Lipo fire- no one hurt- my fault

[BikeFanatic]

I am posting to document my lipo fire for all you all In the spirit of deconstructing the incident so further episodes can be avoided.

Yes I realize I made a stupid mistake that I was complacent, and that I could have hurt myself or someone else and believe me. I understand that. I did not have to report this. I wasnt going to this happend just before christmas, but changed my mind.

so any non mean spirited comment or criticism is welcome, I think I know already what caused this lipo fire. I thought it was the rain but now i see I hooked two fully charges batteries of different voltages together in parallel.


I am no battery expert, I have been playing with Ebikes for many years, since 2004, and I have learned to fix my ebike, rebuilt a few batteries that have a bad cell for example. I am a hack, a former newb who knew nothing,but has learned alot reading here and fixing up my ebike.

I use Lipo for my Ebike as well as using a single 3 and /or 4 series 5 AMPHR to power my headlights.
I use vinyl/plastic tube bags to hold the batteries. One side is mesh the other plastic and you can use a shower cap to cover it further and protect it From rain.well I ride in the rain snow and sleet all winter for years and never had an issue with a shorted battery. But i do usually take extra precautions when I know rain is coming.

so I was riding to work very early in the morning, on my ebike, it started pouring rain monsoon like, then slowed down, 20 minutes later i am almost at work and I hear PSSSSST, like a short and something evaporated, say a balance wire. I continue on another minute or two I am now riding slow on the sidewalk over took a pedestrian just pedaling slowly, ten seconds later my 3 series 5 AMPHR lipo burst into flames. It was seated in front of me near the handle bar area in a bag. next thing I remember I found myself on the ground patting my self ( but I wasn't burnt), then on my feet to try to separate any of my other lipos from contributing to the fire. I was soaked and did not have any burns, it flamed for about a minute once the flames piddled down I pat it out with my glove. I was very lucky no one was hurt, only one witness and she was like “Oh my god” but did not panic or call 911, just came to help me up. The fire was dramatic, flames shooting out with gassing and venting, but over quickly and i reeked like smoke when i got to work.


I could not find the pack that night but finally Days later I went back in daylight to find the remains that I kicked into the wooded area.That’s when I noticed that I had hooked a fully charged 3 series pack to the fully charged 4 series in parallel .
I use power poles for everything. I make all my connections the night before, but apparently in my early morning haze I forgot and thought I was hooking my light to a battery.

SO you can see I found the wires came off, melted off I guess , no sign of shorting there
I measured the voltages of the four series battery and all cells are at 3.10 volts.

I am concluding that it was an overcharged 3 series that caused the fire.
I suppose there could have been a short also but all the evidence is burnt up except the very intact power leads.
Here are some pics below

 

[BikeFanatic]

here are the remains

 

[BikeFanatic]

reserved for pics

 

[FastDemise]

Edited by request of OP.

 

[TMaster]

Sorry for the loss. Good thing you are ok, and hopefully it wont be too costly for the repairs.

How Could the 3S pack have been over charged? Wouldn't it baloon and ignite durring the over charging process? Maybe it was puffed already from overuse, or over charging and you didnt see it before you started out for the day?

This is another story to add to the list why I would never run lithium polymer batteries on a ebike. Sure i have contemplated many times about running lipo's because of the less costs and density compared to lifepo4's, but it's not worth it. All it takes is 1 small mistake in care and feeding of lipo's to have something go bad. And for those guys out there that say: " oh lifepo4 cells can ignite just like lipo's" etc etc... I ask that you go compile a list on lipo puffing/fire etc, compared to lifepo4's and bet it will be 10 to 1 or even 100 to 1. And that 1 would most likely be to an extreme case where negligence was involved.

My two cents for lipo's:
Always, physically check lipos by eye and hand before you start the ride.
Always check individual cells voltages before and after charging.
Always replace puffed cells or packs. ("Oh it's not puffed that bad" = accident waiting to happen)
And if you really want to be anal, don't ever peak charge lipos, or take them to the LVC. Capacity loss from 1 cell could take that cell down past the LVC = puff = fire.

 

[TMaster]

Was that whole bag soaked with rain water?

 

[Ricky_nz]

This is another story to add to the list why I would never run lithium polymer batteries on a ebike.

Why pollute a thread looking into a failure with personal RANTS about battery types?
Its better to discuss why and how to avoid the issue rather than hiding that information under a pile of I wont use blah blah blah.
This failure/mistake could have been made with other battery types with similar results.

The real problem is that the pack is being regularly broken down at the connectors which makes it easy to reconnect in the wrong way. Its best to permanently connect as much as possible of the pack so there is less points of failure due to human error

 

[bigmoose]

Would you be willing to post a summary of your thread with a pix or two on this 2013-Li Battery Catastrophic Event Summary Thread?
http://endless-sphere.com/forums/viewtopic.php?f=14&t=46851

I think you already have a good lessons learned in your connector issue.

