Motors and batteries: from dry cells to lithium, from brushed to brushless.

This page is a dated history of the power side of electric RC racing: the batteries and the motors, and the rules that governed them. It describes what each body decided and when. It does not describe how to choose, charge, store or run any battery or motor, and nothing here says a battery or motor is approved for any event; each body's current list decides that. Where a date rests on trade press or a maker's announcement, it says so.

Batteries

Dry cells and nickel-cadmium, 1960s to 1970s

• 1966: David Palmeter's account says the Testors Mustang announced that year ran on rechargeable nickel-cadmium (NiCd) batteries. It rests on his reading of 1966 magazines and is unconfirmed beyond his site.
• 1976: Motor Sport (July 2017) says Tamiya's first RC car, the Porsche 934, first ran on ordinary dry cells lasting about ten minutes, and that Tamiya then developed rechargeable NiCd packs that became an industry standard for many years. No year is given for the packs.
• 1978: LiveRC (Aaron Waldron, 7 August 2014) says ROAR's newly recognised 1/12 electric classes were divided by cell count: 6-cell stock, 6-cell modified and 4-cell modified. This is a single trade-press source.

Wikipedia's buggy article says NiCd cells powered off-road racing from the early 1980s until nickel-metal hydride (NiMH) cells replaced them, and that 2-cell (7.4 V) lithium polymer (LiPo) packs later became the racing standard. It gives no years for either change, and the year NiMH cells entered RC car racing was not found.

The move to lithium, 2008 to 2012

The bodies adopted lithium batteries separately:

• ROAR, January 2008: Red RC (16 January 2008), reproducing the rule text, reported that ROAR had reversed an earlier ban and approved LiPo packs for sanctioned racing under rule 8.3.2. Approved 2-cell packs could run in the 6-cell sub-C NiCd and NiMH classes, subject to a certificate of compliance (from UN transport tests or ROAR's own lab tests), a hard case, identification of the cell maker and assembler, the class minimum weight, maximum case dimensions and charging limits set in the rule, and the use of a LiPo sack when charging. When ROAR first banned LiPo was not found.
• EFRA, 2009: EFRA's 2026 Handbook says it has homologated only lithium-based batteries (LiPo or LiFe) since 2009 (Appendix 4, rule 3.1).
• IFMAR, 2009: Red RC (2 August 2009) reported that EFRA proposed to IFMAR's annual general meeting at Lostallo, Switzerland, that LiPo packs be allowed at the 1:10 ISTC and 1:10 electric off-road World Championships, noting that LiPo was already used in many national championships and that unlimited modified motors raised speed concerns. The outcome was not found.
• EFRA, 2011 and 2012: EFRA's battery homologation officer wrote on 28 October 2011 that in recent years only lithium batteries had been submitted for approval and competitors no longer used NiCd or NiMH. Deleting all NiCd and NiMH rules and approval procedures was proposed for ratification at the November 2011 AGM, and EFRA's 2012 procedures covered only lithium 1S and 2S packs.

Lithium rules since

• ROAR, 2011: ROAR's battery rules as LiveRC reprinted them on 26 May 2011 rated cells at 3.7 V nominal and allowed a maximum charged voltage of 4.25 V per cell (8.50 V for a 2S pack). Whether that is still ROAR's figure was not confirmed, because ROAR's current rule book was not read.
• EFRA, 1 April 2017: cells of up to 3.8 V nominal allowed, with earlier 3.7 V approvals kept (Appendix 4, note to rule 1.4). EFRA's 1/12 rule in Appendix 3 (A 3.1) gives 1 March 2017 for that class.
• IFMAR, March 2023: IFMAR's Electric Racing Batteries and Motors document says IFMAR approves only lithium-based batteries, with a maximum charging cut-off of 4.20 V per cell and UN 38.3 test certification required for approval.
• EFRA, 2026: two battery submission dates a year, 1 December and 1 April (Appendix 4).

So the per-cell maximum is recorded two ways across bodies: 4.25 V in ROAR's 2011 text, and 4.20 V in IFMAR's 2023 document and EFRA's 2026 Handbook. These are different bodies' rules for their own events, and the ROAR figure may since have changed. Each body's current battery rules are on battery rules by body.

Motors

Brushed motors and stock and modified, 1978 to 2009

The stock and modified divisions in ROAR's 1978 1/12 classes, as LiveRC describes them, are the earliest stock and modified split found; LiveRC does not say what set the divisions apart. LiveRC's table of 1/12 world champions names the motor maker of each winner, from Yokomo in 1982 to Reedy in 2012, without saying whether each motor was brushed or brushless. Red RC (2 August 2009) reported that modified class motors then had no limit on the number of turns. The history of stock brushed motor turn limits was not found.

ROAR's first brushless approvals, 2008

RC Car Action (10 March 2008) reported that ROAR announced on 15 February 2008 the approval of Novak's SS10.5 and SS13.5 brushless motors for a class renamed Super Stock (formerly the "19T class") and the SS17.5 for Stock, and that these were the first brushless motors ROAR approved. The report repeats a maker's announcement, so the "first" is a claim. Big Squid RC (11 March 2008) reported that Novak's SS17.5 motor and GTB speed controller had recently been approved for ROAR Stock spec racing.

EFRA's brushless rules, 2011 to 2018

• 2011: spec motors introduced from this year must carry the wind number etched or engraved on the motor (Appendix 4, rule 4.17).
• 2012 and 1 March 2018: holes or slots for checking the stator required in motors whose stator cannot easily be removed, and at least two pairs from 1 March 2018 (rule 4.8).
• 2015 and 2016: the 2015 AGM agreed EFRA would homologate "05" size brushless motors; from 2016 only listed motors may be used at European Championship and Grand Prix events in 1/12, 1/10 touring and 1/10 off-road. EFRA's handbook gives the start both as May 2016 and as 1 June 2016 in different sections.
• 1 April 2015 and 1 November 2017: optional rotors covered, then limited to one per motor range.

Where the motor rules stand

EFRA's 2026 Handbook and IFMAR's March 2023 document both approve only brushless "05" motors for 1/12 and 1/10, with no turn limit in Modified. Their spec wind lists differ: EFRA lists 10.5T, 13.5T, 17.5T and 21.5T, while IFMAR lists 13.5T, 17.5T, 21.5T and 25.5T. ROAR's 18 October 2024 rule book update keeps motors with epoxy-coated stators on its approved list until 31 December 2026, with motors to a new specification legal from 1 September 2025. The year a brushless motor first won an IFMAR World Championship was not found. Current motor rules are on motors.

Nitro engines

The research for this site found no dated history of the racing bodies' nitro engine or fuel rules. The current IFMAR limits are on nitro engines and mufflers and nitro fuel rules.