Lithium Battery storage

[Bmi48219]

Wife’s friend woke up to smoke alarms last weekend. A fire had started in attached garage. FD arrived and put it out. Flame damage restricted to one side of garage, but smoke and soot damage throughout the house. The fire appears to have started where several lithium battery powered tools were stored on a wall. Batteries and tools are a lump of melted plastic and metal but nearby boxes were barely charred. Fed told them the residue / soot was toxic and a lot of possessions had to be discarded. The couple was fortunate as no injuries, but a major loss. Not sure if batteries were on charge at the time of fire.

[Winger Ed.]

Being on the charger is my guess.

Last month the company I used to work for had a fire that burned out about half the shop and offices.
It started from the shop's battery screw driver tools being on chargers over night, and one cooked off.
It probably doesn't matter, but they only use top of the line Milwaukees.

I've been thinking of putting mine in a metal box out in the driveway for charging them.

[uscra112]

The model airplane guys learned this bitter lesson 15-20 years ago. Never EVER leave a lithium battery on charge unless it's attended, or in a fireproof container. The model suppliers all sell boxes and fireproof bags to forestall this. I lost a whole plane that I was fond of once by not taking the battery out of it before charging. You'd be amazed at how fast balsa and doped paper covering burns!

[Thundarstick]

The model airplane guys learned this bitter lesson 15-20 years ago. Never EVER leave a lithium battery on charge unless it's attended, or in a fireproof container. The model suppliers all sell boxes and fireproof bags to forestall this. I lost a whole plane that I was fond of once by not taking the battery out of it before charging. You'd be amazed at how fast balsa and doped paper covering burns!

I use to fly RC, and witnessed one burn through a picnic table at the park when it shorted!

[MrHarmless]

The model airplane guys learned this bitter lesson 15-20 years ago. Never EVER leave a lithium battery on charge unless it's attended, or in a fireproof container. The model suppliers all sell boxes and fireproof bags to forestall this. I lost a whole plane that I was fond of once by not taking the battery out of it before charging. You'd be amazed at how fast balsa and doped paper covering burns!

Completely agree.

Lithium batteries are absolutely fantastic compared to NiCad and similar. Way more power for longer, but I hate the way power tools have implemented them.

Most power tool brand battery chargers are "Dumb". They use analog circuits to balance the voltage in each cell up to the maximum. This is fine if you're constantly using the tool, but most Lithium batteries should be stored at ~80 percent of their max voltage to maintain their service life. They're (The chargers) also much more susceptible to physical disruption like shorts or "an excess of disagreement between the 1's and 0's", and over time potentially unbalancing the cells, which causes internal breakdown, and in extreme cases lead to cell rupture, which is bad because lithium and air don't get along, especially when the hydrogen produced when they break down chemically enters the fray.

Most lithium cells are rated for a nominal voltage of 3.7 volts, but maximum is generally 4.2 volts, and over time that'll degrade the life of the battery if you just let them sit. Anybody that's used LiPo batteries for RC or Airsoft know about relatively inexpensive "Smart" chargers that you can program to charge for storage or general use. Wish more power tool chargers had that option.

[georgerkahn]

Wife’s friend woke up to smoke alarms last weekend. A fire had started in attached garage. FD arrived and put it out. Flame damage restricted to one side of garage, but smoke and soot damage throughout the house. The fire appears to have started where several lithium battery powered tools were stored on a wall. Batteries and tools are a lump of melted plastic and metal but nearby boxes were barely charred. Fed told them the residue / soot was toxic and a lot of possessions had to be discarded. The couple was fortunate as no injuries, but a major loss. Not sure if batteries were on charge at the time of fire.

