Battery Fires

[Woosh]

If this level of scrutiny had been applied to wiring our houses to the electric grid or piping explosive gas into our homes, we would all be without electric power and heating.



Many systems and products are prone to dangerous abuse.
Three men were arrested after the incident referenced above and charged with manslaughter.

I tentatively agree with you but there is a fundamental difference in maturity of the products.we don't expect our wiring to burst into flames even if we accidentally drill into it. I have highlighted many times the risks of battery fires. The root of the problem is in the immature technology of NCM batteries, aggravated by the secondary market in remarking rejected cells and consumers greediness, always want to buy the cheapest. We now know how to make batteries that last 75+ years but they don't yet have the capacity to weight ratio that we want on our bikes.

 

[Ghost1951]

I tentatively agree with you but there is a fundamental difference in maturity of the products.we don't expect our wiring to burst into flames even if we accidentally drill into it. I have highlighted many times the risks of battery fires. The root of the problem is in the immature technology of NCM batteries, aggravated by the secondary market in remarking rejected cells and consumers greediness, always want to buy the cheapest. We now know how to make batteries that last 75+ years but they don't yet have the capacity to weight ratio that we want on our bikes.

Some people do some REALLY stupid things. The people who blew up that block of houses and killed I think three people will likely have been by passing the gas meter. This happens surprisingly frequently. People electrocute themselves. You really can't do that unless you do something VERY stupid.

I knew and understood the consequences of messing with gas and electricity by the time I was four years old. We actually had gas taps that I could get at at that age and could have turned on with no device to stop the house filling with town gas which was about 50% - 60% hydrogen.

Were there problems caused by idiots then? Yes - that is why parents like mine made SURE that I knew never to meddle with gas taps. It was also highly poisonous too. It had about 30% carbon monoxide in it and was a favourite way to commit suicide at the time.

Nobody here has ever had a battery fire. The numbers of battery fires in absolute terms are very small in comparison to the numbers of batteries in use.


EDIT:

i tried to look up how many people are admitted to hospital as a result of mishandling petrol. There is no data online, but I do know that a surprising number of people have accidents with petrol.They tip it onto barbecues and I know someone who poured an egg cup full into his wood burner and was burned by the exploding flame which gushed out of the thing with a bang right into his face.

 

[Ghost1951]

I found this table on the Direct Line website listing fires caused by electrical appliances. No ebikes. Lots and lots of ordinary appliances.

Ovens need to be banned or at the very least very highly regulated - 6609 of them went up in flames and caused an insurance claim. My GOD!!! Who would have thought it and no House of Commons Inquiry into that.

This fussing about is disproportionate and all total ******.

Appliance	2019/20	2023/24	Percentage Increase / decrease
Battery charger	60	122	103
Other cooking appliance (inc air fryers)	234	305	30
Electric blanket	25	31	24
Deep fat fryer	186	201	8
Washer dryer	69	73	6
Hair dryer	48	47	-2
Extractor fan	183	170	-7
Microwave	923	803	-13
Tumble dryer	667	567	-15
Cooker / oven	8,018	6,609	-18
Vacuum cleaner	43	35	-19
Washing machine	627	480	-23
Iron	36	26	-28
Grill / toaster	1,370	941	-31
Dishwasher	194	133	-31
Fridge / freezer	216	147	-32
TV	32	19	-41
PC equipment	50	29	-42

Source: Churchill home Insurance 2024

 

[Woosh]

I found this table on the Direct Line website listing fires caused by electrical appliances. No ebikes. Lots and lots of ordinary appliances.

Ovens need to be banned or at the very least very highly regulated - 6609 of them went up in flames and caused an insurance claim. My GOD!!! Who would have thought it and no House of Commons Inquiry into that.

This fussing about is disproportionate and all total ******.

Appliance	2019/20	2023/24	Percentage Increase / decrease
Battery charger	60	122	103
Other cooking appliance (inc air fryers)	234	305	30
Electric blanket	25	31	24
Deep fat fryer	186	201	8
Washer dryer	69	73	6
Hair dryer	48	47	-2
Extractor fan	183	170	-7
Microwave	923	803	-13
Tumble dryer	667	567	-15
Cooker / oven	8,018	6,609	-18
Vacuum cleaner	43	35	-19
Washing machine	627	480	-23
Iron	36	26	-28
Grill / toaster	1,370	941	-31
Dishwasher	194	133	-31
Fridge / freezer	216	147	-32
TV	32	19	-41
PC equipment	50	29	-42

Source: Churchill home Insurance 2024

Matured technology TVs, PCs and laptops don't set fire to your homes, chargers and air fryers aren't as safe.
See 122 battery chargers, 103% increase, 305 fryers, 30% increase.

