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Batteries and chargers: the class sets the pack, the body's list decides it.

An electric racing car runs on a lithium pack whose cells, voltage and case are set by the class's rule book, and under EFRA's and IFMAR's rules only packs on that body's approved list may race. This guide names the categories and points to the rules; it gives no charging, balancing, storage or disposal steps. See also batteries and battery rules by body.

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Race within the rules

This page explains what governing bodies, regulators, standards bodies and researchers publish. It is not a substitute for your class's rule book, a track's safety rules, the race director or the makers' instructions.

A battery fire is an emergency

A smoking or burning lithium battery needs the emergency services, and a burn needs medical care. This guide gives no charging, storage, disposal or firefighting steps, and no battery, charger, sack or case is presented here as preventing a fire.

The class sets the pack

EFRA (Handbook 2026) and IFMAR (Electric Racing Batteries and Motors, March 2023) accept only lithium-based packs, LiPo or LiFe, and each sets the cell count by class. Their rules agree on most figures but are kept apart here because each applies only to its own events.

ClassEFRA 2026 (Appendix 3, A 3; Appendix 4, 1.4)IFMAR (March 2023, 3.8 and 3.15; e-buggy April 2023, 2.3)
1/121S, at most 3.8 V nominal (LiPo) or 3.3 V (LiFe); receiver batteries allowed1S only, 3.8 V (LiPo) or 3.3 V (LiFe), no larger than 93.0 x 47.0 x 18.5 mm
1/10 touring, Formula One, FWD2S, at most 7.6 V (LiPo) or 6.6 V (LiFe); no receiver batteries2S only, 7.6 V (LiPo) or 6.6 V (LiFe), for touring and F1 (3.8 does not name FWD); no extra receiver pack in touring
1/10 off-road2S, as above; no receiver batteries2S only; an extra receiver or servo pack allowed
1/8 electric off-roadAppendix 4 sets 4S case sizes and 15.2 V; EFRA's own 1/8 class rule was not read4S, at most 15.2 V, as one 4S, two 2S or four 1S packs of the same brand and part number

The receiver-pack rows are a real disagreement between the two bodies for 1/10 off-road. GT12 under EFRA uses only packs from its "1S Stick Lithium Battery Homologation List" (Appendix 3, C 5). The battery rule checker compares a pack's cells, voltages and case size with these limits; it does not check approved lists.

What the rules ask of the pack itself

  • Hard case. Both bodies require a hard protective case of ABS or similar, completely enclosing the cells and factory sealed so that opening it destroys it (EFRA Appendix 4, 1.1; IFMAR 2.1 to 2.3).
  • Label. The original label must show the part number, nominal voltage, chemistry, energy in Wh and C rating (EFRA 1.6; IFMAR 2.6 to 2.8).
  • UN 38.3. Both require safety-test certification to the UN Manual of Tests and Criteria, Part III, subsection 38.3, tests T1 to T8, before a pack can be approved (EFRA 3.3(a); IFMAR section 1).
  • Approved lists. Only batteries shown on EFRA's website are legal at its events (Appendix 4, 2); IFMAR publishes an Approved Product List for each year's Worlds (3.1). ROAR's update of 18 October 2024 (rule 11.2.1.14) makes makers responsible for knowing when their approvals expire.
  • Charged voltage at events. EFRA (2.7) and IFMAR (2.5 and 3.12 to 3.14) cap LiPo at 4.20 V per cell, 8.40 V for 2S. ROAR's battery rules as reprinted by LiveRC in 2011 allowed 4.25 V per cell; ROAR's current figure was not confirmed.
  • No heating or cooling. Both ban added heating or cooling of packs, freeze sprays included (EFRA 2.5; IFMAR 3.12 to 3.14).

Chargers and LiPo sacks: rules, not instructions

Both bodies set event rules on chargers, named here only. EFRA (Appendix 4, 2.2, 2.3 and 2.9) and IFMAR (3.9 and 3.10) require LiPo/LiFe-capable chargers using the constant-current, constant-voltage profile, and IFMAR also bans converted PC power supplies feeding chargers, with disqualification for breaches. EFRA's same rules also cap charge and discharge currents at its events. At electric European Championships EFRA requires a 220-volt supply near the pits with one outlet for every four drivers (Appendix 3, A 1.1.9), and a fire extinguisher must always be in the pits (A 9.1.4).

EFRA requires drive batteries to be in a "LiPo sack" whenever they are charged or discharged, except in a race or on organiser resistors (Appendix 3, A 3.4; Appendix 4, 2.4); IFMAR's March 2023 rule (3.11) speaks only of charging, and its e-buggy book of charging or discharging. EFRA's 2024 General Rules (5.3.12) word it more widely, requiring all racing batteries and car and radio equipment to be charged in a sack; the 2026 General Rules were not read. Both bodies define the sack as built to contain a LiPo or LiFe fire. That is the rules' definition, not evidence that a sack prevents or contains a fire, so this guide has no pick for sacks.

