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Ebike News
- Thread starter lenny
- Start date
I love the explanation for why it caught fire. "It went into thermal runaway" as if that's normal for a vehicle. They might as well have said the reason it burned to a cinder was that flames started coming out of it.
How can a car that's peacefully sitting on a driveway randomly catch fire? Can anybody make some rational explanation because when I did physics at school, they told me that you needed some sort of ignition or electricity flowing?
Of course I'm sure, I live here. Read my post. Your examples are both in flat central Croydon where there and in North Croydon quite a few e-bikes are used for meal deliveries. Indeed I saw two Saturday midday as I drove away from a scan appointment at Croydon University Hospital in London Road, North End.
The bulk of this borough is in the too hilly south, as I posted, where all the fast food deliveries are done with i.c. mopeds, the hills and distances too much for e-bikes.
Its an irony that e-bikes are most popular where it's flat, such as our Eastern Counties, the Somerset levels and the Netherlands and Denmark. Here in the hilly North Downs I almost always seemed to be the only one riding them.
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As you know, common Li-ion cells can and sometimes do self ignite through dendrite crystals forming and piercing internal insulation, creating shorts. It just needs one defective cell out of the thousands that are often used in an e-car battery to create a runaway uncontrollable fire.
That is why i drive a Nissan Leaf which only uses 192 very large cells which are very different from the common consumer cells that others use, and very safe in consequence:
"The 40 kWh Nissan Leaf battery uses 192 lithium-ion cells , each with a capacity of 135 Ah and a nominal voltage of 3.75 volts. The battery is made up of 24 modules, each containing 8 cells. The battery's nominal voltage is 360 volts.
The Nissan Leaf's battery is made of lithium manganese oxide (LiMn2O2) with a positive Ni-Co-Mn electrode material. This material has a layered structure that allows the battery to store many lithium ions, increasing its storage capacity. The battery also uses rolled structure cells, which have a simple structure and high cooling performance, saving space and reducing the overall size of the battery pack.
The Nissan Leaf was the first mass-produced electric vehicle (EV) to use lithium-ion batteries. The Automotive Energy Supply Corporation (AESC), a joint venture between Nissan and Tokin Corporation, manufactures the lithium ion batteries for the Nissan Leaf."
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Since the car had not been used for ten hours and it was not on charge, I am supposing that there must have been a fault in one of the battery cells, such as the development of a short circuit - perhaps from copper deposits migrating from the anode backing layer, and breaching the separation between the anode and cathode material. There may have been a fault in the integrity of the insulating material - perhaps a nick or a hole. Copper can in some circumstances migrate as it does in electroplating, from one terminal to another, although the separator would normally stop that in most cases. If copper breached the separator, the resulting short circuit would cause local heating and might lead to ignition of that cell and then soon after, neighbouring cells would ignite.
If a series connected cell becomes over discharged and is driven by the other cells in its group to a reverse polarity, this kind of copper migration will occur. It is easy to see how a failing cell might fall well below the potential of the neighbours it is in series with, so that would start moving copper from the backing foil to the cathode. Earlier today I read about a battery fire in an old e-bike battery on this very site. I reckon the same cause - worn out cell getting reverse charged by its pals in the series chain.
Most lithium battery chemistries don't need to get that hot to start breaking down and getting into a runaway situation. They need only get to something around 150C to become dangerously over-heated - that's half the temperature of a soldering iron - slightly less. I am thinking that as we begin to depend more on lithium batteries we will see more of the LiFePo4 type, which are not inclined to ignite even in extreme situations.
EDIT: I see that flecc has suggested the same idea more or less. That post was not there when i started this post.
Research into copper deposition where it ought not to be caused by over-discharge and reverse charging:
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Any battery where cells are in series can be subject to the plating effect as copper gets moved when one failing cell in the series is run flat and then gets reverse charged by the others passing current through it. Of course the higher quality involved in cell structure and cell monitoring systems that might detect a cell in a series group going too low and shutting off the flow of current, would solve that.
AI answer to the question, 'How many Nissan Leaf cars have had battery fires?'
"23,887 Nissan Leaf vehicles built between 2018 and 2020 were recalled due to a risk of battery fire:
- Reason for recall
The high-voltage battery in these vehicles can overheat during quick charging. - Owners advised
Owners were urged not to quick charge their vehicles until the issue was resolved.
- In 2015, a Nissan Leaf caught fire and was destroyed on a road in Texas, but no one was injured.
- In 2020, a Nissan Leaf and a house burned down in Ukraine, and a resident died in the fire.
- In 2021, a Nissan Leaf caught fire in Ukraine while charging at a public charging station.
- In 2021, a Nissan Leaf caught fire in Japan after being left outside following heavy rainfall.
- In 2021, a Nissan Leaf caught fire in Russia, possibly while charging with an extension cord.
- In 2021, a 2017 Nissan Leaf caught fire in Ukraine, but the cause is unknown.