 

[Ghost1951]

Matured technology TVs, PCs and laptops don't set fire to your homes, chargers and air fryers aren't as safe.
See 122 battery chargers, 103% increase, 305 fryers, 30% increase.

The air fryer craze of last year meant that there were very very many more of them. You'd expect that rise when millions of a product get sold.

Even I bought one.Great for knocking up a quick egg and chips. I put the eggs in a recycled pie base. Chuck the eggs in for the last six minutes of the chip cooking. I doubt I had ever had egg and chips for forty years until I got the air fryer. £26 at Lidle.

Bargain.

It is likely that air fryer fires were caused by stupid abuse, like blocking the exhaust air vent with a towel. There is no obvious reason why one would catch fire if used according to directions, or sustain combustion to the extent that required fire service involvement. Maybe some idiots half fill them with oil. And this is my key point - idiots cause dangerous things to happen that wiser heads would see a mile off - such as charging a 36 volt battery with a 56 volt charger.

Who knew that was a problem?

Everyone who doesn't need a 'zoo keeper' to take them for a walk in the park.

 

[eas2lv]

While it remains legal to do so, I'll get aound to assembling my always-on if above Low Voltage Cutoff battery overheat alarm, I think I might have all the bits.

Motivated by this (and the related thread) I too implemented an external temperature monitoring + alarm.

But, being unsure how effective such a system would be, I did a quick and dirty simulation of heat transfer from the center of a battery pack to outside assuming one of the cells develop a runaway event and it then propagates into neighbouring cells. The results are sobering unless I made a mistake: it does take several minutes for the event to spread, but the temperature of outer cells remain rather low (close to room temperature) for a long time. The temperature of the enclosure rose by 10 to 20C only when the runaway had spread to a few cells, and from that point it rose rapidly to be useful for an alarm system.

I think one has to tap into the temperature signal of the BMS and hope that there are enough temperature sensors distributed over the pack to detect the failure much earlier.

Though I might have made a mistake, I found a more sophisticated simulation online with similar results:
/https://www.comsol.com/model/download/1345961/models.battery.thermal_runaway_propagation.pdf

 

[guerney]

Motivated by this (and the related thread) I too implemented an external temperature monitoring + alarm.

But, being unsure how effective such a system would be, I did a quick and dirty simulation of heat transfer from the center of a battery pack to outside assuming one of the cells develop a runaway event and it then propagates into neighbouring cells. The results are sobering unless I made a mistake: it does take several minutes for the event to spread, but the temperature of outer cells remain rather low (close to room temperature) for a long time. The temperature of the enclosure rose by 10 to 20C only when the runaway had spread to a few cells, and from that point it rose rapidly to be useful for an alarm system.

I think one has to tap into the temperature signal of the BMS and hope that there are enough temperature sensors distributed over the pack to detect the failure much earlier.

Though I might have made a mistake, I found a more sophisticated simulation online with similar results:
/https://www.comsol.com/model/download/1345961/models.battery.thermal_runaway_propagation.pdf

This small collection of gizmos:

https://www.pedelecs.co.uk/forum/threads/home-ruination-by-ebike-battery-fire-expulserating-preterminator%E2%84%A2%C2%AE%C2%A9%E2%84%A0.46934/

...only needs to buy me about 30 seconds advance warning, hopefully a minute or so, so I can expulserate my soon to be explodey battery via my window, or in the case of the on-battery version jump off my bike and flee, or break a train window to expulserate it via, not to prevent thermal runaway. Judging by the speed temeprature rises while charging, I believe it will buy me sufficient time, while charging or resting in storage at least. It's a heck of a lot better than waiting for ignitable smoke to set off a smoke alarm, at which point it's far far too late to do anything but kiss your home and belongings goodbye and run away as fast as possible. You lot can do what you like.

 

[eas2lv]

My point was that the temperature sensor has to be placed inside the pack. It may be be too late if you wait for the temperature on the outer surface of the pack enclosure to rise even by 10C.

 

[Ghost1951]

If anyone is concerned about fire risk, why not get rid of the sensitive chemistry and go LiFePo4. This chemistry is vastly less likely to get upset and when it does, perhaps through penetrating injury it does not result in fire. It is much safer all round and is supposed to last longer in its modern iterations.

Of course it has lower energy density, so you will need a larger and heavier pack, but for an ebike - the assistance could be said to counteract a bit of extra weight. If you are concerned about fire risk, this might be the way to go.

I think you might have to make your own pack though, but cells with screw terminals are available in good capacities.

Lithium 3.2v 32700 6Ah LiFePO4 Rechargeable battery cell Male-Female M4 | eBay

Battery Size Battery Type Cycle Life >2500 cycles @1C to 80%DOD. 60A/10C, 3s. 1C at CC/CV.

www.ebay.co.uk

 

[guerney]

My point was that the temperature sensor has to be placed inside the pack. It may be be too late if you wait for the temperature on the outer surface of the pack enclosure to rise even by 10C.

