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E-scooter and E-bike battery safety - What is L2272, what is a safe battery and why does this matter when you are buying an electric scooter or electric bike? That is what this article sets out to discuss and answer. It's fairly long, approximately a 5 minute read, so strap in...
There has been a lot of news over the past five years relating to fires caused by low quality, electric bicycle and e-scooter batteries.
To be specific it is the advance of the high power lithium-ion power pack that has led to this: previous nickel-cadmium or lead acid packs did not tend to hold sufficient energy for serious 'thermal events' (as they are euphemistically known in the industry) to be a major issue.
When buying an electric scooter or an e-bike it is very important to understand exactly what the risks are and how you should think about your purchasing and maintenance decisions.
Firstly, to discuss the regulations and certification.
Recently certain cities including New York City started to ban the retail of batteries without UL2272 certification. This had a knock on effect - with insurers and building management companies starting to ban the charging of batteries without 2272 on their premises.
It is important to note that the UL2272 test itself does not itself make a battery safer - it is simply a certificate of confirmation that the battery has been designed, engineered manufactured to a safe standard. The tests cost between $10-20k to carry out (per paclk design!) which has always frustrated us slightly because we'd rather spend that cash actually engineering an even better battery.
I think this is important to emphasise because it is easy to imagine that UL2272 somehow adds a safety feature in and of itself.
That is not the case simply demonstrates that the manufacturer has followed good safety standards and was willing to have a laboratory confirm this with a stamp of approval.
So the real question is what actually makes a lithium battery 'safe'. What does that even mean?
We have to start with the cells, the building blocks of the battery pack. Battery cells for e-scooters tend to be small cylindrical objects with two names, 18650 or 21700. The first two numbers are the diameter of the cell in millimeters, the next two numbers are the length, and the final '0' simply indicates that it is a cylindrical cell.
So an 18650 is an 18mm x 65mm cylinder.
To create a battery cell three long strips, sort of like a roll of parcel tape, are stretched out and layered on top of each other. One of these layers is the anode, one is the cathode, and the third is called the separator. The job of the separator is to keep the anode and cathode separate - makes sense, really.
Once this threesome are laid up on top of each other they are checked for perfect alignment, then they are rolled into a small tight roll - Jelly Roll style - and inserted to a metal casing.
That is what creates the key components of a modern lithium ion battery cell.
The Devil's in the detail with this process. For example you have to be able to apply the anode and cathode and separator materials at a perfectly constant thickness down to fractions of a millimetre.
You also have to be able to ensure that there is absolutely no overlap which could allow the anode and cathode touch each other through the separator.
And you have to do all of this whilst also running thousands and thousands of miles of these materials through the machine, maintaining consistency of the materials consistency of the processes. It requires endless checking and quality controlling to be certain that everything is correct
So it is easy to imagine how a lower cost factory, attempting to create a lower cost cell, might consider loosening their standards on some of these expensive and difficult processes. Perhaps run the blades that trim the tapes a little longer, allow the rollers that the tape run through to get a little older. Much like budget airlines only taxiing with one jet engine to save fuel, squeezing every cent forces any supplier to push the margins.
In a good factory not only are all of these quality control processes extremely tight, but every battery cell also has its own QR code-style tag.
What that means is if the factory ever identifies an issue in a cell - for example, it will not maintain a proper voltage - then the factory is able to trace every single other cell that was manufactured in that batch, using those materials. That means they are able to check that there are no other quality control issues and can either remove those cells from the dispatch line - or if they’re proven to be in good condition can at continue to follow up and monitor once they are out in service.
By contrast the factories using budget cells have zero traceability and zero ability to understand where their cells come from. Often a factory assembling low-cost battery packs will have several cell suppliers. All of them depositing truckloads of untagged untracked cells unknown quality and unknown characteristics into a production hopper.
This garbage is then randomly assembled into packs, like a sort of battery russian roulette.
If that sounds unappealing, it gets worse...
When a budget factory is attempting to assemble low-cost battery packs for vehicles like e-scooters the first components they remove are the expensive monitoring and sensing devices. That means devices that sense cell voltage, check that different cells in the pack are balanced (e.g. behaving the same way) or that sense cell temperature.
They also remove the battery management system - the small computer that tells the monitors whether all of the cells are behaving as they ought to, both when discharging and when charging.
What this means is that ironically the budget cells which most need to be monitored - since they have low quality control standards - are actually the cells that also have the least monitoring.
Finally when attempting to assemble a low-cost pack, the tough external casings that should protect the cells and hold them in perfect alignment tend to be removed and replaced instead with a low-cost blue plastic shrink wrap.
When they even remove the case that is not a good sign
What does all this mean as a rider and owner?
We're all human - I'll readily admit that I've had my head turned by how extraordinarily cheap some lithium powered equipment seems to be. I recently trialled a couple of low cost battery hedgecutters in my own home, and Ive got to say while they can't hold a candle to Stihl or Milwaukee, for the cost they are genuinely impressive.
So while the appeal of low-cost lithium-ion batteries and the low-cost vehicles they enable us to buy is clearly high, it's important to appreciate the risk is also real.
When you charge or discharge any lithium-ion battery, the resistance in the wiring and inside of the cells themselves causes the materials to heat up, which also means it causes them to expand and contract.
The reason that is a problem is expansion and contraction cause movement. That can be movement between cell - or more importantly even within the cells it can cause movement between the three layers of anode, cathode and separator that we talked about at the start of this article.
In a low-quality cell that relative movement can be what leads to the anode and cathode touching one another across the separator, and it is that touching that leads to a short circuit and failure of the battery.
In a high-quality pack, this should be identified the battery management system computer. Early on in a potential failure it is designed to recognise that the cells are not behaving in a balanced way.
For example, one of the cells may start to hold less voltage, and that should lead the BMS to cut the power appropriately to ensure that it does not have an Issue
In the low-cost pack, because all of the sensing and BMS protections are removed it will just continue accepting power - even as that power leads to a potential risk of fire.
Having read this, you would possibly think why would anyone be so insane as to take these steps and produce battery packs of this nature.
To give you some sense of why there is an incentive to do this we need to talk numbers. When you buy a $500 electric scooter, the total Bill of Materials (cost from the factory) will be somewhere between $150-$200.
That means all the components, including the battery - motor - frame of the scooter - and every accessory like bells and grips and tyres.
110 individual components. There's a right way and a wrong way to make each one
The Bo battery on its own costs more to produce.
There is a very real financial benefit to people selling low cost, low quality battery packs.
In fairness, the vast majority of those go through their working life without danger. The more prevalent issue is that the pack loses its ability to put out lots of power and to hold a good amount of charge. This leads to reduced range and performance - this is known as battery fade.
At the end of the day if an E-scooter or ebike is just a very occasional play thing, if you are willing to keep the battery in a good state of charge, and if you have capacity to not charge it inside your property then these are not factors I personally would worry about.
We all have low-cost cells in our lives, whether in vapes, power tools or any of the other throwaway electronics that fill our world.
However if you are someone who takes pleasure in high-quality products, if you want consistent long-life performance, and if you do not have the facility to charge your vehicle outside of your property, then I would urge you to consider investing in high-quality products - which also means safer batteries.
If you're interested in reading more - Link to Articles
If you'd like to look at Bo M more closely - Link to Model M
If you'd like to read about The Turbo Land-speed scooter - Link to Turbo