There are no other fires quite like a lithium battery fire, and that explains why this category of product exists. Lithium-ion cells that fail do not go quietly. Falling into what is called thermal runaway, the failed cell continues to get hotter and generates its own combustion-supporting oxygen. Normal fire suppression is not effective. Water helps cool the cell, but a typical fire extinguisher will be useless. Battery cells are very good at helping their neighbors reach failure. That is why you will see a battery pack fail in staging, rather than all at once.
Lithium cells fail primarily due to overcharging, or cells that have been damaged in other ways (e.g. dropped, or punctured). This is why the greatest threat on a typical worksite is not a battery cell buried in a desk. It is the row of power tool batteries charging in an empty building, the staff e-bike, or the pallet truck plugged in by the storage racks. This is exactly what charging cabinets are designed to counter.
Functions of a Charging Cabinet
Good lithium charging cabinets do three separate functions all at once. They contain a fire, they detect one ahead of time, and they stop power from flowing to a faulty battery.
Containment is the headline figure. Better cabinets are rated for 90 minutes of fire resistance from the inside out. They have self-closing doors and fire protection seals to keep flames from spreading, as well as ventilation openings that seal with thermocouples. Ninety minutes isn’t an arbitrary number. It’s about the difference of the fire brigade dealing with a cabinet as opposed to a building.
Detection and cut-off are the the features that really get put to use the most. Smoke detectors are placed inside the cabinets, and charging that automatically halts if the doors open or heat is detected. On the better units, there is also a volt-free output that can be wired to the building’s fire alarm system.
Most ranges have a basic and a premium specification, and the difference is primarily in detection. A basic charging cabinet typically has the fire-resistant construction, socket strips, heat dissipation via a fan that activates during charging, and charging that stops when the doors open. The premium versions typically add smoke detection, power disconnection upon heat detection, and an external alarm connection.
The question that determines if the price is justified is whether or not there is a person present while the batteries charge. If charging is done overnight or on the weekend in an empty building, then detection and alarm features are doing a job for a person and are probably worth having. If battery charging is done during working hours with a person present, there is no need for more than a basic unit.
Single-phase or three-phase
The three-phase or single-phase distinction is relevant here because a lot of these systems are designed to power tools. Typical cabinets use a four-socket strip drawer that is 16A and 3500W with a 230V single-phase supply. That is good enough to power most tool chargers. But what about rapid chargers for large batteries? Those may demand a lot more than those single-phase strips. In that case, those cabinets are 400V three-phase with two strips. A good system is designed around the chargers. That’s key. A lot of these systems are modular. They may be anywhere from a small charging unit up to a full height cabinet with 24 charging bays. For one or two batteries, use the smaller modular units. For more than two, use a full height cabinet or a couple of those.
Storage cabinets are not charging cabinets
This distinction is tricky for some. Certain cabinets are configured for passive storage of lithium batteries, while others are for active charging. Since most incidents happen during charging, a cabinet must be fire-resistant and equipped with a managed power supply. If a cabinet contains only these features, it cannot have charging cables run through a door gap. This does happen though. If batteries will ever be charged in the cabinet, consider getting a charging cabinet instead.
Damaged and swollen batteries
A battery that is swollen, has been dropped, or crashed a battery-based transport is a new concern. This kind of battery has the potential to fail and combust at any given moment. Suspicion of this behavior demands a higher level of protection. Safety barrels, steel containers and fire protection transport boxes are some of the protective systems on the market. The transport boxes must be filled with packing materials that offer thermal insulation and cushioning to the battery in the unlikely situation that it fails. The best option is to transport the damaged lithium battery as quickly as possible.
What a damaged battery must not do is go in a general waste basket. A significant percentage of new circular disposal system waste fires are caused from lithium battery disposal.
What the insurer will ask
Insurers are becoming increasingly aware of lithium battery fires. So, at renewals and surveys, expect questions about battery charging. How many batteries do you have? Where do they charge? Is the charging contained and supervised? What do you do with damaged batteries? There is no explicit requirement for a cabinet. However, a response that reads “batteries charge overnight in a certified 90-minute cabinet that is wired to the alarm” will satisfy, and “they charge on a bench by the racking” will certainly spark a conversation. For the fire risk assessment, and for purposes of this conversation, it is a good idea to have the cabinet certification paperwork on file. Charging batteries should be an identified risk.
Does every site need one?
No. A site that has two drill batteries that charge on the bench during the day, with continuous supervision, is on the low end of the risk, and in that case a cabinet is likely an unreasonable expense. Risk increases with the number of batteries, unattended charging, larger batteries (e.g. e-bikes and ride-on equipment vs hand tools), and the increased severity of a fire where charging is taking place. A charging bench near racking in a fully stocked warehouse vs the same bench in a block-built store is a significant change in risk.
If charging is unattended, occurs in multiperson scenarios, or is done where a fire could reach stock or a structure, a cabinet is one of the less expensive fire protection systems a site can purchase. The fire service’s general guidance on lithium battery safety is worth a read alongside this — and the broader storage context is outlined in our fire safety and hazardous storage guide.