket motor propellant just in heating value per mass alone. Myself and friends in the business have all been injured and scared by batteries, the extra sad effects are the lung damage so wear good PPE to not breathe TR byproducts if you don't have a scrubbed test chamber.

 

[liveforphysics]

Also, on the topic of what it takes for cells to explode, our lab has never failed to initiate thermal runaway on any type of cell we were requested to test.

We do fiber optic laser initiation, nail penetration, hot-wire, hot-nail, molten salt bridge, all types of electrical stress initiation, and to date every cell has a reliable method in which the energy it stores can be released into itself. This is handly because to get the data for the Joules of energy released and gas pressure curves and gas species, its essential to be able to trigger the TR event while the cell is inside the calorimeter.

 

[liveforphysics]

I have gotten some cells now. My battery charger looks like the picture. WIth this I should dicharge the cells to the lowest possible voltage correct? And then they would be less likely to cause an explosion/fire?

How are these dischargers used? Just put the cells in there and discharge them with a button somehow?

You realize whats shown in that image is a spot welder not a battery charger right?

 

[amberwolf]

I have gotten some cells now. My battery charger looks like the picture.
WIth this I should dicharge the cells to the lowest possible voltage correct? And then they would be less likely to cause an explosion/fire?

How are these dischargers used? Just put the cells in there and discharge them with a button somehow?

I don't see anything that looks like a typical charger or a discharger.

What I see in the picture you posted (which I've attached to this post in case the original is lost or changed) looks more like a spotwelder with a foot pedal control.

As for how any particular discharger would be used, you would need to read the manual for it to find out how the specific one you have works. Usage may be dependent on the cell type you are discharging as well, and what it's starting state-of-charge is.

As for the voltage to discharge to, you would need to check the spec sheet for the cell as to what it's lowest safe voltage is, unless you are discharging them to zero for disposal.

 

[Cyclomania]

Ah crap wrong picture. I was uploading it quickly after training. So it came up a bit hasty. Sorry haha I have changed it to the right picture I was intending to upload now.

The one I uploaded first was the spot welder. But after I changed the picture you can see the discharger/cycler there now.

I am going to start a battery building thread when the BMS arrives. But first I am going to learn how to use the discharger/cycler and so on. So I am not doing anything wrong.

I am currently reading a book by Micah Toll on building batteries. I have most of the stuff I need now I think except for the bms.

The case I am going to use to build the battery is a Polly DP-9 52volt looking like below. The nickelstrip is also like the picture.
The cells are the ones below the top image, and are of the HG2-kind.

 

[Cyclomania]

What do you think? These are the right pictures.