e-bike Battery Fire

[jonovid]

e-bike unitpackpower Battery Fire.

Louis bought a unitpackpower battery. used it to less than 40% its continuous rated power output. and It exploded. 

[SilverSolder]

There is something reassuringly safe about a 1200cc turbo ICE motorcycle! 

[Fred27]

Motorcycles and turbos have never been a good combination.

[maginnovision]

For cruisers it hardly matters. You take a big heavy bike(say the nice new BMW R18) and throw a turbo with a few pounds of boost on it and you'll still be slower than a higher performance bike(600cc sport bike could give you a run on a straight and run circles around you on a track). Unless you go extreme boost then maybe you'll get a bit more but size and weight still hold you back. Drag racing bikes are a good combination for turbos because you really want to keep that package compact and it costs a lot to get power most other ways since so much ends up being custom.

For your typical sport bike/standard bike it's sort of silly though*. You can already buy bikes that'll easily go fast enough to get you in trouble very quickly and on a track you'll end up needing more brakes than you can get. That's not to say it wouldn't be fun but you need to plan a bit more.


*Ducati streetfighter V4 - 208hp, 90 lb-ft
*Ducati Panigale V4 - (S) 214hp, 91.5 lb-ft, (R)234HP, 83lb-ft
*BMW S1000XR - 164hp, 84lb-ft
*BMW S1000RR - 205hp, 83lb-ft
*KTM 1290 Super Duke R - 180hp, 103lb-ft
*Yamaha MT-10 - 158hp, 82lb-ft
*Yamaha R1 - 197hp, 83lb-ft

[Marco]

Was it really the battery which initiated the failure? How well was everything protected against a FET failing short in the BMS or motor controller?

[Ian.M]

Was it really the battery which initiated the failure? How well was everything protected against a FET failing short in the BMS or motor controller?

Did you skip the video after the exciting bit? The BMS was integral to the pack, fitted and supplied by the battery manufacturer (so if it failed its their liability, same as the battery), and Louis salvaged the motor and its integrated controller and demonstrated they were still fully functional, so there couldn't have been a MOSFET failure in it.

[tszaboo]

Here is a regular 50cc moped which was on fire, next door where I was living. There was markings due to smoke on the 2nd floor balkony.
Nothing new. These things are noisy, cheap, badly built, environmentally unfriendly, unreliable and unsafe things, that sell for X99. Just walking near them, you can feel the cancer in your lungs. It's like you can just bite the hidrocarbons from the air.

The electric ones are just badly built, unreliable and unsafe things, that sell for 1X99.
Out of context. Stupid, didnt watch video.

[tszaboo]

So the manufacturer is actually somewhat right. You cannot place just two random lithium batteries in series or in parallel. A battery pack is built from cells, not from batteries.
batteries =/= cells
He looked at the cell datasheet, and concluded, that the battery pack built from these cells, should have the same current capacity, as the cells.
Also, that bridge rectifier. So at 54A, it would dissipate around 50W. Like a modern CPU with a large heatsink and fan. Was there a heatsink and a fan on those diodes?

[jonovid]

This battery fire video reminds me of modified performance cars & bikes at the speedway, you keep tweaking, adding power until something blows.
the 1st e-bike he had was ok, then Louis bought a yellow cargo bike & stated adding batteries, pushing the limits more. 
60 to 80 amps at 84 volts wo  9,600 Watts on an e-bike. that is motorcycle power levels.   

what I have learned about them
e-bike motors start at gutless 250 watts and go all the way up to 2500 watts for direct drive hub motors.   3k watt motor is a motorcycle!
so why bother with bicycle pedals and a lack of suspension?   
you can over volt an BLDC e-bike motor, so a motor that is designed for 48volts can be made to run at a hot 52volts with a boost in power.
most e-bike batteries from types 24V , 36V, 48V and 52V. at 8 , 10 , 12 or 20 amps,  wiring harness is the limit on amps.
paralleling batteries for more range is something I would never do,  swapping out batteries yes.   
fuse and circuit breakers are a must here. go figure.   

[bdunham7]

Motorcycles and turbos have never been a good combination.

Check out how fast it goes from 140mph to 190mph.

[maginnovision]

Not quite the same as a turbo 'busa you also have the kawasaki ninja h2 which is a factory supercharged bike with ~310hp and 115lb-ft torque.

