LiPo batteries: the terms the rules use, and the hazard bodies describe.

Cell count and voltage, as racing rules write them

No standard was found that defines the hobby's "S" cell-count label or its "C" rating, so this site uses those terms only as racing rules use them, and gives no C ratings. The FAI's own figures show how its cell count works: at 4.25 V a cell, a 4S pack may reach 17 V and a 6S pack 25.5 V.

The FAI's 4.25 V and MultiGP's 4.35 V are two bodies' rules for their own races, not a disagreement about the batteries, and they are never combined here; the same goes for the AMA's 2016 recommendation. FAI figures are from the 2025 edition; the 2026 edition was not read (its effective date is reported as 1 January 2026 and as 1 June 2026). MultiGP figures are from its class page, read 30 October 2026; its Rule Book was not read.

At an F9U event, rule C.4 lets the organiser check each registered model's battery voltage, and under rule C.7.4 officials may stop a flight when a model no longer meets acceptable safety standards, giving a dangling battery as an example.

The terms air transport rules use

IATA's passenger guidance of 31 March 2026, based on the 2025-2026 ICAO Technical Instructions and the 67th edition of the IATA Dangerous Goods Regulations, uses different measures:

• Lithium-ion: a secondary (rechargeable) battery in which lithium is present only in ionic form in the electrolyte. Limits for these are set in Watt-hours; non-rechargeable lithium metal batteries are limited by lithium content in grams.
• Watt-hour (Wh) rating: the rated capacity in ampere-hours multiplied by the nominal voltage. IATA says all lithium-ion batteries are required to have the rating marked on the outside of the case, and if staff cannot verify it from the battery or its documents the operator may refuse to carry it.
• Spare battery: a single-cell or multi-cell battery designed to be inserted into or attached to a specific device. In the 2026 guidance, power banks are no longer called spare batteries.
• UN 38.3: every battery carried by passengers, or shipped as cargo on a passenger aircraft, must be of a type that meets the UN Manual of Tests and Criteria, Part III, subsection 38.3.

The IATA guidance, re-read for this site on 30 October 2026, defines lithium-ion and lithium metal batteries and does not mention lithium polymer by name. This site does not say which of IATA's categories a particular pack falls into. The limits themselves are on flying with batteries.

The hazard, as a safety body describes it

No fire-service or NFPA page specific to drone LiPo batteries was found. The fullest description read is a 2023 Underwriters Laboratories (UL) fact sheet on lithium-ion batteries, distributed by the New Jersey Division of Fire Safety. In summary, it says:

• lithium-ion batteries can overheat, catch fire and cause explosions, most commonly when damaged, subjected to electro-chemical abuse (overcharging or completely draining are its examples), exposed to high or low temperatures, or affected by an internal short circuit;
• thermal runaway, a self-heating process in a cell, is the primary driver of the risk, can exceed 1,000 degrees F, breaks the cell down into smoke and flammable and toxic gases, and can spread to other cells;
• runaway often ignites a fire at once, and where ignition is delayed, a build-up of flammable gases can cause an explosion;
• from the first sign of trouble a person may have less than a minute to escape;
• it advises choosing products listed or certified by a nationally recognised testing laboratory, and says many products sold online do not meet those standards.

A secondhand mailing-list copy of a New Zealand fire-service statement gives a higher figure, over 1,000 degrees C, for lithium-polymer fires. That original was not found, so the figure is unconfirmed and differs from UL's. More on battery fire risk.

Another published record this site's research found is the US Consumer Product Safety Commission's recall notices, for example recall 08-364 (19 August 2008), in which the CPSC stated that radio-controlled helicopter LiPo batteries could overheat and catch fire while charging. See recalls.

Standards named, not read

Search summaries of UL's pages say UL describes UL 3030, its standard for unmanned aircraft systems, as covering electrical system requirements for commercial drones flown by trained pilots, and names UL 62133-2 and UL 2054 among battery standards relevant to drones. A search summary of ASTM's store lists a work item to revise ASTM F3005, the specification for batteries for small unmanned aircraft systems. None of these texts was read, and none is presented here as applying to any racing battery.

Batteries and the FCC Covered List

In the United States, the FCC's fact sheet of 7 January 2026 names batteries and battery management systems among drone critical components on its Covered List, and also says generic batteries and similar parts that never needed FCC authorisation do not newly need it. See the FCC Covered List.