This document contains our interpretation of ASC regulations, section 8 revision C. Items highlighted in red require action to be in compliance.

8. Power

Natural solar radiation received directly by the solar collector is the only source of energy that can be used for propulsion, except for energy stored in the solar car’s battery system at the beginning of the Event or metered AC charging of MOVs. Energy recovered from the motion of the car during Track or Tour hours may also be used.

The solar vehicle does not use any source of energy for propulsion other than solar radiation received directly by the solar collector and energy stored in the car’s battery system at the beginning of the event. The vehicle uses energy recovered from the motion of the car during Track and Tour hours as allowed.

8.1 Solar Collector

8.1.A Cell Type

Only commercially available silicon based photovoltaic cells may be used.

Commercially available silicon cells purchased from Maxon Solar Technologies are exclusively used.

8.1.B Solar Collector Size Limits

The solar collector cannot exceed a maximum of 4.000 m2 for Single-Occupant class solar cars, and 5.000 m2 for Multi-Occupant class solar cars.

The solar collector of 3.9627m2 does not exceed the allowed maximum collector area of 4m2.

8.1.C Definition of Area

Solar collectors will be measured by summing the total area of each solar cell (including all exposed bus bars, junctions and internal structure) from manufacturer’s data sheets, validated through measurements.

The manufacture-claimed area of each cell is 153cm2. The sum of the 259 cells amounts to 3.9627m2.

3 8.1.D Concentrators

If the solar collector comprises of photovoltaic cells used with concentrators such as reflectors or lenses then the total aperture of the solar collector must not exceed the allowable total area for non-concentrator photovoltaic solar collectors. Teams wishing to use concentrator photovoltaic solar collectors must contact Headquarters for more information.

Concentrators are not used.

8.1.E Maximum Number of Cell Types and Sizes

Teams may use no more than six (6) types or sizes of solar cells.

Only one type and size of solar cell is used.

8.1.F Validation Documentation

At Scrutineering, teams must provide sample cells of each type and size installed on the vehicle as well as a detailed map of the vehicle array for validation per Reg. 5.2.F.

We need to prepare a sample

8.1.G Solar Collector Connection and Stands

8.1.G.1 All portions of the solar collector, physical attachment to the solar car, and all electrical connections between the solar collector and the solar car must be carried by the solar car. This includes but is not limited to stands, supports, and cables. This does not include hand tools that do not become part of the solar collector structure.

Design TBD

8.1.G.2 Stands used for pointing the solar collector while the car is stationary must be self-supporting; stands that rely on people as a means of support will not be allowed. Teams will be required to demonstrate stands at inspection. Team members may temporarily steady stands in inclement weather, but it will be obvious to officials if human support of the solar collector becomes routine.

Design TBD

8.1.H Water Spray

Ambient-temperature water from an external source may be applied to the solar collector using hand-pumped sprayers (of maximum volume of five (5) gallons) if the water is applied while the solar car is stationary and the application does not present a shock hazard.

8.1.I Solar Collector Reconfiguration

The solar collector can only be reconfigured for charging when the solar car is stationary.

The collector’s position relative to the chassis will not change while under motion.

8.1.J External Irradiance Amplification

External devices intended to increase the irradiance on the solar collector or increase the efficiency of the solar collector must not be used at any time. Ground sheets used when charging must not increase the irradiance on the solar collector.

External reflectors or other amplification devices will not be used.

8.2 Energy Storage

All solar cars are allowed to store solar-generated energy in an energy storage system composed of individual cells having a weight determined by the technology used. Adherence to weight limitations does not imply automatic battery approval. Battery approval forms must be submitted to ASC Headquarters before official approval may be issued. The Inspectors reserve the right to refuse approval of modules. Unaltered samples of individual cells (minimum of three (3)) will be furnished for verification during Scrutineering.

Prepare 3 individual cells for sampling!

8.2.A Battery Weight Limits

8.2.A.1 Single-Occupant solar cars are limited to the following amounts of commercially available battery technologies: Li-S 15.00 kg Li-Ion 20.00 kg Li-Polymer 20.00 kg LiFePo4 36.00 kg

The LG M50 weighs at most 69g, resulting in a maximum total cell weight of 19.872kg, under the 20kg limit.

8.2.A.2 Multi-Occupant class solar cars do not have a battery weight limit.

8.2.B Other Energy Storage Methods Other energy storage technologies not mentioned (such as other battery technologies or fuel cells) will need to be evaluated by Headquarters. Samples and details of proposed systems must be submitted before the date indicated in Reg. 4.3.A.2.

The energy storage method used is Li-Ion.