[Siwastaja]

Who came with this stupid bridge rectifier idea? Any thermal design being done? It's not rocket science! Doesn't this guy know that diode current rating is meaningless? I * Vf * (Rth_j-c + Rth_c-hs + Rth_hs-amb) matters. Claim that putting 50A through 100A rated diode bridge is "conservative" shows this guy has no freaking idea about the most basic electronic design work. That stupid bridge dissipates some 100W at 50A. Where is it located? How about heatsinking? Being like three-four soldering irons set at full power, it's well capable of externally inducing thermal runaway on the pack if located close. Worst of all, he's getting correct advice from the battery pack manufacturer, saying putting these battery products in parallel, series, or using such bridge rectifier circuit, is dangerous and shouldn't be done. But he doesn't listen because he has mixed up cells and batteries himself. Dunning-Kruger is really showing in this video, and the fan echo chamber really doesn't help.

In addition to crappy circuit design and construction techniques, I'm suspecting the authenticity of the cells. Buying a random, no-name, poorly constructed Chinese pack with "Samsung 35E" cells, why would you expect to receive anything but counterfeits?

Proper cells have quite some passive safety. You can set them fire if you totally fail the design (especially by heating them up beyond some 150 degC with external heat source, such as failed electronics), but it will happen way easier with crappy cells lacking passive cell-level safety.

Who knows what happened. My impression on many battery pack fire videos is that they are horrible hacks where I can instantly see so many things being wrong it's impossible to say what is the root cause. On the 'net speculation, it is always because of having a BMS, or because of not having a BMS (in either cult, what the BMS actually is and how it's designed seems irrelevant.)

Issues with Rossmann's joke circuitry are undeniable; but it's highly likely such pack has manufacturing problems as well. As usual, accidents tend to happen when multiple things go wrong at the same time.

It's scary how crappy li-ion cells and packs are sold to completely clueless hobbyists; they are finicky technology which requires some real understanding at every level of design. But if you think about it, someone with a bit more understanding would do their due diligence while buying such products, including inspecting what they get.

[bdunham7]

Claim that putting 50A through 100A rated diode bridge is "conservative" shows this guy has no freaking idea about the most basic electronic design work. That stupid bridge dissipates some 100W at 50A. Where is it located? How about heatsinking?

I don't know how he handled the heatsinking, but in that configuration if Vf = 0.6V per diode, it looks to me that it will only dissipate 30W at 50A system current.  The current from each battery goes through one diode.  And he only had 46A peak, the average was something quite a bit less. 

[Siwastaja]

I don't know how he handled the heatsinking, but in that configuration if Vf = 0.6V per diode, it looks to me that it will only dissipate 30W at 50A system current.  The current from each battery goes through one diode.  And he only had 46A peak, the average was something quite a bit less.

At 1000V rating, it's not going to be a schottky, but a normal Si diode. At 50A, Vf will be definitely at least 1.0V if not more. Definitely not 0.6V.

[bdunham7]

At 1000V rating, it's not going to be a schottky, but a normal Si diode. At 50A, Vf will be definitely at least 1.0V if not more. Definitely not 0.6V.

I missed the 1000V rating, that does seem silly.  We don't have a part number or datasheet for his bridge, but the per-diode current would be 25A if the system is balanced.  Even if the Vf were 1.0V at that point, it still is 50W, not 100.  And we don't know if he used an actual single-module bridge, do we?  Unless his motor controller produces huge transients, these would work--and two cost less than any of the 1kV 100A bridge modules I can see.

https://www.mouser.com/datasheet/2/240/DSS2x101-02A-1549178.pdf

[Siwastaja]

Even 20W would be enough to set a cell in thermal runaway if placed at unfortunate position right next to the pack. The problem I'm seeing he's not even considering this, claiming repeatedly that his diode hack is definitely fine and conservative.

Obviously this is just one possible failure mode, not the most probable root cause.

I have witnessed Chinese pack BMS power MOSFETs designed completely ignoring thermal design, dissipating some 20W at rated currents, placed right next to the cells, so the same could be happening by this manufacturer, or by mr. Rossmann himself in form of the diode hack.

[bdunham7]

Even 20W would be enough to set a cell in thermal runaway if placed at unfortunate position right next to the pack. The problem I'm seeing he's not even considering this, claiming repeatedly that his diode hack is definitely fine and conservative.

Sure, 20W could cook a cell if you really tried, but I'm just not convinced that is all that likely since there's a more likely culprit here.  The statement he made that caught my attention was something to the effect that since each cell can 'conservatively' put out 8 amps, then a 20S10P pack can put out 80 amps 'conservatively'.  With perfectly matched and balanced cells in a pack that is temperature controlled, that might be sort of true, although not 'conservatively' as I would use that term.  In this case, I would suspect that mismatches in current flow simply overstressed a cell or cells and they didn't react well.

[SilverSolder]

Not quite the same as a turbo 'busa you also have the kawasaki ninja h2 which is a factory supercharged bike with ~310hp and 115lb-ft torque.

