E-bike battery fires and how to stop them

A rise in fires involving e-bike batteries recently prompted the London Fire Brigade to issue a warning, urging people to only use trusted batteries and be careful to charge and store them correctly. asecos’ Les Day explains the risks and how storage cabinets can protect against fires and explosions

What are the risks with e-bike batteries – what should bike shops be aware of?
The major problem with lithium-ion batteries is that they can go into what’s called “Thermal Runaway”. This is a process that starts in one cell in a battery, leading to a temperature increase that results in the cell disintegrating, suddenly releasing its stored energy.

This release creates a domino effect, causing adjacent cells to also disintegrate, release even more energy and further increase temperature. The result of this chain reaction can be very unpredictable. It can be a rapid explosion, or a slow smouldering fire with occasional flare-ups.

Lithium battery fires are no joke. Not only are they difficult to extinguish, but also release a lot of very harmful by-products, such as hydrogen gas, which is highly flammable; hydrofluoric acid, which is corrosive and extremely toxic; and oxygen, which fuels and sustains the fire.

What can e-bike owners do to keep safe?
Well, I think the first thing they need to understand is what can cause Thermal Runaway. There are three main reasons:

Electrical overload
Faulty charging due to cheap chargers, damaged cables or a malfunctioning built-in battery management system

Mechanical damage
Impact or penetration – for example, a battery can be struck by a foreign object whilst cycling

Thermal overload
Overheating caused by things such as a fire nearby, side effect of charging too many batteries in a small space…

The biggest issue I see here is that, unless there is obvious damage to a battery casing, they can be invisible. Think about a scenario where a customer brings a bike in for service – the service agent has no idea how that battery has been treated, no idea if cheap imported chargers have been used, or whether the battery itself is a cheap import.

Therefore, they have no idea what they have on their premises and are unshielded from the risks. This is why they need to consider a safe storage solution – if thermal overload occurs, they need to prevent that fire from spreading to the surroundings.

Tell us a bit about the e-bike storage cabinets and how they can protect against any fires or explosions.
The first thing asecos considered was the battery storage concept. We’ve drawn on over 25 years’ experience in manufacturing cabinets for hazardous materials and have concluded that the concept had to be based on supervision, detection, suppression and evacuation.

Supervision is really the first step and essential to the success of the concept. Eyes cannot be kept on stored batteries 24/7, so it’s vital that we have a system in place to alert us of any issues. This is particularly important where active storage is concerned as many people adopt “unsupervised charging”, where batteries are placed on charge out of hours or out of sight.

This means that if there is a faulty battery, we need to know about it as quickly as possible, then the fire must be suppressed long enough for the emergency services to evacuate the battery to a safe location where it can either burn out completely or where effective extinguishing is possible.

Based on these principles, asecos has developed the ION Line range, which now consists of six models. Two for passive storage (storing only) and four for active storage (storing and charging). Safe “active”  storage is important as it allows for unsupervised charging of batteries. All of the models have one thing in common; they are fire-resistant for 90 minutes both from the outside-in and the inside-out.

Why is this important? Well, the stored batteries need to be protected from a fire outside the cabinet as this could lead to thermal overload. However, a fire is more likely to start within a battery, so we need to contain it within the cabinet. Also, depending on the model, cabinets may be fitted with smoke detection, temperature sensors and fire suppression along with a warning system to alert you to any problems…

Why should bike shops consider a storage solution?
It is clear from the regular reports in the media and bulletins issued by the likes of the London Fire Brigade that lithium-ion fires occur with increasing regularity and are very real dangers.

If a problem occurs with a battery and you are in the vicinity of such an incident, you may have time to react and do something about it, but because of the ferocity of these fires, that may simply mean evacuating the premises and calling the fire services.

The extent of the damage in these circumstances is unforecastable, but a fire at a bike store in Hanover resulted in €0.5 million of damages, as the fire quickly spread to a multi-storey car park above the store. You may get lucky, but take this a step further – what if this happens overnight or at a weekend when the premises are empty.

It will almost certainly be too late unless you have invested in a safe storage solution, preferably one that can be connected to a building alarm system or provide a mobile alert to make you aware of an issue.

We really believe that it’s vital that you take steps to make your workshop safe from the effects of Thermal Runaway. If you’d like more information on asecos products, please contact your Madison sales agent.