IC4.4.1 All batteries, i.e. on-board power supplies, must be attached securely to the frame.
IC4.4.4 Battery packs based on Lithium Chemistry:
a. Must have over current protection that trips at or below the maximum specified discharge current of the cells.
b. Must have a rigid, sturdy and fire retardant casing.
c. Must be separated from the driver by a firewall as specified in T4.5
EV3.1.1 All types of accumulators except molten salt and thermal batteries are allowed. E.g.: Batteries, Supercapacitors, etc. Fuel cells are prohibited.
EV3.2.1 All cells or supercapacitors which store the tractive system energy will be built into accumulator segments and must be enclosed in (an) accumulator container(s).
EV3.2.2 If spare accumulators are to be used then they all have to be of the same size, weight and type as those that are replaced. Spare accumulator packs have to be presented at Electrical Tech Inspection.
EV3.2.3 If the accumulator container(s) is not easily accessible during Electrical Tech Inspection, detailed pictures of the internals taken during assembly have to be provided. However, at the end of the event the tech inspectors reserve the right to check any accumulators to ensure that the rules are adhered to.
EV3.2.4 Each accumulator container must be removable from the car while still remaining rules compliant.
EV3.3.2 Every accumulator container must contain at least one fuse and at least two accumulator isolation relays, see EV3.5 and EV6.1.
EV3.3.3 Maintenance plugs, additional contactors or similar measures have to be taken to allow electrical separation of the internal cell segments such that the separated cell segments contain a maximum static voltage of less than 120VDC and a maximum energy of 6MJ. The separation must affect both poles of the segment.
This separation method must be used whenever the accumulator containers are opened for maintenance and whenever accumulator segments are removed from the container.
It must not be physically possible to connect the Maintenance Plugs in any way other than the design intent configuration.
EV3.3.5 The Accumulator Isolation Relays (AIRs) and the main fuse must be separated with an electrically insulated and fireproof material to UL94-V0 from the rest of the accumulator. Air is not considered to be a suitable insulation material in this case.
EV3.3.7 Contacting / interconnecting the single cells by soldering in the high current path is prohibited. Soldering wires to cells for the voltage monitoring input of the AMS is allowed, since these wires are not part of the high current path.
EV3.4.1 All accumulator containers must lie within the Primary Structure of the Frame (see T3.3).
EV3.4.3 The container material must be fire resistant according to UL94-V0, FAR25 or equivalent.
EV3.4.6 Accumulator containers must be constructed of sheet/plate steel or aluminum in the following configuration:
a. The floor or bottom of the accumulator container must be constructed of steel 1.25mm (0.049 inch) thick or aluminum 3.2mm (0.125 inch) thick.
b. The external vertical walls must be constructed of steel 0.9mm (0.035 inch) thick or aluminum 2.3mm (0.09 inch) thick.
c. Internal vertical walls separating cells and/or segments must be a minimum of 75 percent of the height of the external vertical walls and must be constructed of steel 0.9mm (0.035 inch) thick or aluminum 2.3mm (0.090 inch) thick.
d. Covers and lids must be constructed of steel 0.9mm (0.035 inch) thick or aluminum 2.3mm (0.09 inch) thick.
e. The floor and walls of the accumulator container must be joined by welds and/or fasteners. Any fasteners must be 6 mm Metric Grade 8.8 (1/4 inch SAE Grade 5) fasteners, or stronger.
f. Internal vertical walls divide the accumulator container into “sections”. A maximum of 12kg (26.5 lbs.) is allowed in any section of the accumulator container.
EV3.4.10 The accumulator segments contained within the accumulator must be separated by an electrically insulating and be fire resistant barrier (according to UL94-V0, FAR25 or equivalent) and must subdivide the accumulator into 6MJ segments if this is not already met by the separation due to the 120VDC voltage limit.
The contained energy of a stack is calculated by multiplying the maximum stack voltage with the nominal capacity of the used cell(s). Documentation of segment separation must be provided in the ESF.
EV3.4.11 Holes, both internal and external, in the container are only allowed for the wiring-harness, ventilation, cooling or fasteners. External holes must be sealed according to EV4.5.
EV3.4.12 The container must be completely closed at all times, when mounted to the car and also when dismounted from the car without the need to install extra protective covers. Openings for ventilation should be of a reasonable size, e.g. completely open side pods containing accumulators are not allowed.
EV3.5.1 In every accumulator container at least two isolation relays must be installed.
