Battery charging and fires

[old mart]

Remember that spate of fires caused by a new Samsung mobile phone? It cost the company millions as they ended up withdrawing the whole model.

[psomero]

It takes electronic technology to properly control the charge of batteries. Particularly important for LI batteries that become unstable if over charged, allowed to go below a threshold of discharge, or are physically damaged. In videos of LI battery fires, they aren't passively burning in place. They tend to "burst" and toss burning matter around.

I would be as much or more concerned with the design and quality of the components used in the controller boards contained in the chargers. Failures there can cause an otherwise stable LI battery to become unstable.

You are correct that handling outside of a fairly narrow range of operating parameters can cause catastrophic failure on most lithium secondary cells (rechargeables).

The resulting fire is usually not accompanied with shrapnel or burning matter, but is really a hot jet of flames, superheated flammable electrolyte, and the decomposition products of the separator. It's just a hotass flame and toxic smoke (fluoropolymers in the separators or outer wrap sometimes), but usually no projectiles.

In my experience, it is usually dodgy chargers in which there were unacceptable quality corners or BOM substitutions made at the factory in Asia, or dumb operator error (like someone plugging in a pack backwards because the connectors aren't properly protected or polarized) that are the main culprits in pack failure. I've been working in EVs, almost exclusively with aggressive lithium chemistries, for a long time.

The sketchiest thing is usually an offbrand knockoff of an offbrand generic BMS or charger, someone cut a corner and went from a precision ±0.5% discrete component to a cheaper ordinary ±10% alternative, and the cells go out of range on charge current or charge termination voltage.

[OaklandGB]

Well I am certainly no expert, and have only a rudimentary knowledge on LI cells from reading accident reports and a few tech papers. Your comments are appreciated and hope will be taken into consideration by anyone embarking upon a home shop LI battery project.

[Bob Engelhardt]

I have a shop outlet that's switched with the lights. I could put my chargers on that & they would be available when I need them.

[I make chips]

Lipos are indeed scary. Just go on utube and search 18650 battery fires. My god those things have a **** ton of energy in them and go up with a lot of force.
18650 cells are the most common cells used in power tools (cheap to manufacture) and also the Tesla cars. With umpteen thousand of them in a Tesla it will be quite the toxic and scary conflagration when they light off with their propensity for a cascading failure.

My kid is a fire fighter and they will only squirt an electric car fire with a C02 extinguisher.
After that they have to let it go critical and burn to the ground as they keep a large distance from the fumes. If someone is trapped in the car sorry to say they likely will be incinerated or suffocated by the highly toxic fumes.

[psomero]

Remember that spate of fires caused by a new Samsung mobile phone? It cost the company millions as they ended up withdrawing the whole model.

that was just stupid mechanical design. They did something which compromised the structural integrity of the cell separator, and then combined with fancy whizbang "modern" styling of gluing the battery into the swoopy curved phone, it caused stresses on the cell that one shall not impart if they don't want a fire.

a pouch type cell is a whole other beast relative to the can cells that are most often utilized in power tools. can cells are a jelly roll of layers of active material that gets stuffed into a drawn steel can. it's basically idiot proof, unless you crush the can. a pouch cell, on the other hand, can be stabbed with a tool or pinched and cause an internal short leading to a guaranteed near-instantaneous fire.

[psomero]

After that they have to let it go critical and burn to the ground as they keep a large distance from the fumes. If someone is trapped in the car sorry to say they likely will be incinerated
or suffocated by the highly toxic fumes.

name one instance of this happening in a crash that wouldn't have otherwise incapacitated or killed the occupants regardless of powertrain type. the time scale over which the energy is released is much longer, which affords the potential casualties time to flee.

batteries sizzle, smoke, and then go. you have time to run. gasoline vapor is explosive and there is one vessel which contains all of the high energy material, wheras batteries are thousands of tiny little cells and you have to have a thermal runaway event and multiple cascading ruptures before all the energy is released.

[Joel]

Yep, likely dead regardless.

