Only NiCd or NiMH sub-C size rechargeable batteries rated at 1.2 volts or less may be used for the motor power in electric vehicle racing. ROAR Approved Lithium battery technology may be used as a option in any 6 cell 7.2 volt NiCd NiMH electric vehicle racing.

Dimensions: Sub C only
Diameter: Maximum 23mm, Minimum 21.5mm
Length: Maximum 43mm, Minimum 41.5mm
No further tolerances are allowed on these dimensions.
Batteries must receive ROAR approval to be legal for use in ROAR-sanctioned events. NiCd or NIMH Cells submitted for approval shall measure 43.0mm in can length which does not include the center positive button. Individual cells shall be constructed such that the total overall length resulting from the combination of charging and/or conditioning never exceeds 44.0mm. This may be verified at competition technical inspections.

Lithium Polymer Batteries (LiPoly)

Li-Poly battery packs must have a hard, protective case that surrounds the cell(s) in the racing application. A factory encased hard shell pack is mandated for race durability reasons that stem from the vulnerability of Lipo cells to physical damage. Any physical distortion, denting or puncture to the cells will cause either an immediate or long term safety risk. A hard cased pack reduces this risk significantly by protecting the cells from crash damage, battery ejection, and general wear and tear at the track. ROAR defines the "hard case" as a case made of ABS or similar type material. The case shall consist of two (2) halves with each half being constructed from a single mold that is not easily pliable and retains it shape without any exterior or interior support. Both the top and bottom sections of the case must be secured together by glue, double-sided tape or heat seal with a label across the seam stating "ROAR Approved" in such a manner that separation of the case to remove or replace the cells will destroy the case and/or label and render it unusable in competition. The case must be installed by the manufacturer or Value added manufacturer no end User installed cases are acceptable. The case will protect the cells from damage on all sides and will completely cover all cells having only openings for wire connections. Any modification to the factory approved hard case will make the pack ineligible for participation in ROAR events.

The maximum case size shall be as follows:

Length: 139mm +0mm/-3mm
Width: 47mm +0mm/-2mm
Height: 25.1mm +0mm/-3.0mm

The battery pack shall have leads extending from the case for the positive and negative electrical connections using wire of adequate size to handle discharge rates acceptable to racing applications. Alternatively, the case shall have external connection points for these wires clearly marked positive and negative so the user can apply the lead wires. Markings on the case are required stating the rated voltage and capacity of the battery. The Value Added Manufacturers name and/or logo shall be easily readable on the case. Individual cells used in the construction of the battery shall be rated at 3.7 VDC and the pack shall be 2 cells in series.
The cells of the battery pack shall experience no loss of mass, no leakage, no venting, no rapid disassembly, and no rise in temperature. The case shall not splinter or shatter in a manner that would create shrapnel and potentially puncture the cell inside.
General information about Li-Poly batteries.

