Charging points for e-bikes and scooters in shared storage — installation requirements and fire safety

The guide on home batteries and energy storage systems covers the installation requirements for a stationary lithium-ion storage system. This article covers a related risk that occurs far more often in practice: daily charging of e-bike and scooter batteries in a shared bicycle or scooter storage room of an apartment building, and why the wiring and protection used for that purpose is often not designed for this load.

Why an ordinary socket circuit falls short here

A shared storage room typically has a limited number of wall sockets on one or a few circuits, originally intended for incidental use (a vacuum cleaner, a tool charger). When residents structurally connect multiple e-bike and scooter chargers to it at the same time, for several hours at a stretch — often via an extension cord or a power strip, because there are too few fixed wall sockets — a load pattern emerges that the circuit was never designed for: a sustained, continuous current over several hours, routed through connections (extension cord, power-strip connector) that are not rated for continuous duty and that, at a moderate contact resistance, can overheat precisely during that prolonged load.

The underlying battery risk: thermal runaway

E-bike and scooter batteries are, like a stationary lithium-ion energy storage system, susceptible to thermal runaway — a self-accelerating, runaway chemical reaction in a damaged or overcharged cell that can propagate to neighbouring cells in the pack (see the guide on thermal runaway in lithium-ion BESS for the underlying mechanism). An e-bike or scooter battery that has been damaged by a fall, water ingress, or use of a non-original charger that does not match the battery, carries an elevated risk of this, precisely while charging. The result is a very fast-developing, difficult-to-extinguish fire — a risk that is especially severe in a shared storage room because of the high density of combustible material present (plastic frames, other batteries, tyres).

What a properly designed charging point does differently

Fixed, individual charging connections instead of extension cords and power strips: each charging spot gets its own, permanently mounted wall socket connected directly to the circuit, so there is no extra transition resistance and no extra heat-generating point in the path that was never designed for continuous, multi-day duty.
Enough circuits for the actual number of charging points: the number of e-bikes to be charged simultaneously is established at the design stage, and the circuit layout and main fuse are sized accordingly, instead of continuing to rely on a number of circuits intended for incidental use as the number of residents with an e-bike grows.
RCD type matched to the charging profile: a smart charger for lithium-ion batteries can, like an EV charging point, introduce a smooth DC component into the fault current during an internal fault that a standard type A RCD does not detect (see the guide on RCD types AC/A/F/B and the guide on RDC-DD detection at charging points for the underlying principle used at EV charging infrastructure). When the DC behaviour of the chargers in use is uncertain, a type B RCD — or a type A RCD combined with a separate 6 mA DC fault-current detection device — is the safer choice over a bare type A RCD.
Physical and fire-related separation: the charging spot is preferably not placed directly beneath an escape staircase or in a narrow escape route, and is kept separated as much as possible from large quantities of other combustible material.

Note: this is a relatively new and rapidly evolving area for which no fully crystallised, dedicated NEN 1010 section exists yet, unlike the one worked out for EV charging points (annex 722). The measures listed above are an application of the same underlying principles — sizing for the actual, continuous load pattern and RCD protection matched to the fault-current behaviour of the connected charger — to a new practical situation, not a literal quote from one specific standard clause.

Practical relevance

When assessing a bicycle storage room in an apartment building during a NEN 3140 inspection, or when designing a new charging facility, it is important to check whether the number and type of charging connections matches the actual, structural usage, whether fixed connections are provided instead of extension cords and power strips, and whether the RCD protection is matched to the possible DC behaviour of the connected chargers.

Common mistakes

Structurally connecting multiple e-bike chargers through a single extension cord or power strip on a circuit intended for incidental use, resulting in prolonged overload and extra transition-resistance points.
Not accounting for a possible DC component in the fault current of a smart charger when selecting the RCD type, even though this is exactly the same principle as with an EV charging point.
Placing the charging spot directly beneath an escape staircase or in a narrow escape route, so that an incipient battery fire blocks the escape route before residents can leave the building.
Not scaling the number of circuits with the number of residents with an e-bike or scooter, so that a facility that was originally more than adequate gradually becomes structurally overloaded.