My ebike caught on fire.

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Ebike92119   1 mW

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My ebike caught on fire.

Post by Ebike92119 » Sep 11 2022 10:24pm

Last night I woke up to loud explosions coming from my garage, it sounded like fireworks. I went into my garage and my electric bike was on fire. Sparks were flying and the smell of burning plastic was unbearable. I managed to put the fire out with a garden hose. My neighbor called the fire department. According to the fire department electric bike fires are not uncommon. If I wasn’t home to put the fire out, it certainly woulda caught the rest of my home on fire.

Why did it catch on fire? I’m hesitant to build another bike without figuring out what went wrong. Only one battery caught fire. The other battery is still functioning, which is surprising after it had been soaked with water. I had two unit power pack batteries, one battery was 54v and the other 58v. I had these batteries wired in series making 112v. The battery that caught fire kept turning off, this also happened when the battery was not wired in series. I figured the BMS was turning the battery off. Charging the battery for a few days fixed the issue. While riding around with both batteries in series I noticed the battery that caught fire was getting noticeable hot, but the other battery had a normal temperature. After leaving the bike charging for a few days that’s when the fire started. I’m unsure why the fire started.
Your thoughts and opinions are greatly appreciated.
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E-HP   10 GW

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Re: My ebike caught on fire.

Post by E-HP » Sep 11 2022 11:11pm

Ebike92119 wrote:
Sep 11 2022 10:24pm
After leaving the bike charging for a few days that’s when the fire started. I’m unsure why the fire started.

Your thoughts and opinions are greatly appreciated.
I'm speechless. :shock:

Glad you didn't burn your house down. It might be a sign to switch to a gas powered bike.

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Re: My ebike caught on fire.

Post by LewTwo » Sep 11 2022 11:31pm

Almost any electrical fire is the result of one of two problems:
1) a short circuit (that is why power circuits have fuses/circuit breakers ahead of the loads).
2) a component that gets more current that it can handle and over heats

Certain lithium battery chemistries are safer than others (i.e. LiFePO4 for example) but they have lower power densities and are more expensive. However any lithium battery that actually ignites is "self oxidizing" and you can not put out the fire with water. All water can do is cool the container down.

People that understand the risks do not charge or discharge lithium batteries near their maximum rates. They also monitor the temperature of the batteries during charge and discharge cycles (either manually or electronically). They do not construct unusual power packs that might possibly exceed the capacity of individual components.

Even the experts sometimes screw up. See these news stories:
https://www.bestmag.co.uk/teslas-lithiu ... 300mw-ess/
https://www.energy-storage.news/investi ... australia/
The more I learn the more obvious the immensity of my ignorance becomes.
Weight Wennie E-Bike https://endless-sphere.com/forums/viewt ... 3#p1173723
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ebuilder   10 kW

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Re: My ebike caught on fire.

Post by ebuilder » Sep 12 2022 7:21am

First and foremost, a great relief to learn that just your bike burned and you, family and neighbors are ok.
Second, can you tell us about your ebike? In the wild, it is almost unheard for an 'average' ebike to run at 112v. I personally have never heard of one before. A lot of 84v and 72v bikes running around.

Not to Monday morning quaterback but a lesson for all of us is...when a battery gets very hot during charge or discharge...what LewTwo said, this is not a good scenario.
How were you charging both batteries? Were you charging them at a single point charging point together?...or were you charging your batteries independently?...with two separate chargers?

Can you tell us about what motor you have, what amp controller and your guestimate of net wattage of running both batteries in series?

I think you know not to repeat the same experiment. Glad you dodged this bullet.

PS. can you comment on when you believe the fire started? Was it due to charging?...or just after return from a ride?

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Re: My ebike caught on fire.

Post by From-A-To-B » Sep 12 2022 7:36am

I’m so glad that you are safe and your house didn’t burn down.

Thank you for sharing your story with others, as a warning of ever-present dangers that come with every lithium battery we own and use.