EV3.5.2 The accumulator isolation relays must open both (!) poles of the accumulator.
If these relays are open, no HV may be present outside of the accumulator container.
EV3.5.3 The isolation relays must be of a “normally open” type.
EV3.5.4 The fuse protecting the accumulator tractive system circuit must have a rating lower than the maximum switch off current of the isolation relays.
EV3.5.5 The accumulator isolation relays must not contain mercury.
EV3.6.1 Each accumulator must be monitored by an accumulator management system whenever the tractive system is active or the accumulator is connected to a charger. For battery systems this is generally referred to as a battery management system (BMS) however alternative electrical energy storage systems are allowed and therefore AMS will be the terminology used in this document.
EV3.6.2 The AMS must continuously measure the cell voltage of every cell, in order to keep the cells inside the allowed minimum and maximum cell voltage levels stated in the cell data sheet. If single cells are directly connected in parallel, only one voltage measurement is needed.
EV3.6.3 The AMS must continuously measure the temperatures of critical points of the accumulator to keep the cells below the allowed maximum cell temperature limit stated in the cell data sheet or below 60°C, whichever is lower. Cell temperature must be measured at the negative terminal of the respective cell and the sensor used must be in direct contact with either the negative terminal or its busbar. If the sensor is on the busbar, it must be less than 10mm away from the cell terminal.
EV3.6.4 For centralized AMS systems (two or more cells per AMS board), all voltage sense wires to the AMS must be protected by ‘fusible link wires’ or fuses so that any the sense wiring cannot exceed its current carrying capacity in the event of a short circuit. The fusing must occur in the conductor, wire or pcb trace which is directly connected to the cell tab.
Any distributed AMS system (one cell measurement per board) where the sense wire connections at the board are <25mm does not need additional fusing if the board is protected from short circuit and the connection to the AMS is also protected. If these conditions are not met, then the positive cell
terminal must be protected with a fusible link wire.
EV3.6.6 For lithium based cells the temperature of at least 30% of the cells must be monitored by the AMS. The monitored cells have to be equally distributed within the accumulator container(s). It is acceptable to monitor multiple cells with one sensor, if EV3.6.3 is met for all cells sensed by the sensor.
EV4.5.1 All parts, especially live wires, contacts, etc. of the tractive system must be isolated by nonconductive material or covers to be protected from being touched. In order to achieve this, it must not be possible to touch any tractive system connections with a 100 mm long, 6 mm diameter (4 x . inch) insulated test probe when the tractive system enclosures are in place.
EV4.8.1 All accumulator containers must be wired to a single point. It does not matter if they are wired in series or parallel, but all the power supplying the tractive system must flow through this single point and must pass the energy meter position, see EV4.9.
EV4.9.1 In the tractive system supply wires, see EV4.8, a calibrated energy meter must be inserted at the competition. The energy meter is used to
EV4.9.3 The energy meter must be in an easily accessible location so that the recorded data can be quickly downloaded by the officials after the Endurance Event to calculate the efficiency score.
EV4.9.4 The energy is calculated as the time integrated value of the measured voltage multiplied by the measured current logged by the Energy Meter.
EV6.1.1 All electrical systems (both low and high voltage) must have appropriate overcurrent protection.
The continuous current rating of the overcurrent protection must not be greater than the continuous current rating of any electrical component, for example wire, busbar, cell or other conductor that it protects.
Note: Fuses are the most common form of overcurrent protection.
EV6.1.2 All overcurrent protection devices must be rated for the highest voltage in the systems they protect. Overcurrent protection devices used for DC must be rated for DC, and must carry a DC rating equal to or greater than the system voltage.
EV8.4.1 In order to accommodate charging, a hand cart to transport the accumulators must be presented at Electrical Tech Inspection.
EV8.4.2 The hand cart must have a brake such that it can only be released using a dead man's switch, i.e. the brake is always on except when someone releases it by pushing a handle for example.
EV8.4.3 The brake must be capable to stop the fully loaded accumulator container hand cart.
EV8.5 Each team must present the following basic set of tools in good condition during technical inspection:
a. Insulated cable shears
b. Insulated screwdrivers
c. Multimeter with protected probe tips
d. Insulated tools, if screwed connections are used in the tractive system
e. Face Shield
f. HV insulating gloves which are within test date
g. 2 HV insulating blankets of at least 1.0mÇ each
h. Safety glasses with side shields for all team members that might work on the tractive system or accumulator
All electrical safety items must be rated for at least the maximum tractive system voltage.