A friend rang me several months back with his statement re the "goodness" of his wife's cigarette smoking habit, as it no doubt saved their residence, if not, too, their lives! "Huh?" I asked... It turns out the wife ran out of smokes and asked hubby to fetch a pack she had in her garaged car. When he entered the garage he said it did not take too long before his eyes started burning and a real bad odor was present. Walking to the rear of garage, to his workbench, he noted a Lithium drill battery plugged into a wall-wart charger that was quite bulged, all around, and "hotter then hell". He unplugged it and -- after burning his fingers -- moved it to concrete curb at road-end of their drive.
Interestingly, he voiced that he had used the drill earlier in the day, and it had dropped from shelf on the 6' step ladder he had been using to the floor -- postulating that perhaps the fall to floor damaged the battery?
Anyhoos -- here's a site on Li batteries I found useful... From MIT.
https://ehs.mit.edu/lab-research-program/lithium-ion-battery-safety/

[uscra112]

^^^ All true ^^^ Accurate, reliable balancing is absolutely essential. Component failure in the balancing circuits is guaranteed disaster. Some power tools use lithium-IRON cells, which I've read are more tolerant.

But think on Teslas, which have a thousand cells or more, each one of which has to be monitored separately. Probability of component failure in a thousand monitoring circuits...???

I'm not building or flying anymore, due to disability, but I note that my last RC charger not only monitors each cell, it charges each individual cell separately if the pack is wired for it. Do power tool chargers do that? I doubt it. If they do the circuitry would have to be inside the battery pack. I've never seen one with more than the minimum two contacts.

[Handloader109]

Yep, most probably caused a short somewhere. I have gotten to the habit of charging and then cutting off the whole bank with a powerstrip. What really would be better would be get one of the Christmas light remotes that have 2 or 4 hour timers. Put the charger on that....

Sent from my SM-S908U using Tapatalk

[uscra112]

What happens is that a cell shorts internally. The current dump is very large and very sudden. Lots of heat, and the electrolyte is flammable.

A timer is an excellent idea.

[clearwater]

Water is also an issue with lithium cells. Local waste to energy plant burns trash to make electricity and has fires in the pre-burn debris from time to time when lithium cells are dropped, crushed or have liquid come in contact with them. They have a special drop off for batteries to help avoid this.

[uscra112]

Also true. Water can short a cell externally, creating a lot of heat. We made it a point to soak cells to be discarded in salt water for a day to drain them down to a 100% inert state before they went in the trash.

[imashooter2]

How many millions of lithium batteries charge every day in the US? Phones, laptops, tools, appliances… I wouldn’t doubt that the number makes it into billions. That there is an occasional fire isn’t very surprising. You all can do what you like, but I’m still going to charge my phone indoors without watching it every moment.

[kerplode]

^^^ All true ^^^ Accurate, reliable balancing is absolutely essential. Component failure in the balancing circuits is guaranteed disaster. Some power tools use lithium-IRON cells, which I've read are more tolerant.

That chemistry is Lithium Ferro-Phosphate (LiFePO4). It doesn't have the energy density or performance of other Lithium cell chemistries, but it is indeed safer.



But think on Teslas, which have a thousand cells or more, each one of which has to be monitored separately. Probability of component failure in a thousand monitoring circuits...???


The Tesla pack is composed of parallel and series elements. Many individual small cells (essentially 18650's) are wired in parallel blocks, then several of those are connected in series. The balancing is done across the parallel elements, since they essentially look like a really big individual cell. Each little cell is balanced when the parallel element is assembled at the factory, but after that, they run as a group.

Each cell in the parallel group is bonded to the common conductor with what is essentially a fuse, so if one cell malfunctions and shorts or whatever, it's just fused out and that parallel block loses a bit of capacity, but the rest soldier on.

Tesla has the most advanced battery management hardware in the industry, but their packs still occasionally go high-order and burn down someone's house. Something to think about when you buy a cheap Li+ tool. Anyway, last time I talked about Tesla battery tech here, some dude got his panties in a bunch, so we'll leave it at that.



I'm not building or flying anymore, due to disability, but I note that my last RC charger not only monitors each cell, it charges each individual cell separately if the pack is wired for it. Do power tool chargers do that? I doubt it. If they do the circuitry would have to be inside the battery pack. I've never seen one with more than the minimum two contacts.