I share my opinion good heartedly, for learning’s sake. It sounds like you noticed and then chose to ignore some warning signs from your battery. The BMS turning the pack off and/or the battery getting hot ought to have prompted further investigation.

Clearly, something was out of bounds and your BMS was trying to prevent an accident. Maybe you had some weak cell groups? Maybe it was giving a high-temp cutoff? Maybe the battery has degraded with time and was now stressed while trying to keep up with your demands? A better response to this would have been to grab the screwdriver and multimeter, rather than throw it on to charge a few days and hope the BMS sorts things out.

In the future, and to anyone else reading this, the first time a battery does something unexpected should prompt a battery health check.

High-quality components and careful use can help mitigate risks, but they’ll never go away entirely. I also wouldn’t personally charge my battery, unattended, while I slept. I do charge in my house, though I try to be around and attentive should something go terribly wrong.

I’m sorry about your battery, and am glad you’re safe.

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Re: My ebike caught on fire.

Post by AHicks » Sep 12 2022 8:47am

This wouldn't have anything to do with that charger laying on the ground under the bike would it? And the burnt off lead going to the battery that didn't catch fire?

I would add to that thought, the insulation between the individual cells, and between the cells and a mounting bracket for instance, can wear out, causing something just like this.

So can inexperienced users messing with big batteries and/or charging combinations that aren't quite kosher.....

You are lucky! I don't blame you one bit for not proceeding until you figure out what went wrong....

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Re: My ebike caught on fire.

Post by 4πr^2 » Sep 12 2022 9:16am

Ebike92119 wrote:
Sep 11 2022 10:24pm
...The battery that caught fire kept turning off, this also happened when the battery was not wired in series. I figured the BMS was turning the battery off. Charging the battery for a few days fixed the issue. While riding around with both batteries in series I noticed the battery that caught fire was getting noticeable hot, but the other battery had a normal temperature. After leaving the bike charging for a few days that’s when the fire started.
Wow. Thanks for sharing. Glad to hear you're OK and not too much damage.

I think some of the 'why' is covered in your quote above. 'Battery kept turning off' is probably the BMS catching a low volt situation and cutting off. Charging 'for a few days' fixed it. Likely this was enough time to 'sort of' balance a bad cell group back up to some sort of reasonable voltage. 'Battery getting hot' another warning sign that something is amiss.

So overall, sounds like you either had a bad cell group(s) or the BMS wasn't effectively charging a cell group(s). This out of balance group got hot and likely lit off during an extended charging period.

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Re: My ebike caught on fire.

Post by thundercamel » Sep 12 2022 1:15pm

Just to make sure you've heard of Louis Rossmann's UPP fire: viewtopic.php?f=14&t=108518

I think pictured here it looks like there is no electrical insulation between cell groups other than the heat shrink wrappers on each cell. If those adjacent cells rub or melt through the wrappers, there will be a short circuit. Maybe a small contact at first was enough to unbalance the cell groups at first (battery shutting off on you) and heat up those cells.

I will say that I only trust ebike batteries with a smart BMS, so that I can manually verify cell group voltages periodically are still balanced. If they aren't, then there's a problem.
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Re: My ebike caught on fire.

Post by amberwolf » Sep 12 2022 2:53pm

I am glad you and yours and your home are safe. I have been thru a house fire (not battery- or EV-related) and lost those I cared about, so I am very glad this didn't happen to you.

There are a few possible causes, but the most likely is the battery itself, internally, since you said it was heating up during charge (which should not happen in a correctly-functioning battery, assuming typical low-current charge rates--it might be warmer than when just sitting there doing nothing, but it should never get "hot".) that also kept turning off. The specific reasons for it to be heating or turning off might be the reason for the fire, or just indirectly have lead to it.

There are other possible contributors: A battery whose BMS is not designed for a voltage higher than the battery charges to may not survive being seriesed with another battery. At the moment when the BMS tries to protect the cells inside against overcharge or overdischarge, the voltage across the FETs (charge and/or discharge) becomes higher than they can handle, and they can fail, often shorted "on", so that the BMS can no longer protect the cells inside against overcharge or overdischarge, even when it is no longer in series with the other battery.