Travelling with packs

IATA's passenger guidance of 31 March 2026 sets lithium-ion limits by Watt-hour rating: spares are carry-on only and must be protected against short circuit; up to 100 Wh needs no operator approval; over 100 Wh up to 160 Wh needs approval; over 160 Wh goes only as cargo. IATA says it is guidance, not a source of regulatory compliance, and it never names lithium polymer, so this site does not say which category a racing pack falls into. EFRA says it approves only batteries within passenger airlines' energy limits (Appendix 4, 1.7). FAA and PHMSA pages could not be read. Full detail: travelling with batteries.

What the hazard rests on

No study of RC car battery fires was found. A 2023 UL fact sheet hosted by the New Jersey Division of Fire Safety says lithium-ion batteries can overheat, catch fire and explode, most often when damaged, abused electrically (overcharging or completely draining are its examples), exposed to heat or cold, or shorted internally, and advises products listed or certified by a nationally recognised testing laboratory. OSHA describes thermal runaway as a chain reaction from cell to cell. The CPSC's consumer alert 08-189 (12 February 2008) concerns RC helicopters and planes, not cars. More on battery fire risk.

Recalls: in 13-227 (25 June 2013) the CPSC recalled a 7.4 V LiPo battery sold for micro RC vehicles because its leads were wired to the wrong terminals, a fire hazard; in 04-160 (15 June 2004) a charger sold for remote-control race car batteries that could make packs overheat and explode. Two later CPSC charger recalls, 25-066 (12 December 2024) and 26-379 (2 April 2026), do not say the chargers are for RC batteries, so this site does not call them RC chargers. See recalls.

Our picks by category

PICK 1

LiPo batteries

Lithium drive packs. The class sets the cells: 1S for 1/12 and 2S for 1/10 under both EFRA (2026) and IFMAR (March 2023), 4S for IFMAR's 1/8 e-buggy. Each body races only packs from its own approved list, in a factory-sealed hard case with a UN 38.3 certificate behind the approval. For flying, IATA's limits turn on the Wh rating on the label.

Best for: Electric racers matching a pack to their class's cell, voltage and hard-case rule

Check current price →
PICK 2

Battery chargers

Chargers for RC batteries, named as a category only, with no charging steps. EFRA and IFMAR require LiPo/LiFe-capable chargers using the constant-current, constant-voltage profile at their events, and IFMAR bans converted PC power supplies. UL's fact sheet advises products certified by a nationally recognised testing laboratory; check recalls before buying.

Best for: Anyone running lithium packs who needs a charger

Check current price →

Sources

  1. EFRA Handbook 2026, Appendix 4, lithium batteries and brushless motors
  2. EFRA Handbook 2026, Appendix 3, Electric Cars (v4, June 2026)
  3. EFRA Handbook 2024, General Rules
  4. IFMAR, Electric Racing Batteries and Motors, version March 2023
  5. IFMAR, 1/8th E-buggy Off-Road Racing and Technical Rules (April 2023)
  6. LiveRC, reprint of ROAR battery rules (26 May 2011)
  7. ROAR, rule book update (18 October 2024)
  8. IATA, Passengers Travelling with Lithium Batteries (31 March 2026)
  9. UL lithium-ion battery fact sheet (2023), hosted by the New Jersey Division of Fire Safety
  10. OSHA, Lithium-ion Battery Safety: hazards
  11. US CPSC, consumer alert 08-189 on remote-controlled helicopters and airplanes (12 February 2008)
  12. CPSC, recall 13-227, batteries (25 June 2013)
  13. CPSC, recall 04-160, battery chargers for radio control (15 June 2004)
  14. CPSC, recall 25-066, battery chargers (12 December 2024)
  15. CPSC, recall 26-379, battery chargers (2 April 2026)

Keep reading

Battery rules by body

EFRA's 2026 Appendix 4 and IFMAR's March 2023 battery rules in parallel columns, IFMAR's 4S e-buggy and GTE rules, ROAR's 2011 text, the LiPo-sack rules as defined, and four disagreements: receiver packs, charged voltage, when a sack is required, and EFRA's own two texts.

Travelling with batteries

IATA's passenger guidance of 31 March 2026: Watt-hour bands, spares carry-on only, 20 spares per person, UN 38.3 and short-circuit protection; that it never names lithium polymer; how EFRA links its approvals to airline limits; and the unconfirmed US position.

Battery fire risk

What the CPSC, OSHA, a UL fact sheet, US transport regulators and two UK fire services say about lithium battery fires, and why no RC-car fire count was found.

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