8.2.C Supplemental Batteries

8.2.C.1 Supplemental, replaceable batteries carried in the solar car may be used to power: Main Power Switch, driver ventilation fans (if solely used for driver ventilation), telemetry, and the horn. All other systems present on the car must be powered off the main battery.

If the Main Power Switch is closed and the main battery is supplying power to the vehicle, no other systems other than those allowed are powered off the supplemental battery. See 8.6.A for interpretation on MPS. The driver ventilation fans are used solely for driver ventilation, and not any other purpose required for the function or homologation of the vehicle such as cooling of components or motive thrust. If present, the telemetry system will consist of components only used for the logging and transmission of data, and will not contribute functionally to the vehicle. The horn is powered solely and directly off the supplemental battery.

8.2.C.2 Supplemental battery power may be used to momentarily power the battery protection system (BPS) as defined by Reg. 8.3 to verify safe battery parameters before energizing the Main Power Switch.

Before the MPS is energized, the BPS is powered with the supplemental battery. See 8.3.A for interpretation of BPS definition. Once the battery parameters have been verified to be in spec, the MPS will not energize until the driver transitions the vehicle to the “drive” state. While the vehicle awaits the command from the driver to energize the MPS, the BPS continues to remain powered off the supplemental battery since that is the only source available at that time.

8.2.C.3 During a battery fault in which the BPS has automatically opened the Main Power Switch, the supplemental battery must be used to power the BPS, BPS Strobe, and BPS Fault Driver Indication. While in such a fault state, the supplemental battery may be used to power any other systems (signal lights, rear view camera, telemetry, etc) that do not provide motive power to the vehicle.

All low voltage systems in the vehicle, including all BPS components, will be powered off the supplemental battery during a BPS fault. No low voltage system is capable of providing motive power.

8.2.D Commercial Batteries

Commercially available panel meters, cell phones, tablets, driver communication radios, and other electronic devices with their own batteries may be used if the battery is not connected to the vehicle electrical system.

8.2.E Other Storage Devices

If any other energy storage devices are used (Reg. 8.2.B), they must be shown to be storing no energy and fully discharged before the start of each Tour day.

No other energy storage devices are used, other than the momentum of the vehicle for regenerative braking as allowed.

8.3 Protection Circuitry

All batteries must have protection circuitry appropriate for the battery technology used. Proof is required at Scrutineering that the protection system is functional and meets manufacturer’s specifications. Testing procedures will be provided, and the protection system design should allow for such testing. All protection circuitry should be contained in the battery enclosures per Reg. 8.4.

The main Li-Ion battery pack has active protection, and the supplemental battery has passive protection. The circuity for both these systems are contained within the main battery enclosure. See [BPS Testing Provisions] for how the BPS will be tested during scrutineering.

8.3.A Definitions

8.3.A.1 Cell: The smallest available source of energy in the battery pack as purchased from a manufacturer. A single electrochemical cell.

8.3.A.2 Module: The smallest grouping of paralleled cells easily removable in a battery pack.

8.3.A.3 String: The smallest series of modules that make-up the battery pack required voltage.

8.3.A.4 Protection Limit: The measured level determined to be adequate to protect from an event.

8.3.A.5 Active Protection: System in which measurements are constantly monitored and where actions are taken immediately without operator intervention to open the Main Power Switch should a Battery Protection Fault occur. Any protection faults will latch such that a manual clearing process is required by the driver with the vehicle not in motion and only after faults have been verified clear by the protection system.

8.3.A.6 Passive Protection: System in which measurements are monitored by the driver and where action is driver controlled.

8.3.A.7 Battery Protection System (BPS): The system that applies Active Protection to protect battery pack.

8.3.A.8 Tap: Wiring that is bonded to an electrical connection point in a circuit for remote voltage or signal measurement

8.3.A.9 Safe State: A stable electrical shut down condition where the battery pack and all its sub components are completely isolated from all potential current paths exiting the battery enclosure.

8.3.B Types

8.3.B.1 Li-Based: All lithium based battery packs must have active protection such that over-voltage, over-temperature (for charge and discharge rating), over-current and under-voltage cause the Main Power Switch per 8.6.A to open and to electrically isolate the source or sink for the vehicle. The level of protection measurement is required down to the module level at a minimum and may be required at a cell level depending on the cell manufacturer. Fuses per Reg. 8.5 are not allowed for battery over-current protection.

8.3.B.2 Supplemental: All supplemental batteries must have at a minimum Passive Protection for under voltage where charging occurs remote to the solar vehicle unless they are primary cells. Active Protection is required if charging is within the solar vehicle. No Secondary Lithium battery types shall be used for the Supplemental Battery