Lithium Polymer packs must be charged with chargers capable of the industry standard CC/CV (Constant Current/Constant Voltage) charge profile. Li-Poly batteries may be charged to a maximum of 8.40V +/-0.04V. Overcharging is a serious safety hazard and will not be tolerated. A Lipo battery pack is damaged when any of the following rules are broken. The damage is cumulative and cannot be reversed. These rules provide the safest operation and longest pack life. Going outside these rules may result in a destructive pack failure.
Do not over discharge Lithium Polymer battery packs and use a Proper ESC cutoff voltage. Some newer speed controls give you the option to set a cutoff voltage, and some do not. The cutoff voltage setting is working properly when the ESC does not allow the motor to spin anymore when the pack voltage reaches this set cutoff. A Lithium Polymer battery is damaged when it goes below a set voltage whether under load or not. The lower the voltage and the longer it stays low, the more damage is occurring to the cells. If your ESC doesn't have a setting for cutoff voltage, we strongly suggest not using any Lipo pack with it unless you have a secondary device to cut off the motor at the correct voltage. By the time the pack “feels soft” at the end of the run or you notice any decrease in power, the pack has already been damaged. Consult your Lipo pack manufacturer for the proper low voltage cutoff since this value varies based on manufacturer.
The maximum safe temperature of a Lithium Polymer pack is 140degF. Generally the pack temp will INCREASE for about 5-10mins after the run is over, so measure the temperature of the pack immediately after the run and then again about 10 minutes later. The faster the car is geared, the more amps the motor is drawing and the battery is delivering. The less capable of outputting high current (amps) the pack is, the more it will heat up with the same load (think IB4200's vs. NiCad 2400's on a mod motor) Exceeding 140degF pack temperature causes damage, and the pack is also less efficient at near critical temperatures.
Only charge Lithium Polymer packs with a charger that uses the industry standard CC/CV charging algorithm for Lithium based batteries. There are two settings you will need to either set or verify on your charger each and every time before you begin charging a pack. The first is the pack voltage or cell count (each charger uses different nomenclature). If your charger is asking for the voltage of the pack, the choices are 3.7v (one cell), 7.4v (two cell), and 11.1v and beyond (3+cells). ROAR legal Lithium packs are all two cells, or 7.4v packs so set your charger accordingly. Some chargers ask for the cell count of the pack (one cell, two cells, and etc.) so you would set it for a two cell pack. The next setting is the charging rate. Lithium Polymer battery packs not only show no performance benefit from charging at higher than recommended rates, but they can be damaged by charging rates that are too high. The standard charging rate is “1C” which means the actual capacity of the pack in Milliamp hours. We charge in Amps not Milliamps, so divide the Milliamp Hours (Mah) of your pack by 1,000 to get your proper charging rate. For a 4800mah pack, 4800mah divided by 1,000 = 4.8 Amp charge rate. For a 3200Mah pack = 3.2 Amps, and a 5000Mah pack = 5.0 Amps. Unless specifically recommended by the manufacturer with no loss of cycle life, a maximum of 1C charge rate should always be used.

Body Rules:

Length: (B) Maximum 460 mm
Width: With body Maximum 195mm
Without body Maximum 190 mm
Height: (with 20mm blocks under chassis)
Maximum 190 mm
Minimum 130 mm
Wheelbase: Maximum 270 mm
Minimum 250 mm

Weight Minimum – Foam 1418 g
Minimum – Rubber 1525 g

Wheels Diameter :

Maximum – Foam 53 mm
Maximum – Rubber 50 mm
Minimum 47 mm

Width

Maximum - Foam 28 mm
Maximum - Rubber 26 mm
Minimum 24 mm

Tires

Diameter Maximum – all types 67 mm
Minimum – Rubber only 63 mm
Width Maximum 28 mm
Minimum 24 mm

Rear Wing

Chord Maximum 40 mm
Width Maximum 190 mm
Side dam length Maximum 40 mm
Side dam height Maximum 20 mm
Vehicles must comply with both specifications during a single inspection.
Tire type:

• Paved Surfaces: Rubber only
• Capped tires are not allowed on any surface.

Battery Cells: Six cell maximum or 2 cell 7.4 lithium battery

Transmission: Single speed only

Front and Rear suspension: Independent.

Drive: 4WD only.

Body rules:

• Bodies must resemble 2 or 4 door cars that have raced in a Touring Car series.
• Wheel arch cut-outs: Maximum 9.5 mm over tire diameter
• The rear of the body may not be cut higher than 55mm above the measuring surface with the chassis resting on 20mm blocks.
• No windows may be cut out.

Wing rules:

• Only one wing is allowed, fixed to the same place as the wing on the full-size vehicle.
• The wing must be fastened to the rear deck of the body, not directly to any part of the chassis of the vehicle.
• The rear edge of the wing or side dams may not extend beyond the rear of the body more than 10 mm.
• No part of the wing may extend above the roofline of the body.