If that happened, then the cells can overcharge, which can cause them to heat up. If they heat enough, they can internally fail and self-discharge very rapidly, which generates enough heat ot cause adjacent cells to fail, which causes a chain reaction that can lead to a fire.

If the discharge port was damaged from overvoltage, and the pack was imbalanced enough, the BMS would not have been able to turn it off (and shut the system down) in the event of cell-group-level LVC, and such a cell group could have been driven negative in voltage and been damaged by that, and failed on a subsequent recharge. (the BMS charge port would *also* have to be unable to shut off for this to happen, because otherwise it would have prevented charge in the first place, if the cell was below it's safety cutoff, unless it is so poorly designed it doesn't have one or can't respond correctly to a voltage at or less than 0V).


The controller doesn't appear to be damaged enough for this (though it may be damaged enough to not work and possibly not be testable for this failure), but another thing that could contribute is that the FETs and capacitors (and LVPS input components) in it also can only handle a certain amount of voltage. If they are not designed for the voltage of the seriesed packs, or the full charger voltage (if still connected to the pack during charge), they can fail, again often shorted (for both caps and FETs), and generate heat, which can lead to a fire if left in that condition, especially if the BMS has already failed from overvoltage so that it can't turn off it's output



Another possible contributor (which may or may not apply to your event) to battery failures is non-balancing BMSs, which many battery sellers use in their cheaper packs, especially in combination with the cheap and non-matched cells they also will typically use in them. The cells grow in imbalance, which the BMS cannot correct as it doesn't have the hardware. The pack capacity will appear to drop, and it won't fully charge, growing worse every usage cycle. It can reach a point where the cells in some groups are nearly empty and others are nearly full, and if the BMS has any form of problem that prevents it from shutting off charge or discharge in the event of cell-level HVC or LVC, cells can be dramatically overcharged or overdischarged (even to the point of going negative in voltage, which is even worse for them than other conditions), and that can lead to a fire.



Cells can also just fail internally, from manufacturing defects. This shouldn't happen (at least, very very rarely) from properly QC'd cells being used well within their specifications, but many cheap packs are probably made from cells that didn't pass QC in some way, and many (perhaps most) packs regardless of price are setup to use their cells right to the edge of their capabilities (which means that even with perfect cells to start with, as they age they'll become incapable of handling the usage they're put to, and be stressed more and more, with greater risk of failure).

We know from troubleshooting disassembly inspections in various threads that some cheap packs are made from recycled garbage cells from discarded packs from assorted sources. Some places may sort those and use only verified good ones, but QC takes time and money, so cheap packs probably don't do that, and we've seen packs that show signs that cells get used regardless of condition (even when obviously physically damaged before or during assembly).




Ebike92119 wrote:
Sep 11 2022 10:24pm
Last night I woke up to loud explosions coming from my garage, it sounded like fireworks. I went into my garage and my electric bike was on fire. Sparks were flying and the smell of burning plastic was unbearable. I managed to put the fire out with a garden hose. My neighbor called the fire department. According to the fire department electric bike fires are not uncommon. If I wasn’t home to put the fire out, it certainly woulda caught the rest of my home on fire.

Why did it catch on fire? I’m hesitant to build another bike without figuring out what went wrong. Only one battery caught fire. The other battery is still functioning, which is surprising after it had been soaked with water. I had two unit power pack batteries, one battery was 54v and the other 58v. I had these batteries wired in series making 112v. The battery that caught fire kept turning off, this also happened when the battery was not wired in series. I figured the BMS was turning the battery off. Charging the battery for a few days fixed the issue. While riding around with both batteries in series I noticed the battery that caught fire was getting noticeable hot, but the other battery had a normal temperature. After leaving the bike charging for a few days that’s when the fire started. I’m unsure why the fire started.
Your thoughts and opinions are greatly appreciated.
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PaPaSteve   10 W

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Re: My ebike caught on fire.