 

[BikeFanatic]

I forgot to say the 3 series pack was brand new and tested with a cellog 8 - it gave 4.5 amphours, and the water, well I
Just do not know if the water contributed. the side pocket was wet and the batteries were wet, but not full of water.

 

[SamTexas]

Sorry about your loss. Glad you're not hurt.

This failure/mistake could have been made with other battery types with similar results.

If this same mistake was made with laptop LiCo, it would have been a non-event. The cells in the smaller pack will be just a little overcharged. I have simulated much more severe scenarios and still could not get the cell to burn or explode.

 

[BikeFanatic]

Thank you for your well wishes.
For now I am assuming the 4 series overcharged the 3 series, so the 3 series cells would be about 4.90 volts each
or more, is that the point where they outgas? the 4 series I hooked it to was fully charged as well, then when I examined the 4s later all the cells were down to 3 volts.

 

[TMaster]

This is another story to add to the list why I would never run lithium polymer batteries on a ebike.
Why pollute a thread looking into a failure with personal RANTS about battery types?.

It was a little ranting on the lipo's in comparison, but if someone see's that and it saves failure in the future, then it's worth it.

Its better to discuss why and how to avoid the issue rather than hiding that information under a pile of I wont use blah blah blah.

I did discuss why and how to avoid issues. I made a list of things.

This failure/mistake could have been made with other battery types with similar results.

Not bloody likely! Just kidding, but lithium polymer is the most volatile battery chemistry that I know of and most other types would have just smoked or went to 0V.

The real problem is that the pack is being regularly broken down at the connectors which makes it easy to reconnect in the wrong way. Its best to permanently connect as much as possible of the pack so there is less points of failure due to human error

No, if that was the case, he would have shorted the connectors right away and failure would have been in seconds.

 

[TMaster]

Thank you for your well wishes.
For now I am assuming the 4 series overcharged the 3 series, so the 3 series cells would be about 4.90 volts each
or more, is that the point where they outgas? the 4 series I hooked it to was fully charged as well, then when I examined the 4s later all the cells were down to 3 volts.

How could a 4 series battery over charge a 3 series battery? It can't. The voltages are not going to blend accross the cells from pack to pack when you hook them up.

Is the 3 series pack the same Ah as the 4 series pack?

 

[TMaster]

Bigmoose, Here is a link to a collected over 200 seperate lipo related failures/fires. The RC world has been using lipo's for 8 years or so. Not sure if you want to use this information or not.

http://www.rcgroups.com/forums/showpost.php?p=15776103&postcount=4

 

[amberwolf]

How could a 4 series battery over charge a 3 series battery? It can't. The voltages are not going to blend accross the cells from pack to pack when you hook them up.

Yes, it can, and yes, they are. (EDIT: assuming you hook the main leads together, as the pictures here appear to show. If only hooking balance leads together, then no, it wouldn't.)

If you hook up the main leads of a higher voltage pack to a lower voltage pack, with no current limiting besides the internal resistance of the cells and the wires, then current will flow at the maximum rate possible from the higher V pack to the lower V pack.

As this happens, V and state of charge will rise on the lower voltage pack as the V and SOC on the higher voltage pack lowers.

If there is enough capacity in the higher V pack, it could severely overcharge the lower V pack, up to the point at which voltage is equal between the two packs (at which point current flow stops, and up to which point current has been dropping since the initial connection).

If the resistance of the wires or connections is higher than that of the cells, more power will be dissipated across that resistance, whcih though small will still create some heat at the currents most of the RC LiPo is capable of. If the reistance of the cells is higher, then more power will be dissipated within the cells themselves, heating them internally more than the wires are heated. Both things will heat up some regardless, it just depends on which has higher resistance as to whcih will dissipate more power as heat. Whether that heat has anything to do with the fire would depend on the resistance and thus the actual current flow and power dissipated, as well as the original voltage difference, and what exactly happens inside the cell as it warms up.



Anyway, stuff definitley does happen if you connect two different voltage sources (PSU, capacitor, or battery), and they will try to equalize voltage potentials thru the resistance of the resulting circuit, and current will flow, and heat will be generated.


EDIT: added:

SHow Could the 3S pack have been over charged? Wouldn't it baloon and ignite durring the over charging process?

Assuming that what happened was actually a 4S plugged into a 3S, then that sounds like exactly what happened--while riding it was being overcharged, and took just that ~20-25 minute time to overcharge and react to it.

