EUC storage & charging cabinet with fire suppression system

[Seba]

We all know the risks associated with a lithium-ion battery fire. Every once in a while there are reports of someone's battery catching fire while riding, while charging or even while in storage. The problem with Li-Ion cells is that when they get heated to a certain temperature, a thermal runaway begins, in which heat and flammable gases are generated. It is a self-sustaining reaction in which the generated heat leads to the ignition of the gases produced and lasts until the cell burns out completely. One cell is able to heat up adjacent cells, which results in a chain reaction. As the batteries used in electric unicycles often have a capacity exceeding 1000 Wh, a fire of such a battery is a very serious threat. Especially, when we have several wheels that are stored in the same room (like garage, as in my case).

Because last time there were some tragical events with wheels catching on fire, I finally decided to build a safety cabinet that could protect my garage (and entire house) from a fire caused by a battery problem. Some of my wheels are very old and the battery may fail at any time. Also, sometimes I get wheels for EUC World testing. Wheels, that are a one big unknown to me. I don't know if they were handled in a correct way, id their batteries are OK etc. So here is the result of my work - a safety cabinet for EUC storage & charging, equipped with automatic fire suppression system.

Before I'll write more details, some of you may need some information about lithium-ion batteries. Despite their name, they don't contain metalic lithium that could react with water. More, using water to fight Li-Ion battery fires is now a golden standard and water is the most effective agent used by professional fire brigades around the world. For those interested in details, here are interesting documents:

https://www.mdpi.com/1996-1073/13/19/5117/pdf

https://www.aidic.it/cet/18/67/122.pdf

https://publikationen.dguv.de/widgets/pdf/download/article/3926

You can find more by querying Google. And if you want to convince me that water isn't a right agent for fighting Li-Ion fires, please - DON'T  Ok, let's go for the details.

As a base, I used standard, reinforced low-height metal cabinet for use in workshops in which I have installed an automatic water extinguishing system. Additionally, inside the cabinet there are two 230V AC sockets to supply battery chargers. The power supply can be switched on and off remotely, via the local network or via the Internet. In the same way, it is possible to monitor the cabinet, including remote activation of the extinguishing system.

The heart of the extinguishing system is the sprinkler line, equipped with four full-cone nozzles, which ensure adequate coverage of the entire volume of the cabinet with water mist, including the cooling of its walls. Inside the cabinet there is a smoke sensor and two temperature sensors. Smoke detection or an excessive increase in temperature inside the cabinet causes the valve to open, which starts the process of extinguishing and cooling the wheels and batteries inside the cabinet. At the same time, the power supply to the charger sockets located in the cabinet is disconnected. The water feed to sprinkler line is monitored by a pressure sensor. The cabinet's water installation is supplied from the house's water supply system.

I used a special bistable valve to control water feed into nozzles. This means that a short pulse powering the coil is enough to open it. In the event of a control failure, power failure, etc., the valve remains open, which ensures continuity of water supply in a fire situation. In a water installation, pipes and fittings are connected by brazing (using silver). The "brain" of the whole cabinet is controlled by the Siemens LOGO! 8 programmable controller. Emergency power is provided by a 12V 7Ah VRLA battery which keeps system running in the event of a power failure.

The cabinet I used is neither particularly strong nor airtight, and this is intentional. It is designed to allow the unobstructed egress of water, which can then be drained off through a drain in the floor. Cabinet door not being airtight also prevent the pressure surge in the cabinet and a possible explosion. The cabinet, cooled with water sprayed on its walls, should easily prevent fire from spreading outside for at least some time. It can certainly give you the time it takes to call the fire brigade and get there. Especially that the control system can be connected to the building's alarm control panel, so that if a fire is detected in the cabinet, a fire in the building is signaled at the same time. And because the alarm control panel is integrated with the building automation, it is possible, for example, to automatically open the garage door.This allows not only efficient ventilation, but also facilitates the access of the fire brigade.

I know that for many of you it may be an overkill. All the components and materials costed me about 1200 EUR. It's less than a medium-sized wheel. As a result I got a sense of security, something that is hard to express in terms of money. And I know that people that already experienced a EUC fire will know what I mean. It's just like a insurance - you pay for it, but most of us will never get anything for it. Until shit happens...

[AtlasP]

As beautiful as to be expected from the same mind that created/maintains EUC World. Well done.

[EUC Forest]

Awesome design, bravo! I rely, rather more simply, on an auto fire extinguisher ball or two next to my wheels and other lithium batteries. Better than nothing.

[DavidB]

Very slick. I like the automatic garage door opener option. I was reading a pdf the other day about the gases from these events and was shocked at just how toxic they are. Everyone knows they are to be avoided but the lethality within a confined space was extraordinary.

[Chriull]

16 minutes ago, DavidB said:

I was reading a pdf the other day about the gases from these events and was shocked at just how toxic they are. Everyone knows they are to be avoided but the lethality within a confined space was extraordinary.

Number one lethality of beeing with something burning/(heavily) smoking should be the lack of oxygen. Maybe supported by carbonmonoxide.

And some passing out from catbondioxide before dying...d

Additiinally i'd consider fumes from about almost eberything in a household like electronics, plastics, ... as extremely toxic.

Or is there something even worse within the li ion batteries?

[DavidB]

Yes HF.

1.7 mg/m3 Allowed exposure level at work in Sweden

25mg/m3 IDHL

139mg/m3 The lethal 10 minute value ((AEGL-3)

A fire that consumes a 2kw li-ion battery emits b/w 40 and 400gm of HF according to this pdf. That would be 40000mg/90m3 for a 6mx6mx2.5m garage. That is 444mg/m3 or 3 times the lethal 10min level at the lower emission and 10x that (ie 30x lethal dose) at the higher level.

Like I said in my previous post I was shocked by the data.

 The pdf is "Thermal propagation in lithium ion batteries" at ec.europa.eu page 16 on..

The same pdf stated that if the gases released from pre-ignition venting are confined an explosion can occur on ignition. I have no idea how probable this would be. But LTO batteries are looking like the weight may be a acceptable trade-off when considering there high discharge rate and fast charging.

[Seba]

A short video from a test run of fire suppression system:

This was initiated manually from control panel. This test proved design assumptions - water spray discharge at ~20 liters per minute under water supply of about 2.2 bar (1.5 bar at sprinkler line)