I'm not so sure, and I'm not sacrificing my battery or cell-less enclosure prematurely to find out. I suppose I could buy an emoty battery enclosure and place probes both inside and out to see how fast temperature rises with a heater placed within, but I can't be bothered. I'm that sure.

The mobile version could have a heat probe placed within the enclosure - I'd only assemble and install the gizmo if my worry about transporting my ebike battery on trains becomes overwhelming. Currently, it isn't.

 

[Ghost1951]

Safety is enhanced if you treat the battery with caution.

• Don't charge the battery unattended at night
• Use a slow charger of correct voltage
• Periodically check that the charger voltage is still correct (multi meter)
• Don't draw currents beyond the cell capability by tampering with max current settings
• Keep the battery enclosure waterproof to protect against BMS failure
• Make sure the battery is safely constructed and proofed against chafing - shorts can happen in badly constructed batteries through cell wrap chafing
• Periodically open the battery and inspect it for deterioration or water ingress

 

[Ghost1951]

My point was that the temperature sensor has to be placed inside the pack. It may be be too late if you wait for the temperature on the outer surface of the pack enclosure to rise even by 10C.

The problem here is that in a chunky battery pack the temperature sensor might be quite a way from a cell which has heated up too much and may not have been able to detect the problem because at that point in time the sensor is still cool while a particular cell is about to go into melt down.

I think in order to be sure you would need a number of sensors in the pack - evenly distributed.

 

[guerney]

Battery case surface temperature rises fast enough via air convection within the case, for the purposes of flinging out of the window to prevent home conflagration. I suggest you do your own measurements:

 

[Woosh]

If anyone is concerned about fire risk, why not get rid of the sensitive chemistry and go LiFePo4.

LiFePO4 has lower self heating rate compared to NMC but that's not enough to prevent thermal runaway and still suffers from oxygen evolution due to humidity and SEI (solid electrolyte interphase) deposition on the anode. Most of the current efforts go on to large EV and storage batteries, we still have no new choice for e-bike batteries other than NMC. Among the improvements, we may have 3D printed electrodes, temperature sensitive separator, adding Li2ZrF6 to the electrolyte for example.

 

[eas2lv]

Battery case surface temperature rises fast enough via air convection within the case, for the purposes of flinging out of the window to prevent home conflagration. I suggest you do your own measurements:

This does not show the lag between a thermal event at some point inside the pack and when that reflects in temperature at the surface. As per my simulation and what I saw online, there is a lag of minutes leaving too little time to act on an alarm. One needs multiple sensors inside the pack distributed evenly.
Not saying your gizmo is useless.

 

[guerney]

This does not show the lag between a thermal event at some point inside the pack and when that reflects in temperature at the surface. As per my simulation and what I saw online, there is a lag of minutes leaving too little time to act on an alarm. One needs multiple sensors inside the pack distributed evenly.
Not saying your gizmo is useless.

Even if the alarm didn't sound before enough ignitable toxic smoke escaped the case to set off the smoke alarm, I believe it'd sound well before the smoke alarm did. Any additional seconds or minutes of forewarning is welcome.

I was intending to do a much better job of recording temperature over time yesterday, but I was in a rush to charge my ebike battery, and there didn't seem much interest about my gizmo's thread, thought it'd further bore people. But I will do so at some point. Prepare to be bored.

Simulation is all well and good, but experiment is necessary. I really didn't think there would be any externally detectable temperature change - cheap and easy suited me down to a tee, so I decided to try it, and there is. I suppose you could take a downtube battery top cover, plonk a temperature probe on the top externally as I have, and quickly place it over something something requisitely hot, making sure hot air is trapped inside, and see how fast externally measured temperature changes. I tested using a hairdryer in the very long and boring badly edited promotional video. You're free to place multiple sensors within the pack, rather like the UL 2849 safety standard - that would be much better of course, and I look forward to seeing the results. I prefer easy cheap and cheerful, and that's why I married my wife.

 

[lenny]

China Encourages Citizens to Swap ‘Old Lithium E-Bikes’ for New Lead-Acid Models

China Encourages Citizens To Swap 'Old Lithium E-Bikes' For New Lead-Acid Models

In a surprising policy shift, China is urging citizens to trade in their lithium-ion electric bikes for models powered by sealed lead-acid batteries (SLAs). While e-bikes are a key mode of transportation in urban China, safety concerns over lithium-ion batteries have led the government to...

greekcitytimes.com

 

[Woosh]

China Encourages Citizens to Swap ‘Old Lithium E-Bikes’ for New Lead-Acid Models

It's good that they are not obsessed with people using the throttle. E-bikes are about the best and safest form of simple, non polluting cheap transports.