Electric Vehicle Conversion/High power electrical
Be aware the presence of hazardous supplies and situations that should be approached with correct precautions and procedures to keep away from damaging, injurious, and even deadly penalties.
No a part of the first traction pack ought to be grounded (electrically linked to the chassis). Ought to any portion change into grounded it is a single fault and whereas creating a possible hazard is just not in itself damaging. By so “floating” the traction pack a single transient bridging occasion between any portion of the pack and the physique or body won’t create a hazard of fireside or spark (however can create shock hazards at different places). Periodic security testing ought to be carried out be certain that this isolation is maintained. That is simply performed by measuring the voltage to the automobile chassis from no less than two completely different potential factors of the pack. This measurement ought to be zero.
Isolation and transformerless chargers
Light-weight chargers for charging battery banks beneath the road voltage should not remoted from the AC supply since they don’t have any transformers – they apply AC impartial to at least one aspect of the pack by way of a bridge rectifier and AC floor to the chassis. Any conduction between the pack and the chassis will create a possible shock hazard that’s detected by the bottom fault detector on the AC aspect of the charger, which then triggers and stops the cost. It isn’t potential to correctly use such a charger until the pack is correctly remoted. Since an growing older DC motor can have small present leakage because of the accumulation of conductive mud from brush put on it’s best if the pack is remoted from the controller and motor throughout charging – this is likely one of the causes for utilizing each twin contactors and switchable pre-charge resistors as proven within the diagram at left. If such a properly remoted pack causes a floor fault when a cost is tried the possible trigger is a few battery leakage or spilling of electrolyte inflicting a conductive path to the chassies, which (if the case is just not perforated) could also be corrected by cleansing the battery with an answer of sodium bicarbonate (for acid sort batteries), or weak acetic acid (for base sort batteries), adopted by a water rinse and drying.
Contactors (strong relays) make the connection between the battery pack and the controller and motor. They’re powered by a 12 volt DC supply supplied by a “run” circuit and supply disconnection when the automobile is just not in use. These contactors are usually opened by a spring and are drawn closed by a solenoid operated by the automobile’s twelve volt service battery by way of wiring known as the run circuit.
Through the use of electrically managed contactors it turns into potential to disconnect instantly upon detection of a collision (this job is carried out by routing the ignition or run circuit by way of an inertial swap (one is proven beneath)). It’s extremely fascinating to put in a disconnect at both sides of the pack, forming a redundant circuit. The disconnection of each side permits the battery pack to be utterly remoted from the controller and motor throughout charging, decreasing the probabililty of floor faulting by way of the motor or controller on the charger AC line. (Brushed DC motors produce a effective conductive mud from brush put on which may result in minor floor fault situations in damp situations adequate to set off an AC GFCI gadget.) Addtional isolation could also be required the place a contactor pre-charge is in any other case at all times on as proven within the preceeding part regarding charger management.
By eradicating the twelve volt supply the contactors will open. This shouldn’t be performed whereas the automobile is working underneath energy besides in emergency as it will trigger arcing and put on on the contactor. The contactor(s) are actuated by the “run” circuit, activated by the automobile’s ignition and begin keyswitch positions. One of many contactors shall be bypassed by a controller precharge resistor. This resistor will cost the enter capacitors of the controller to forestall a dangerous inrush present that may weld the contactor closed and so making it ineffective as a security and turn-off gadget. For isolation of the motor throughout charging these resistors ought to be in a circuit that’s open throughout charging. That is merely carried out by placing the resistors on the usually closed contacts of a double pole, double throw (DPDT) relay with an AC coil powered by the charger AC mains voltage. The usually open contacts of this relay could also be used to use the charger output to the battery aspect of the every contactor, though it’s extra frequent to completely join the charger to the battery pack by way of acceptable fuses.
Not less than one of many contactors ought to be situated near the battery pack with a purpose to present efficient safety to the cable runs from the pack to the motor and controller ought to a collision be detected.
