Ebike batteries

Hi folks, havn't posted for a while but I have been wondering off and on about battery safety if you unfortunately have a accident with a vehicle. I know battery safety is the last thing you will be thinking of if you survive impact but if a car does collide with you side on and hits battery what are the chances of battery exploding at impact, at say 20-30mph.

I've not looked for examples, so I might be completely off-base here, but I feel like the risk of explosion in a crash is pretty small.

 

Most ebike batteries are a collection of cylindrical cells like 18650s or 21700s, and to puncture those takes a lot of force. I'd imagine the bigger risk would be for a fire after the crash, as something in the battery could get shorted as tumbles around and things break inside, leading to thermal runaway. I'm not aware of either happening though.

 

Someone more knowledgeable than me is more than welcome to say I'm wrong!

Lithium batteries are used in gazillions of portable devices.

 

Is there much history of these devices directly exploding when dropped or knocked ?

 

For sure if a lithium batttery is damadged in a collision the thermal runaway process might start which some time later causes a fire, but thats not exploding on impact.

It is highly unlikely for a battery to explode. Battery might catch fire immediately after impact, hours, days or weeks later.

I would think that if your bike, and therefore you, suffer an impact strong enough to damage the battery and it's casing, then battery fire is going to be the least of your worries.

I would think that if your bike, and therefore you, suffer an impact strong enough to damage the battery and it's casing, then battery fire is going to be the least of your worries.

As already pointed out I did say it would be least of my problems, just wondering from a technical point of view

18650 or cylindrical celsl are generally safe , they only have issues with poor charging regimes, using an incorrect charger or trying to by pass the BMS when an error initially prevents charging.

 

I have had a 3s 18650 booster soft pack get damaged by hittting the ground , on a ride I forgot to zip up the rear top rack bag/pannier and the cell pack jumped out after hitting a bump the damage was limited to one cell with took the brunt and the cell can was pierced. It leaked the cellulite but no major short occurred otherwise, my spot welding held firm so no shorting occured. I was able to replace the damaged cell and still use the 3s pack today.

If it gets detached and goes bouncing down the road, a well constructed battery with well supported cells and properly spot welded interconnections will probably be fine in an impact at those speeds. But you wouldn't want to be hit by it.

 

Trapped between a vehicle and something solid and immovable? It will be crushed and then highly likely to burn.

Hi folks, havn't posted for a while but I have been wondering off and on about battery safety if you unfortunately have a accident with a vehicle. I know battery safety is the last thing you will be thinking of if you survive impact but if a car does collide with you side on and hits battery what are the chances of battery exploding at impact, at say 20-30mph.

The answer is very simple. It's close to zero. If you like worrying about stuff, you'd be better spending your time worrying about things that there's a much higher chance of actually happening, like getting struck by lightning or falling out with your partner and going suicidal.

The answer is very simple. It's close to zero. If you like worrying about stuff, you'd be better spending your time worrying about things that there's a much higher chance of actually happening, like getting struck by lightning or falling out with your partner and going suicidal.

I'm not particularly worried about it, just curious

Cells would need to be punctured or crushed (i.e. split open). So perfectly landing on something very pointy with a huge amount of force to not deflect off, or landing in a hydraulic press. Bouncing down the road and being run over by a truck wouldn't be enough force I don't think but I sure would watch that YouTube video if someone wants to try it. Who knows.

Batteries do not explode. When they catch fire, enormous amount of toxic smoke is produced and fire is very hard to put down, but it is not an explosion like a hand grenade if this is what you are asking for.

Batteries do not explode. When they catch fire, enormous amount of toxic smoke is produced and fire is very hard to put down, but it is not an explosion like a hand grenade if this is what you are asking for.

Ok thanks Az, at least I can rest easy knowing my legs won't get blown off, or anything else!

Two vans travelling sideways at near light speed hitting the ebike battery from opposite directions could start self-sustaining fusion which ignites the earth's atmosphere. It's a road scenario I do my best to avoid, despite how vital cracking fusion is for humanity.

This one was delivered to me after travelling half way round the world in the loving care of DHL:

 

http://www.flecc.uk/t/images/ezeecracked.jpg

 

As you see the case shattered by an impact. After I repaired it as below with silver duct tape, it worked perfectly for the rest of its life:

 

http://www.flecc.uk/t/images/silverrepair.jpg

Two vans travelling sideways at near light speed hitting the ebike battery from opposite directions could start self-sustaining fusion which ignites the earth's atmosphere. It's a road scenario I do my best to avoid, despite how vital cracking fusion is for humanity.

I too am concerned by dictatorships seeking global domination. My ebike battery could initiate thermal runaway were my house to receive a direct hit from an ICBM.

I did a deep dive into this subject before buying my bike and my considered opinion is pretty much all of the fires are down to people using them in ways they weren't meant to be used or buying components that weren't built properly.

 

It strikes me that the vast majority of ebike fires are down to incorrect charging. Don't leave an ebike battery unattended when you charge it, and don't use the wrong charger.

I have shot 18650's with my air rifle they don't catch fire.

I have shot 18650's with my air rifle they don't catch fire.

 

Were those cells particularly hated? Which type where they?

Hi folks, havn't posted for a while but I have been wondering off and on about battery safety if you unfortunately have a accident with a vehicle. I know battery safety is the last thing you will be thinking of if you survive impact but if a car does collide with you side on and hits battery what are the chances of battery exploding at impact, at say 20-30mph.

 

Unless the battery is smashed with extreme force into tiny partcles, and end up being suspended in air, surface area greatly increased and they ignite at pretty much the same time, I really don't think an explosion is possible.

 

 

 

Don't surround your battery pack with flour.

 

https://en.wikipedia.org/wiki/Tradeston_Flour_Mills_explosion

Edited February 13, 20242 yr by guerney

They were older worn out Sam 22e or 26f cells. The lipos I shot were a bit different and did spark and crackle a bit but didn't catch fire they did whiff a bit as they let out the electrolite. It was all carried out in the name of a science experiment .

They were older worn out Sam 22e or 26f cells. The lipos I shot were a bit different and did spark and crackle a bit but didn't catch fire they did whiff a bit as they let out the electrolite. It was all carried out in the name of a science experiment .

 

I knew you'd keep detailed files.

"Although two people managed to escape, two men weren’t able to as the fire blocked their exit - meaning they had to hang out the window and be rescued by firefighters."

https://www.standard.co.uk/news/london/ebike-fire-whitechapel-man-rescued-london-brigade-b1138839.html

https://theconversation.com/self-extinguishing-batteries-could-reduce-the-risk-of-deadly-and-costly-battery-fires-222667