In general, electric vehicles (EVs) are less likely to catch fire than combustion-powered vehicles. The U.S. National Transportation Safety Board estimates that there are about 25 fires for every 100,000 EVs sold, compared to about 1,530 fires for every 100,000 gas-powered vehicles sold. "
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If that were true, our ebike batteries would be catching fire left, right and centre. I've had at least 20 batteries in my house for the last 10 years. Not one has done what you suggested, and they're in every state from worn out to brand new.
There is a logical flaw there. Nobody said all batteries develop faults and light up. But some do. The fact that you are coming to your conclusion on the basis of a sample of twenty batteries, does not mean that the man over the road will not have a fire event. If batteries did not sometimes just go up in flames, nobody could have made the following video on the basis of CCTV camera footage.
It wasn't a suggestion, the occasional fire starting from dendrites forming in common cylindrical li-ion cells is firmly established fact. As is the cause, inadequate manufacturing control.
Don't you remember the very large number of laptops exploding in flames when not on charge or in use, thanks to the faulty 18640 cells in their packs? The major cell manufacturing companies had to recall vast numbers of cells.
This was a problem which plagued Tesla for years, delaying the launch of their Model 3 for years due to burnouts during development. Even today with some of their models using over 7000 cells per car they are potentially vulnerable, though they've largely solved the problem currently by manufacturing their own cells, mainly 18640s. However they are still experiencing serious problems with consistency in 21700 and 4680 cells manufacture.
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One point often overlooked is that e-cars still have the 12 volt normal car system powered by the usual lead acid battery for all the usual electrical functions. The traction battery only powers the traction motor through its controller and a low level charger to top up the lead acid battery if that becomes necessary during driving. The 12 volt lead acid battery is normally charged at the same time as the traction battery.
Accordingly EVs still suffer the same 12 volt system fires as I.C. vehicles, in addition to any traction battery fires. Indeed they are the main cause, fires in the simpler traction battery system being far more rare.
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Why would that be true? Yes - you can create a short circuit and set wires on fire with a lead acid battery, but it is hardly common. The battery chemistry is not prone to fire itself, unlike the lithium cobalt and manganese chemistry which when 'out of sorts' can run away and then start making its own oxygen.
I'd agree that Tesla increases their chance of a fire by making batteries with thousands of 18650 cells, because so many cells increases the probability that one of them would go sick and lose capacity and end up getting reverse charged by its companions in whatever series string it is in and therefore start sending metallic copper into the separator and creating a short circuit. However - large celled batteries can also malfunction and turn themselves into a firework. There is a lower probability given the smaller number of them in let's say a Nissan Leaf, but they do catch fire - though less often then the 18650 powered Teslas.
I'm sure the Leaf is a good car, but you may be taking your defence of the brand too far.
I think not, since for almost the first decade of e-cars it was by far the largest seller, yet with the least problems, especially compared to their nearest competitor Tesla and their many fires. Not only that, it was clear that the fires the Leaf suffered were often easily identified as starting in the 12 volt system under the bonnet. I'm sure that with a little thought you might realise why that should be so.
It was clear that Nissan were cautious from the beginning, always putting safety first, being content to launch with only 70 miles range and a top speed below 90mph. Then advancing carefully with small incremental improvements every two or three years.
Compare that to Tesla and another early entrant, BMW, pushing li-ion technology to the limit to claim maximums of supercar acceleration, very high top speed and hundreds of miles range and suffering the consequences. And now of course all newcomers feeling they have to do the same to compete.
Your summary of Leaf fire events shows very clearly that, with the exception of the 2015 Texas fire which as I've previously stated definitely started in the 12 volt system, they only began after the 2018 40kW model that I bought and which has largely remained blameless. That was when they introduced their biggest jump, the modification for a very high performance option using a much larger battery.
This was probably anticipating Tesla's yet to launch Model 3, that being designed to topple the Leaf from its affordability platform. Obviously a Nissan mistake, but followed by Tesla's mistake when their intended Leaf competitor finally turned out to cost at least 56% more than the Leaf at entry level.
My confidence remains as it was in 2018, that my now 7 year old Leaf and it's original battery will serve me to the end of my life or driving days, so confident that I've already paid for my cremation, knowing the Leaf won't do it for me.
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They don't spontaneously explode. They explode because of over-charging, damage, wiring faults, faulty manufacture and things like that. The problem is that the evidence of the cause is usually destroyed during the event, so people have to make weird and unjustified theories about what happened. Through all we know, that Mercedes might have run over an exhaust pipe or hit a speed bump that damaged the underside of the car, or the guy had put his pre-heating on and forgot.
When I was a quality manager, I was dealing with problems and causes all the time. You'd be surprised at the complicated theories that people came up with often backed up by reams of technical data to justify their claims, when the actual cause was always something simple and avoidable.
As I said, if that were true, our ebikes would be bursting into flames and every ebike shop would have burnt down by now.
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