If a contactor is above or throughout the battery compartment
then the contactor should be a sealed, explosion proof sort.
Open body contactors can create a spark
which may ignite hydrogen fuel.
Traction pack fuse or circuit breaker
The pack should even be fused near the pack. The popular location (and required for racing purposes) is within the electrical middle of the pack. This can be performed additionally by a top quality circuit breaker, which could be advantageous as it could possibly additionally carry out guide switching operations to simply isolate the pack for automobile upkeep, decreasing the necessity for a guide disconnect.
Traction pack swap
A bodily swap ought to be supplied that forestalls present circulation by way of the system. For racing purposes that is required by NEDRA rules to be accessible from exterior of the automobile.
The conversion ought to have some technique of manually disconnecting the pack on no less than one aspect to make the system secure for upkeep, even when a circuit breaker is included. This can be performed by offering a wing nut to connect one of many battery cables, though a circuit breaker, excessive present connector or swap is best, since an insufficiently tight battery connection may cause the lead publish of the battery to overheat and soften. Alternatively, the battery connections could also be opened utilizing a wrench. Any instruments used across the batteries ought to be properly insulated and brief sufficient to cut back the potential of creating an unintentional brief circuit
The controller shall be seen by the battery and contactor as a big capacitor. The inrush present to cost this capacitor may cause an arc when the contactor is closed and this will in flip trigger contactor level pitting and put on. Within the worst case this inrush present may cause the contactor to weld within the shut place. If mixed with some failure of the controller, dashpot, or accelerator pedal mechanics this might trigger an uncontrollable acceleration of the automobile. The welding of the contacts is prevented by bypassing the contactor with a resistor which permits the controller capacitance to be charged to shut to the pack voltage previous to contactor closure. Because the controller seems as a excessive sequence resistance in parallel with a excessive capacitance (and so not drawing a lot present after the precharge), many installations completely bypass the contactor(s) with this resistor. Be aware that this isn’t as secure as it’d in any other case be since pack voltage is current on the controller and throughout the passenger cab even when the contactors are open, and the controller capacitors can present vital present for a second.
Alternatively, the pre-charge could also be utilized with the ignition voltage when the hot button is turned to the Run place. By connecting the pack voltage meter throughout the controller then this pre-charge could also be noticed and the complete cost famous on the voltmeter previous to participating the beginning swap. This requires operator consideration, nevertheless and so is just not one of the best answer.
A greater configuration is to make the pre-charge present from this resistor circulation by way of a startup sequence relay. It is a delicate relay that opens when the pre-charge present drops to some low worth. Together with a secondary contactor on the pack this ensures that the motor compartment doesn’t current uncovered any pack voltage past the contactors when the system is within the “off” state. To forestall arcing because of hasty operation (rapidly turning the important thing from “off” to “begin”) a further sense circuit should be added to make sure that the first contactor is just not closed till the pre-charge is full. If a secondary contactor is used then it doesn’t have to be bypassed for pre-charge (because it can not carry present till the first contactor is closed) however it should be closed instantly by the ignition circuit in order that the pre-charge circuit can function.
A movement delicate swap can be utilized to disable the ignition, which can then be manually reset to revive operation to the system. Within the occasion of a extreme bump, overturn, or collision it will disable a portion of the run circuit, eradicating the pull in voltage from the contactors. It will scale back the chance of a excessive present brief circuit and its penalties. The opening of the contactors may even disable different circuits utilizing pack voltage such because the cabin heater and the 12 volt converter, offering further safety. Contactors have a restricted cycle life when breaking the circuit underneath load, so this method shouldn’t be topic to triggering besides underneath extreme situations. A collision sense swap could also be examined for correct operation when off throttle, nevertheless, by dismounting and instantly manipulating the sensor. In accordance with directions supplied with this sensor the sensor ought to be mounted on a panel that’s inflexible, ideally close to a nook, with a purpose to keep away from false triggering from physique flex when the automobile is pushed over bumps. Additionally it is advisable that the inertial swap be situated within the motive force cabin in order that it isn’t essential to exit the automobile to reset it.
