Battery fire risk, as regulators and fire services describe it.

What this page rests on

The research behind this site looked for a regulator, fire service or standards body publishing guidance specific to the batteries in RC racing cars, and found none. What follows comes from the US Consumer Product Safety Commission (CPSC), whose 2008 alert and earliest recalls concern RC aircraft rather than cars; the US Occupational Safety and Health Administration (OSHA); a general lithium-ion fact sheet from Underwriters Laboratories (UL), dated 2023 and hosted by the New Jersey Division of Fire Safety, which does not mention RC models; a 2009 advisory from US transport regulators; and two UK fire services.

The CPSC alert is about helicopters and planes

The CPSC's consumer alert 08-189, dated 12 February 2008, has a narrower subject than RC batteries in general. It warned of what it called an emerging fire hazard from the battery technology in remote-controlled helicopters and airplanes, saying rechargeable lithium batteries can overheat, catch fire or explode if overcharged. It recorded 26 reports since November 2007 of RC helicopters igniting while being charged and one igniting in flight, with minor burns and minor property damage.

The alert explains that makers use lithium batteries in such toys because they are light and hold a lot of energy in a small package. It refers broadly to remote-controlled toys with rechargeable lithium batteries, but it never names RC cars. It also says battery charging should be done by adults. Its remaining advice is a procedure and is not repeated here.

Two CPSC recalls from the same period also concern aircraft. Recall 07-139 (27 March 2007) covered about 66,000 radio-controlled airplanes with lithium polymer batteries that the CPSC said can overheat while recharging; it recorded nine overheating reports, including one plane catching fire and a minor burn. Recall 08-364 (19 August 2008) covered lithium-polymer batteries sold with an RC helicopter kit, which the CPSC said can overheat and catch fire while charging and ignite nearby combustibles. These show how the regulator frames the hazard in hobby RC products; they say nothing directly about cars.

What OSHA says about thermal runaway

OSHA's lithium-ion battery page (no publication date shown) groups the hazards as chemical hazards, stored electrical energy and thermal runaway, and says they can arise during manufacture, use, transport, emergency response, disposal and recycling. It describes thermal runaway as a chain reaction: heat from one failing cell damages the cells next to it, and because the battery combines a flammable electrolyte with a large store of energy, the result can be fire, explosion and the release of chemical by-products.

OSHA lists the causes as internal short circuits from manufacturing defects, mechanical damage, excessive heat or cold, and improper charging. It says battery components can be flammable, toxic, corrosive or reactive, and that the salt lithium hexafluorophosphate can react with water to form hydrogen fluoride. Among the products of thermal-runaway fires it names hydrogen fluoride, hydrogen chloride, hydrogen cyanide, phosphoryl fluoride, carbon monoxide, carbon dioxide, black carbon and other particulates. Possible signs of thermal runaway, in OSHA's list, are a rise in battery temperature, fire, or venting of gas, vapour or smoke.

What the UL fact sheet says

The UL fact sheet says lithium-ion batteries most commonly overheat, catch fire or explode when they are damaged, when they suffer what it calls electro-chemical abuse (overcharging or draining completely are its examples), when they are kept in high or low temperatures, or when an internal short circuit occurs. It calls thermal runaway the primary driver of the risk: a cell heats itself, generating more than 1,000 degrees Fahrenheit, and breaks down into smoke and flammable and toxic gases, with the heat able to spread to other cells.

The fact sheet says thermal runaway often starts a fire immediately, and that if ignition is delayed, built-up gases can explode and spread fire through a building. It says a person could have less than a minute to escape from the first sign of a problem. Its warning signs are swelling or punctures, unusual hissing or popping, excessive heat or a strange smell, and white or grey wispy smoke, which it treats as a sign of immediate danger. It also recommends products listed or certified by a nationally recognised testing laboratory and says many products sold online do not meet those standards.

Two temperature figures

The figures in circulation differ. The UL fact sheet gives more than 1,000 degrees Fahrenheit. NTSB safety recommendations hosted on the FAA's website are summarised in search results as saying a cell in thermal runaway can reach 1,100 degrees Fahrenheit or higher; that document was not read, so the second figure is unconfirmed.

What US transport regulators said

PHMSA and the FAA, in safety advisory notice 09-05 (issued 29 September 2009 and published in the Federal Register on 7 October 2009), said lithium batteries are hazardous materials because they carry chemical hazards, such as flammable electrolytes, as well as electrical hazards. The advisory said defective, misused, mishandled, badly made or overcharged batteries can overheat and ignite, that overheating can lead to thermal runaway, and that once ignited such fires can be especially hard to put out. It counted over 40 air-transport lithium battery incidents since 1991. Current carriage guidance for lithium batteries, as IATA states it, is on travelling with batteries.

What fire services record

No fire service count of RC-car battery fires was found. Asked in 2023 for household fires caused by lithium-ion batteries in toys, toothbrushes, phones and laptops, the London Fire Brigade said it could not break its data down by those items (Freedom of Information response 8060.1, 24 November 2023). The same response counted London household fires with the ignition source "batteries, generators" or "battery charger" as 78 in 2021, 77 in 2022 and 69 from 1 January to 30 October 2023. Those totals cover every kind of battery item and are not RC figures.

Single incidents appear in fire-service reports. Essex County Fire and Rescue Service reported that on 27 October 2021 a remote-control car battery overheated and exploded while on charge in a house kitchen in Marks Tey and caught fire; no people or animals were hurt. A crew manager noted that the occupants believed they had bought genuine goods and said it can be hard to tell when buying online. In the United States, press reports have attributed a garage fire in Everett, Washington, and a basement fire in Lone Tree, Colorado, to RC-car batteries on charge; the fire departments' own releases could not be read, so those accounts are unconfirmed.

Recalls of RC vehicle batteries and parts

CPSC recall notices record specific faults, not how often batteries fail. Three involve batteries or a speed controller in RC vehicles: recall 07-101 (13 February 2007) of about 245,000 lithium-ion polymer packs for radio-controlled toy vehicles, which the CPSC said can ignite while charging; recall 13-227 (25 June 2013) of about 117 LiPo packs for micro RC vehicles, wired to the wrong connector terminals so that use or charging could cause overheating; and recall 17-139 (25 April 2017) of about 18,600 ready-to-run RC model vehicles in the US whose speed controller could short circuit, a fire hazard. Full details, with the regulator's wording and other countries' notices, are on recalls.

Batteries in the racing rules

The governing bodies treat batteries as a matter for rules. EFRA and IFMAR require hard-cased lithium packs from approved lists, cap the charged voltage per cell, and require a LiPo sack at their events, which they define in their rules as a receptacle built to contain a battery fire. That definition is the wording of a rule, not a test result, and this site does not present a sack or a hard case as preventing fire. Each body's requirements are set out on battery rules at events and battery rules by body.