Post by PaPaSteve » Sep 12 2022 3:24pm

Scary stuff :shock:
Thank goodness it was caught in time.
Is it possible two different battery pack voltages might be a contributor ?
One pack is 54V the other 58V ?

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Re: My ebike caught on fire.

Post by 999zip999 » Sep 12 2022 3:31pm

Without a diode between the two packs the 58 volt pack would rush in to the 54 volt pack as fast as it could
So UPP battery ?
What controller ?
What amps were you running ?
What motor ?

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Re: My ebike caught on fire.

Post by hemo » Sep 12 2022 4:38pm

The OP needs to give more detail as others have referred to.
Were the batteries being charged ?
If so how ? In parllel , in series or individually ?

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Re: My ebike caught on fire.

Post by slaphappygamer » Sep 12 2022 5:04pm

I’m glad you are ok and that you still have shelter.

My 2 big takeaways from your story are, don’t use differing voltages in series and not to leave your bike charging for a few days.

Hopefully, other fires will be prevented from you sharing your story.

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Re: My ebike caught on fire.

Post by JackFlorey » Sep 12 2022 6:32pm

Ebike92119 wrote:
Sep 11 2022 10:24pm
I had two unit power pack batteries, one battery was 54v and the other 58v. I had these batteries wired in series making 112v. The battery that caught fire kept turning off, this also happened when the battery was not wired in series. I figured the BMS was turning the battery off. Charging the battery for a few days fixed the issue.
Here is a very common scenario:

1) The battery gets out of balance for one of a dozen reasons (poor cell matching, construction, poor BMS design etc)
2) One cell gets significantly higher than the rest.
3) During a charge, the cell regularly gets charged to 4.5 volts or so and the BMS does not notice.
4) Dendrites form inside that cell.
5) One day a dendrite gets long enough to bridge both electrodes. That causes a short and it heats up that area of the cell. The electrolyte decomposes and begins providing oxygen. Oxidation of the lithium metal, and then the electrodes, starts.

After that the thermal runaway has begun and cannot be stopped.

The fact that it kept cutting out suggests that that is the problem. The BMS limits may have been set "generously" (i.e. 4.5 volts) or they may simply not be very accurate. So it charges to 4.5 and cuts out, 4.5 and cuts out, finally the balancer works and now you are only charging it to 4.4 volts - which is still enough to, over time, plate out lithium and cause dendrite formation.

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Re: My ebike caught on fire.

Post by amberwolf » Sep 12 2022 7:42pm

slaphappygamer wrote:
Sep 12 2022 5:04pm

My 2 big takeaways from your story are, don’t use differing voltages in series
<snip>
Different voltages in series don't cause a problem (not this kind, anyway).

Different voltages in *parallel* can, assuming no diode-like device to prevent the lower from dragging down the higher (with various possible problems depending on circumstances).
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Re: My ebike caught on fire.

Post by slaphappygamer » Sep 12 2022 7:55pm

Thanks for schooling me, @amberwolf. I would like your post, if I could. :)

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Re: My ebike caught on fire.

Post by docw009 » Sep 12 2022 8:53pm

When you have two packs in series, the voltage is not the issue. It's whether the BMS on either pack can hold off the combined voltages of both batteries, if it shuts off. YOu have 112V at peak charge, and I doubt the transistors in a a 13S BMS can hold off more than 100V.

If you put packs in series, you have to look at your BMS, get the MOSFET part numbers and look them up. The MOSFET's on this Annpower 13BMS are Infineon BSC030N08N only rated for 80V . For sure, they would eventually blow at 112V. and maybe fail short circuited. I believe Amberwolf describes this scenario. Now I would have no protection during charging or discharge.
P9121101.JPG
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I think you had a low voltage cell group in the burned battery that should have been isolated, but a short circuited BMS allowed them to get recharged and they became heaters.