Charger floor fault detection and safety
This can be very essential that each the charger and the mains outlet or charging station to which it’s linked have correct floor fault safety. Correct mains charging connection to an EV requires no less than three and typically 4 wires. In North American wiring a provide of 110 volts to a charger requires three wire; a “scorching” (black wire at 110 or so volts, carrying the present), “impartial” (white wire at zero volts however carrying the provided present to finish the circuit) and “floor” (inexperienced wire, linked to the gear provided at one finish and to each impartial and a floor rod on the provide panel however appearing solely as a security). A “floor fault” is detected when the provided present (“scorching lead”) doesn’t match the returned present “impartial lead”) throughout the tolerance of a “floor fault interrupter”. Be aware that this doesn’t depend on the return of the fault present by way of the bottom (inexperienced) lead – such fault could be created by a return by way of the earth, the bottom lead being supplied to trigger a right away floor fault (or to blow a fuse or journey a circuit breaker) underneath sure fault situations, similar to a brief between the recent lead and the physique on a automobile insulated from earth by its rubber tires. Floor fault interrupters are designed to function when the distinction in present circulation is lower than that more likely to trigger a hazard to an individual, triggering at about 5 miliamperes, and are designed to function very quickly. Related issues apply to 220 volt methods. 220 volt methods present two phases, despatched by way of pink and black wires, with a balancing impartial (white). The bottom security is carried out by a inexperienced wire, forming a 4 wire system. Whereas on-board chargers usually have a floor fault detector inbuilt, this detector can not reply to “upstream” faults similar to one created by an uncovered wire within the extension wire offering the AC energy. For that reason, solely a floor fault protected outlet ought to be used. If a protracted extension wire is often carried then a floor fault protecting unit could also be added to the plug (male) finish of the wire. Additionally it is advantageous to incorporate a swap or a switchable present limiting circuit breaker at this level. That enables the connection to be made to the automobile utilizing an unpowered extension, with the facility then turned on close to the AC provide level. Transportable GFCI interrupters should be used with a grounded outlet to acquire the utmost safety.
Charging station floor fault safety
Charging stations utilizing Avcon paddles or giant or small inductive loops can have a floor fault detector inbuilt. The Avcon items detect circuit completion by use of a resistor and diode between the impartial and floor, and so it isn’t sensible to attach such a unit to a GFCI circuit as it would set off the upstream fault detector through the cost begin cycle. For that reason such charging stations are appropriate just for everlasting set up. Any non-GFCI protected wiring connecting the charging station to the AC provide panel should be in conduit or armored versatile cable.
Pack voltage subsystem fuses
Techniques that use or present pack voltage embody:
- Charger (twenty to thirty amps or extra)
- Twelve volt converter (twenty amps, kind of)
- Heater (thirty amps)
- Voltmeter (very low present)
Such methods are linked to the big most important energy wires at each constructive and unfavourable. Not like standard automotive wiring, which solely fuses the constructive aspect, security dictates that each sides be fused. That is required because the battery system is floated from floor and a fault to the chassies on one aspect can convey the other polarity to the pack voltage relative to the chassies. A subsequent (or latent) fault the subsystem may overheat the wire if not fused. The fuse ought to be positioned the place the wire dimension steps down, with particular fuses (and acceptable rankings) for every gadget and the wire supplying energy to the gadget. Since an EV will in all probability have fuses distributed bodily over the automobile the documentation ought to embody a fuse map, or subsystem element places ought to be situated on the suitable circuit diagram.
Electrical Car Conversion Index
- Applied sciences
- Battery disposition, safety, and wiring
- Auxiliary methods and management
- Chassies, suspension, and working gear
- Excessive energy electrical
- Controls, interlocks, indicators, and alarms
- Conversion of concrete automobiles