Vehicle fires very seldom result in explosions in any problematic way (except on TV).
Electrics and hybrids get attacked similarly to other vehicle fires, with one exception being a recommendation to use a master stream (generally ignored due to practicality, I imagine).

If you are fighting ANY vehicle fire without full PPE and SCBA, you are an idiot and are surely going against your departments SOP's (not that idiots don't do it all the time).
A fire with a magnesium component is a somewhat common situation, and is likely to cause an increased level of drama.

[J Tiers]

name one instance of this happening in a crash that wouldn't have otherwise incapacitated or killed the occupants regardless of powertrain type. the time scale over which the energy is released is much longer, which affords the potential casualties time to flee.

batteries sizzle, smoke, and then go. you have time to run. gasoline vapor is explosive and there is one vessel which contains all of the high energy material, wheras batteries are thousands of tiny little cells and you have to have a thermal runaway event and multiple cascading ruptures before all the energy is released.

Don't be concerned about "I make chips"....... He is convinced that wind turbines are why Texas has big problems right now. He hates ALL "green" stuff, including the (coal powered) electric cars.

[JRouche]

18650 cells are the most common cells used in power tools (cheap to manufacture) and also the Tesla cars. With umpteen thousand of them in a Tesla it will be quite the toxic and scary conflagration when they light off with their propensity for a cascading failure.

When I read that a while back it surprised me. I thought they would have produced a better cell. They litteraly have thousands of the 18650s in them. I found that out while looking for some cells. I didnt buy any of those. No way.

They are on ebay by the tone if you need some. JR

P.S> Tell yer Son I like what he is doing and I am proud of him and what my fire fighting instructor told me (welding also).

Keep your face out of the fumes! JR

[Fasttrack]

If you are really concerned about it you can built a metal enclosure with a door and put a thermal link on it (like those on parts washers and old school fire doors) so if it gets hot it slams shut. However I would have to question the effectiveness as I've seen a lithium battery fire demonstrated and its pretty much like a thermite charge. If a cell burns for any reason it gets hot and cooks off the next cell and keeps repeating.

We do a lot of battery technology development at work and have a whole line of specialty Li batteries for the DoD. This often requires extensive testing over a very wide temperature range. Consequently, we've had more than our fair share of battery fires. All the battery charging / testing work is now done in boxes with thermal links in the lids. The bottom is filled with something like 6" of sand. We've had a few go up in these boxes but they've remained contained and the outside of the box relatively cool.

One thing to point out is that the cord going into / out of the box can pass fire the surrounding area. We use high temperature leads that wrapped in fiberglass insulation instead of something like an ordinary PVC insulation so there is little chance of fire spreading along the cord to nearby areas.

[JRouche]

Oh, and if there are any cavemen, like myself out there that still have a landline (telephone) you might have Li'ons roaming your house at night. Meaning although my landline has a corded phone attached it also has some cordless phones attached (cordless is not wireless, weird). My cordless unit has a base unit and three satellites. Each of those satellites has a lil lion inside charging away all day and night waiting to bite Oh My!!! JR

[J Tiers]

................

One thing to point out is that the cord going into / out of the box can pass fire the surrounding area. We use high temperature leads that wrapped in fiberglass insulation instead of something like an ordinary PVC insulation so there is little chance of fire spreading along the cord to nearby areas.

Just one suggestion that may do much for the entire issue.....


Arc fault detector outlets.

That should take care of the "fuse" running from the charger to the wall (the cord).

My father recalls seeing an arcing cord run the fire right across 30' of open ground as it fried the insulation, but never developed enough current to pop the fuse. They unplugged it. That was when they were trying to start the Franklin, and it was cold out. Would not crank over until warmed, but the cord was not big enough for the heater.

[OaklandGB]

I would guess that anyone who dies from fire inside a vehicle has probably already been disabled or rendered unconscious by the accident. Fires spread relatively slowing in most cases.

On the EV front, it looks like Netherlands fire fighters have adopted a "safe", literally a steel tank in which to submerge smoldering EVs.