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Re: My ebike caught on fire.

Post by PaPaSteve » Sep 13 2022 9:37am

docw009 wrote:
Sep 12 2022 8:53pm
When you have two packs in series, the voltage is not the issue. It's whether the BMS on either pack can hold off the combined voltages of both batteries, if it shuts off. YOu have 112V at peak charge, and I doubt the transistors in a a 13S BMS can hold off more than 100V.

If you put packs in series, you have to look at your BMS, get the MOSFET part numbers and look them up. The MOSFET's on this Annpower 13BMS are Infineon BSC030N08N only rated for 80V . For sure, they would eventually blow at 112V. and maybe fail short circuited. I believe Amberwolf describes this scenario. Now I would have no protection during charging or discharge.

I think you had a low voltage cell group in the burned battery that should have been isolated, but a short circuited BMS allowed them to get recharged and they became heaters.
So ... regarding the BMS and trying to understand your your theory.
Were the two battery packs set up with in such a way to use only one BMS which then sees full pack voltage ?
Or was there two BMS's one for each battery pack which then sees individual pack voltage ?

Either way ... an individual cell shorting out causing a runaway fire episode makes sense.
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Re: My ebike caught on fire.

Post by thundercamel » Sep 13 2022 9:50am

PaPaSteve wrote:
Sep 13 2022 9:37am
Or was there two BMS's one for each battery pack which then sees individual pack voltage ?
I was just going to say, the high voltage is a rare variable to think about, but each pack should have had it's own BMS and neither should have seen the full series voltage. Hopefully both chargers had floating/isolated DC output voltage...
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Re: My ebike caught on fire.

Post by ebuilder » Sep 13 2022 11:01am

thundercamel wrote:
Sep 13 2022 9:50am
PaPaSteve wrote:
Sep 13 2022 9:37am
Or was there two BMS's one for each battery pack which then sees individual pack voltage ?
I was just going to say, the high voltage is a rare variable to think about, but each pack should have had it's own BMS and neither should have seen the full series voltage. Hopefully both chargers had floating/isolated DC output voltage...
Still unknowable. Haven't heard back from the OP. I asked early in the thread what his charging strategy is. If he was commonly charging both batteries with a single charger...say through the discharge port, all bets are off.
I have 'never heard of' two shark batteries placed in series to create 112v on a non-Emotorcycle type average ebike pictured. We have no idea about the controller or motor, charging protocol or anything because he hasn't responded.
I know personally, I would never connect two batteries in this manner. Connecting batteries in parallel is of course a more common strategy to increase amp-hrs and range. But this does not affect net power through the motor and controller like elevating voltage by a factor of 2 x's.
I have heard of small series additions to say an existing 52v battery to increase voltage to 72v. 2 x 36 volt batteries in series is sometimes done. Many controllers and motors can handle 72v. But never heard of 112v with two good sized batteries. I know a Tesla automobile will handle a fair amount more. ;-)

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Re: My ebike caught on fire.

Post by tomjasz » Sep 13 2022 11:49am

thundercamel wrote:
Sep 12 2022 1:15pm
Just to make sure you've heard of Louis Rossmann's UPP fire: viewtopic.php?f=14&t=108518

I think pictured here it looks like there is no electrical insulation between cell groups other than the heat shrink wrappers on each cell. If those adjacent cells rub or melt through the wrappers, there will be a short circuit. Maybe a small contact at first was enough to unbalance the cell groups at first (battery shutting off on you) and heat up those cells.

I will say that I only trust ebike batteries with a smart BMS, so that I can manually verify cell group voltages periodically are still balanced. If they aren't, then there's a problem.
Two 72V batteries on a BBSHD with an "upgraded" controller. Not a good example...
That said, the reseller I worked for sold UPP batteries and had high failure rates and the shop insurance paid out $50,000 for a UPP battery fire.
Thanks Justin_le we're here thanks to you. All the best to the mods for their tireless work keeping it on an even keel.

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