I would be curious to see what the actual current flow would be from a 4S to a 3S of this type of pack. One could plug a wattmeter in between them to see, but I think it would risk melting the shunt off the board of a Turnigy Watt Meter or Watts Up; a larger external shunt meant for high-current and hooked to a Cycle Analyst or voltmeter (knowing the shunt resistance, and thus being able to calculate the current from the resulting voltage across the shunt) would probably be safer. A clamp-on ammeter would also probably work but a wattmeter to log everything would be best.

I have some defective packs with cells that won't hold a charge I could use to test something like this, but I doubt the results would be the same as with good working packs, and I don't have enough of the bad cells to make a 3s and a 4s; I'd have to try it as a 2s and a 1s, whcih would be a much more severe overvoltage and thus overcharge.

The real problem is that the pack is being regularly broken down at the connectors which makes it easy to reconnect in the wrong way. Its best to permanently connect as much as possible of the pack so there is less points of failure due to human error

This is true. Adding a "charge port" to a system that is otherwise always left connected would reduce human error to potentially misconnecting the charger or connecting the wrong charger (presuming it is not keyed).

Adding a high-current fuse (rated above the peak current you'd see in normal use) on each pack would also help in some cases (don't know about this one, but reverse-connection would pop them.

 

[liveforphysics]

Plugging a charged 3s pack to a charged 4s pack does result in fire. This has been well tested (most often by accident).

That was a very nice looking ebike before the fire. Do you have a link for that little bag? Ive got a roadbike im building that could use a little bag like that.

 

[neptronix]

If you had 10 amp hours or more, the power from the pack woulda been so powerful that it would have blown the power leads of one pack right off and prevented the fire.

Any other battery would have reacted adversely to some degree. Instead of dead cells, you got dead firey cells.
Glad to hear that nobody got hurt.

 

[wesnewell]

How could a 4 series battery over charge a 3 series battery? It can't. The voltages are not going to blend accross the cells from pack to pack when you hook them up.
Is the 3 series pack the same Ah as the 4 series pack?

4s pack is 16.8V charged. 3s pack 12.6v charged. When you parallel them at the mains as he did, they try to equalize.This means the 3s pack has to charge to 14.7V or 4.9V per cell. Over charge a lipo cell to 4.9V and the result will sometimes be a fireball. Try putting 4.5V per cell in your lifepo4 pack and see what happens. Or try charging you car battery with 18V @100A and see what happens. Do not stand close to either if you value your life.

 

[mikebikerad]

Hobbyking hardcase packs won that voltage tug of war.

 

[fizzit]

I'm very glad that I got a 44v charger instead of re-configuring my pack every night. I had to switch series/parallel stuff in order to charge for a little while and I plugged two hardcase packs into each other. Luckily no fire, just one of the cell tabs became smoke.

 

[TMaster]

Sorry guys I was under the asumption that the 3S and 4S packs were hooked in series to make a higher voltage to run the bike. He didnt explain his total battery setup. I don't know anyone that runs such a low voltage lol. The bike is run on 14.8V total??? Of course the voltages would act like that in a parrallel formation. But I dont think they would in series as I was explaining eariler would they?

 

[oatnet]

Glad you were not hurt, although it breaks my heart to see it happen to an S-750 frame. In case others have not mentioned it, the aluminum in that frame was probably weakened by the fire. It may need to be properly annealed before it is safe to use again - it would be unpleasant to have a weakened headtube shatter under load.

-JD

 

[dogman dan]

I agree, that frame is no longer safe to ride. Bummer.

Cause of the fire is obvious, 3s paralelled with 4s. Interesting though, that it didn't fire up instantly, or pull enough amps to melt tabs and stop it.

Makes you want to think about a thermometer inside the battery compartments. Mabye a light that flashes or a beeper if the battery gets hotter than 120F or something?

Any time you assemble lipo bricks into a pack, slow down, think about what you are doing. If you do it regularly to charge, as I do, set up a routine for doing it right, and do it the exact same way every time. I KFF'ed a few times in the first 3 months I had lipo, and haven't done it since.

 

[etriker]

Ouch !

Lipo killed that electric bike.

And lipo for lights ? How much C do lights need ?

This lipo life style with the burning batteries and the kff and all ? ? ?

I got ran off the road by a garbage truck Friday. Just riding an electric bike is crazy enough for me.

Don't need no lipo fires making it more crazy !

 

[dogman dan]

Not trying to bash lipo, I love it and use it.

But I like lifepo4 better for routine transportation riding that requires only 2c for my needs. I use lipo mostly on high performance ebikes for weekend fun.

In a way, the extra hazard is just part of the fun, much like playing with guns, flamethowers, etc. Just like other potentially dangerous toys, a bit of common sense and basic precautionary rules ensures safety. Like when you pick up a gun, try to unload it before you do anything, then when certian it's unloaded, including a round in the chamber, you still never do anything as stupid as pointing it at somebody.

The most dangerous thing in your house is likely the shower stall, but you don't give up washing you ass.