Safety on the DC Side and the AC-Only Standard

The incident record

No safety incident specific to a pedal-powered cinema was located in any public source. That record is bounded by what has been published and searched. The nearest quantified record sits one domain over, in lithium batteries on bicycles: London Fire Brigade recorded 206 e-bike and e-scooter fires in 2025, a record high, and UK product-safety notifications trace 45% of such fires to post-market conversion kits ^1,2. A pedal-cinema rig shares the ingredients — high-current DC, lithium storage, long public cable runs, often assembled by non-specialists rather than electricians.

Specifications

What do these labels mean?

Field	Value	Confidence	Sources
London Fire Brigade e-bike/e-scooter fires, 2025	206 incidents (record high)Adjacent-domain quantified risk record; no pedal-cinema-specific incident was located in any public source.	Documented	¹
UK product-safety fire-cause attribution, 2024	45 % of e-bike/e-scooter fires traced to post-market conversion kits	Documented	²
Reverse-current diode rating, Low-tech Magazine build	10 A, against an 8–9 A maximum production current"Without a diode, the battery could power the generator (and turn the pedals) instead of the other way around."	Documented	³
Rock the Bike minimum cable gauge for exposed power runs	14 AWGAlongside per-branch fusing, locking connectors, strain relief and enclosed circuitry.	Documented	⁴
KLAK state-of-charge alarm and cutoff thresholds	20% and 95% alarms, 100 % cutoff; auto-shutdown after 10 minutes without pedalling	Documented	⁵
BS 7909 scope statement	"Direct current supplies are outside the scope of this British Standard"Verbatim; BS 7909 covers low-voltage AC only.	Documented	⁶
Ingress-protection (IP) rating disclosure across operators	not disclosedNo operator in the research publishes an IP rating for pedal-generation hardware.	Not disclosed	^7,5
Electric Pedals weather restriction	"cannot operate in heavy rain or high winds"	Documented	⁷
German event-cabling guidance	DGUV Information 215-310; DGUV Vorschrift 17Cables must be routed off traffic paths or secured with bridges, tape, or overhead routing.	Documented	^8,9
Electric Pedals hire package	risk assessment, public liability insurance, and 2 staff bundled into every hire	Documented	⁷
KLAK liability and medical-caution wording	"Nutzung auf eigene Gefahr" (use at own risk); medical caution for weak circulation or heart conditions	Documented	⁵

What BS 7909 covers

BS 7909, the UK code of practice governing temporary electrical systems at events, states its scope: "Direct current supplies are outside the scope of this British Standard" ⁶. German DGUV event guidance addresses the same territory — cable routing, earthing, the 230 V side — and likewise stops upstream of the inverter ⁹. The pedal-to-buffer DC chain in every documented system therefore sits outside any event-electrical standard written for the purpose, and "meets BS 7909" cannot cover the generation side of a pedal cinema. Until such a standard exists, the DC bus needs a qualified electrical review of its own.

Diagram of an event electrical system with the AC side inside the standard's scope and the DC generation bus outside it — Scope graphic: BS 7909 covers the AC side; the pedal DC bus sits outside^6,3,4,5,8,9 Image: BicycleCinema.org, drawn from the research corpus

Three documented layers of protection

In the systems documented in technical detail, protection comes in three layers. Reverse-current isolation: Low-tech Magazine's build manual warns that "without a diode, the battery could power the generator (and turn the pedals) instead of the other way around" — a hazard once any buffer sits behind a permanent-magnet generator — and specifies a Schottky diode rated above the expected current, 10 A against an 8–9 A maximum ³. Overcurrent protection and cabling: Rock the Bike fuses every bike branch individually, noting that input cables "are long and are often subject to harsh conditions: people walking on them, tripping over them," and specifies a 14 AWG minimum for exposed power runs alongside locking connectors, strain relief and enclosed circuitry ⁴. Supervision: KLAK's central unit alarms at 20% and 95% state of charge, cuts off at 100%, and shuts down after ten minutes without pedalling ⁵; Rock the Bike's controller disconnects pedallers on overvoltage ⁴.

Electric Pedals night screening in a courtyard between brick buildings: audience seated before the screen, LED-lit pedal bikes along the right — Photo: Electric Pedals (electricpedals.com) — via electricpedals.com

Recommendations not yet fielded

Two further measures are not documented as built into any pedal-cinema system examined. Pre-charging or current-limiting an ultracapacitor bank matters because a discharged capacitor "appears as a short circuit" to whatever tries to charge it, drawing current limited only by internal resistance ¹⁰. Ideal-diode controllers offer a lower-loss alternative to a simple Schottky diode in a multi-bike array ¹¹. Neither appears in the KLAK, Rock the Bike, Cinécyclo, Oekotrainer or Electric Pedals hardware examined; both belong on a design-review agenda with a qualified engineer.

Mechanical and venue hazards

Pinch, crush and hot-roller hazards from stationary trainers are documented by insurers and manufacturers and mitigated by supervision and exclusion zones around moving parts ¹². German event guidance — DGUV Information 215-310 and DGUV Vorschrift 17 — requires cables kept off traffic routes or secured with bridges, tape or overhead runs ^8,9; KLAK's manual instructs that every cable crossing a walkway be gaffer-taped ⁵. Cable routing is the one area with an applicable standard rather than an adapted one.

Weather

No operator in the documented set publishes an ingress-protection (IP) rating for its pedal-generation hardware. Documented practice is avoidance: Electric Pedals "cannot operate in heavy rain or high winds" ⁷, and KLAK restricts operation to dry rooms or outdoor conditions with guaranteed dry weather ⁵. That is a scheduling answer, not an engineering one.

Risk transfer

Electric Pedals bundles a written risk assessment, public liability insurance and two staff into every hire ⁷. KLAK assigns responsibility to the event organiser — "Nutzung auf eigene Gefahr," use at your own risk — and adds a medical caution for participants with weak circulation or heart conditions ⁵.