556 fires in three years, six dead and a call-out every other day. We speak to the firefighters and doctors struggling to cope with a deadly new epidemic.
Not UK, but I live my bike. But its battery does scare me. Lithium is dangerous, and I often worry about it causing a fire.
What kind of things can one do to protect themselves, or reduce the risk of then catching fire?
Afaik these fires are from dodgy cheap imports or diy mod jobs. If you’re buying a reputable brand from a reputable supplier, then as long as you’re following the instructions, you should be fine.
It is not the lithium that is the problem, it is the sheer amount of energy stored in a tiny space.
Not quite. Lithium ion batteries have 2 advantages. Massive capacity (per kg) and a very low internal resistance. The latter is amazing for getting bursts of power, with little to no voltage sag. Unfortunately it’s also the reason failures are so spectacular.
A lithium ion battery can dump a huge amount of energy (internally) in a short time. This leads to spectacular amounts of heat and fire. Other lithium chemistries are not so volatile.
E.g. lithium iron phosphate batteries have a small hit to capacity (about 80%) and a lower peak current. Their ability to self destruct is far less.
In short, it’s the combination of the amount of energy and how quickly it can dump out in a failure mode.
I feel bike batteries don’t need to dump power quickly due to their nature, but I have been wrong before.
They need a moderate spike to get the motor moving, then a steady current to keep it going.
E.g. my ebike is 250W @ 36V. That’s 7A at full (continuous) power. A lithium ion battery can be discharged at around 10C while a lifepo4 battery can only do 1C discharge. My 13Ah battery could handle it, even with the 20% capacity loss at 0.67C (7/(13*0.8)). A 500W version would exceed the battery rating however, if it’s lifepo4, while being fine with lithium ion.
Basically, lifepo4 batteries could handle a low end ebike, but would likely still want some super capacitors for spikes. They would need to scale up significantly in size to handle more powerful motors.
Oh im learning something! Ill look into this!
It’s this, combined flammable electrolyte used in NMC chemistry (the most energy dense “standard” chemistry) which make the batteries vulnerable to catastrophic failures. LFP batteries have lithium and high energy density, but are significantly safer because thermal runaway won’t cause then to actually catch fire from the inside out. They can still start fires if a hot mound of melting battery makes contact with flammable things, but the standard image of “jets of flames shooting out of a battery assembly” simply won’t happen.
Fair enough.
Then they are using the wrong lithium-chemistry, as others here have noted.
You can see the fire-risk/non-risk for different chemistry-types here: https://www.batteryuniversity.com/article/bu-205-types-of-lithium-ion/
All they actually need to do, is outlaw the most-dangerous chemistries, while leaving the safer ones.
LiFePo4 or whatever that one’s called, is a good standard.
Lithium Titanate costs waaay too much, & is low-power-density, but … for aviation ( starter-batteries ), it’d possibly be saner.
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This is a solved problem. LFP does not use flammable electrolyte, but it’s like 10% lower energy density, so the obsession with range and “built in” batteries makes it a non starter for stat shoppers who only compare the top line numbers.
Can you spell this out for the non ebike obsessed? I’d like to know the differences (because at some point I’m going to be too old for my push bike.)
When people shop for an e bike, they look at two main things - speed and range. For a given battery volume, NMC will have the best range and highest discharge rates, so manufacturers know using anything else puts them at a competitive disadvantage on those two top line numbers. Very few manufacturers even offer LFP because the subtlety of “you are sacrificing 10 miles of range, but it is virtually impossible for the battery to start a fire” is simply too complicated. I mean, the vast majority of ebikes don’t start fires, so if you are going to spend $2k on one, you are going to get the best paper stats you can.
Ah. Got it.
LFP? NMC? What is the safest battery out there?