I would call that adequate performance, for a commuter bike! 

[Gyro]

... In this case, I would suspect that mismatches in current flow simply overstressed a cell or cells and they didn't react well.

Actually, given the intensity of the fire, I would say that they reacted very efficiently! 

[Siwastaja]

here.  The statement he made that caught my attention was something to the effect that since each cell can 'conservatively' put out 8 amps, then a 20S10P pack can put out 80 amps 'conservatively'.  With perfectly matched and balanced cells in a pack that is temperature controlled, that might be sort of true, although not 'conservatively' as I would use that term.  In this case, I would suspect that mismatches in current flow simply overstressed a cell or cells and they didn't react well.

Yes, he really likes the word "conservative", yet has absolutely no idea about battery tech. Samsung 35E is a high energy density cell, not a power cell; their use is in laptops and similar, where long runtime is necessary; as a result, the DC resistance is a compromise. Anyone who have designed with li-ion cells know these cells are normally discharged at 1.0C max, maybe at 2.0C for a short peak. If higher discharge rates are needed, power cells such as Samsung 29Q (if I got that right) are available, these are used in power tools. A conservative design would rate the 35E some 5A max peak and 2.5A max continuous.

Look at what Tesla is doing with standard 18650 COTS energy cells (originally; now they have their own cells); the whole key is staying well below 1C discharge on average, and only go to 2C short peaks, and carefully increase the peak power while adding liquid cooling, monitoring, and own research verifying the cells can take it.

Do note, it can be a combination of issues. Having overstressed the cells they can be already heated to near 100 degC, in which case having a hotspot electronics (The Full Bridge Rectifier^tm, or the Chinese BMS power switch MOSFETs) close wouldn't need to put that much extra heat in.

Or, the root issue might be just counterfeit cells.

[tszaboo]

Even 20W would be enough to set a cell in thermal runaway if placed at unfortunate position right next to the pack. The problem I'm seeing he's not even considering this, claiming repeatedly that his diode hack is definitely fine and conservative.

Sure, 20W could cook a cell if you really tried, but I'm just not convinced that is all that likely since there's a more likely culprit here.  The statement he made that caught my attention was something to the effect that since each cell can 'conservatively' put out 8 amps, then a 20S10P pack can put out 80 amps 'conservatively'.  With perfectly matched and balanced cells in a pack that is temperature controlled, that might be sort of true, although not 'conservatively' as I would use that term.  In this case, I would suspect that mismatches in current flow simply overstressed a cell or cells and they didn't react well.

He is completely ignoring the fact, that a battery built out of cells, might have different rating than the cells. BMS and all. And has no idea what the difference between the words cell and battery.

[tom66]

Rossmann is a perfect DK example.  He's very knowledgeable when it comes to iPhone/Macbook repair,  and can understand some circuits,  but he's no clue about other things -- and this is one example.

What I don't get is why is the bridge rectifier there in the first place?  OK, if you need more range, why not just have a change-over switch that the operator can use?  Perhaps it's not a seemless discharge of two packs but I highly doubt the bridge rectifier would result in that anyway.

The fire probably occurred because the pack got hot, but with the air cooling from the cycle ride it stayed within reasonable temperatures.  Then it is parked up but still with a hot battery.  There is a reason many EVs use liquid cooling, that runs after the vehicle is parked on hot summer days, and it is to prevent a catastrophic failure like this from occurring (it also no doubt helps extend the lifespan of the pack).

[Siwastaja]

He should have just bought a bigger pack instead of kludging with pack paralleling.

(This may or may not be related to the fire.)

[nctnico]

He should have just bought a bigger pack instead of kludging with pack paralleling.

Parelleling packs using a bridge-rectifier-ish solution is not uncommon. Nothing new here. At some point a bigger pack gets too bulky or too heavy. However parallelling should only serve to increase capacity, not current rating because you can't be sure that each pack delivers the same amount of current in every situation. And for sure diode dissipation is an issue. If you want to design conservatively then assume a drop of 2V per diode. Chances are the bridge rectifier overheated and shorted out.

The most likely answer is that one of the packs had a defect and it caught fire as you already suggested. After all a battery pack should have a current limit to prevent over stressing the cells.

[Bud]

Extra like for the zombie firefighters in the video.

[Halcyon]

I know this is an old thread, but the update is worth a mention.

Effective January 2024, the UK Government has banned the sale of Chinese-based UnitPackPower Lithium Ion battery packs as they present a serious risk of fire, are poorly built with non-existing/insufficient overheating protection and battery management.

It's actually quite shocking (but not unexpected) that an unscrupulous company like UnitPackPower think they can get away with their lies, deceit and just generally shitty products.