Dewalt 20V Max packs have 8 contacts. B+ and B- for the battery load, Temperature output, an ID pin to tell the charger what the pack is, and C1 through C4, which are the intermediate nodes in the series string of cells. This gives the charger the ability to balance the series elements individually.

[bimus]

After reading this I made a change in the shop
Over the bench I plugged in a power strip that has a switch and plugged in to the strip is the drill charger over head light and the radio .When I leave the shop I always turn off the light and radio and now turning off the switch on the power strip it will turn off the power to the battery charger also .

[kerplode]

How many millions of lithium batteries charge every day in the US? Phones, laptops, tools, appliances… I wouldn’t doubt that the number makes it into billions. That there is an occasional fire isn’t very surprising. You all can do what you like, but I’m still going to charge my phone indoors without watching it every moment.

Phones are significantly safer. I have no issue leaving a phone to charge unattended.

I don't leave tool packs and similar alone, though...

[uscra112]

Phones have only one cell in them, so there's no balancing issue.

[kerplode]

It's perfectly possible to blow up a single cell.

Phones are safer because they have better charge/discharge management hardware than cheap tool packs.

[uscra112]

Sure, but charge management is a whole lot easier. Some years ago there was a rash of phone fires resulting from women putting their phones under their pillows while charging. Overheat ensued. Phone mfgrs. had to add another idiot-proofing feature to the product.

A huge proportion of tool packs are coming from China without adequate QC on the part of the USA marketers. Don't need to explain further, do I? I no longer buy anything to do with batteries or chargers via Amazon or evilBay. I swear half the stuff on offer is Chinese counterfeit.

[kerplode]

Sure, but charge management is a whole lot easier. Some years ago there was a rash of phone fires resulting from women putting their phones under their pillows while charging. Overheat ensued. Phone mfgrs. had to add another idiot-proofing feature to the product.

A huge proportion of tool packs are coming from China without adequate QC on the part of the USA marketers. Don't need to explain further, do I? I no longer buy anything to do with batteries or chargers via Amazon or evilBay. I swear half the stuff on offer is Chinese counterfeit.

Yup...I totally agree!

[MaryB]

^^^ All true ^^^ Accurate, reliable balancing is absolutely essential. Component failure in the balancing circuits is guaranteed disaster. Some power tools use lithium-IRON cells, which I've read are more tolerant.

But think on Teslas, which have a thousand cells or more, each one of which has to be monitored separately. Probability of component failure in a thousand monitoring circuits...???

I'm not building or flying anymore, due to disability, but I note that my last RC charger not only monitors each cell, it charges each individual cell separately if the pack is wired for it. Do power tool chargers do that? I doubt it. If they do the circuitry would have to be inside the battery pack. I've never seen one with more than the minimum two contacts.

Good tools have an equalizing board inside each pack.

[MaryB]

It's perfectly possible to blow up a single cell.

Phones are safer because they have better charge/discharge management hardware than cheap tool packs.

Phone flat pack batteries are a different chemistry, one that doesn't start on fire as easily as the 18650 cells in tool battery packs

[uscra112]

Phones use lithium polymer cells, which are even more prone to failures than the hard shell 18650. Ask me how I know.

[MaryB]

I NEVER charge a lithium battery unless I am monitoring it. Because of my bad back I have to get up and stretch every 2 hours or so so I walk over to whatever is charging and feel the pack to make sure it has no hot spots. Had a cheap Chinese tool pack start to overheat last week. Caught it in time to unplug it. Buried it in a bucket of sand I keep next to my repair bench where I replace phone batteries. Sometime a battery will short as you wedge it out(they are glued in!) and start to burn. Into the sand and bury it. Smothers the fire.

Tesla started on fire 7 miles from me. It burned so hot that the glass and rims melted into the pavement. The remains of the car fit in a bobcat bucket... rest burned/melted. Couldn't pay me to drive a lithium battery powered car! Toxic waste dumps on wheels!

[trebor44]

Extremely helpful info, especially the link to EHS.mit docs! Always had to wonder about the un-attended charging since the BLM office in Challis burned down a couple of years ago. Thanks to all who contributed.