From the Questionnaire - part one
Q3 2.2(1)(e) Mechanical master switch
Should a mechanical master switch be mandated to disconnect batteries and can it be in battery box if non–venting type batteries are used?
I am using Alderson connectors to disconnect my batteries into partial packs
– is this a “mechanical switch”?
Q4 2.2(3) High voltage
UNECE regulations designate high voltage as 60V DC and 25V AC. Australia requires orange cabling for any voltages over 32V. FIA set the limit at 42V and 50V depending on vehicle type. What should the figure be set at?
I would recommend setting it at the lower of the two levels 42v DC and 25v AC
Q5 2.2(5)(b) Over‐current device
Can an over‐current device be in a battery pack?
In the case of a lead acid battery that would be a bad idea as an explosive gas mix may be present, for all other chemistries an overcurrent device should be as close to the batteries as possible so inside the pack would be ok.
Q6 2.3(1) Battery restraint
What is a sensible acceleration level to apply to battery restraint in directions other than forward?
The 2.5G in the draft standard is a good number – should also apply to vertical acceleration
Q7 2.3(2) Battery compartment sealing
Should drip tubes or a catch tray be allowed as an alternative to a fully sealed battery compartment?
I don’t understand what is being fixed here?
Q8 2.3(4) Battery compartment venting
Is venting of a battery compartment required when batteries are discharging, or only when charging or during regenerative braking?
Only when being charged or during regenerative braking – only for lead acid batteries
Q9 2.4(1)(f) Ground fault detection
Should a manual ground fault detection system be mandatory?
No – with a brushed DC motor ground fault detection will be very unreliable
Q10 2.4(2) Accelerator design
Fail‐safe accelerator design – it is assumed that a single potentiometer is not sufficient and a twin potentiometer should be used.
Existing motor controllers do not have the facility to use twin potentiometers, a better system would be to use the throttle potentiometer (or hall-effect unit) in series with a micro-switch on the throttle lever then both would need to be activated to allow current to the motor.
Additionally the controller should not be able to be switched on (initial switch on) unless the throttle is at zero or the micro-switch is open
Q11 2.4(3) Transmission
Should the trans have an inhibitor to prevent motor energisation whilst in gear, for auto and manual transmissions?
I assume this means initial switch on of the controller –
This would be very difficult for a modifier to do
A switch on the accelerator as above or a switch on the brake would be much easier to do, would give equal or better protection and is similar to the starter inhibitor on the clutch on some IC vehicles.
The vehicle I am building is direct drive with no clutch – there is no way to mechanically disconnect the drive
Q12 2.6(1) High voltage warning labels
Should high voltage stickers on bumpers be mandatory?
Warning is needed “under the hood” or anywhere where the high voltage can be encountered,
Is external warning really needed?
Q13 ‐‐‐‐ Current switches
The FIA specifies the following requirement:
"In order to prevent contact melting of the general circuit breaker its [I²t] (ampere square seconds characteristics, representing heat energy dissipated on the breaker contacts during switching) must be sufficient to guarantee proper operation of the circuit breaker, even under surge current conditions, in particular those occurring
during the connection of the traction battery to the power bus."
Should we include a similar requirement?
In normal operation contactors should never have to make or break under load,
Contactors should be capable of making and breaking the currents required –however they should not be required to have a long life under these conditions. Tens of operations to failure not thousands
even under surge current conditions, in particular those occurring during the connection of the traction battery to the power bus
This would be an indication of very poor design – the power pack should be connected to the controller through a resister until the capacitors have charged to the pack voltage and only then should the main contactor pull in. (PreCharge)
Q14 ‐‐‐‐ Insulation resistance testing
Should Insulation resistance testing (from UNECE 100) be mandated?
Certifiers will need to use a specialist meter to do this (also see FIA requirements in Q15).
For the foreseeable future brushed DC motors will be the most commonly used motors, these have inherent leakage due to carbon dust
This makes mandatory testing useless
Q15 ‐‐‐‐‐ Insulation resistance testing
The FIA specifies the following requirement:
“Every part of the electrical equipment must have a minimum insulation resistance between all live components and earth.
‐ For equipment with up to 300 volt to earth, the insulation resistance must reach the following value: 250 k Ohms.
‐ For equipment with more than 300 volts to earth, the insulation resistance must reach the following value: 500 k Ohms.
The measurement of the insulation resistance must be carried out using a d.c. voltage of at least 100 volts.”
Should we include a similar requirement?
As above this is useless with brushed DC motors
Q16 ‐‐‐‐ Insulation performance
The FIA specifies the following requirement:
“All electrically live parts must be protected against accidental contact. Insulating material not having sufficient mechanical resistance, i.e. paint coating, enamel, oxides, fibre coatings (soaked or not) or insulating tapes are not accepted.”
Should we include a similar requirement?
This is seems to be sensible but on closer examination is silly there are lots of parts inside their compartments that cannot be properly insulated
It must be clear that this does not include parts that are safely inside their compartments otherwise we will have issues with battery terminals and motor terminals and all of the bits inside my controller.
If you open the hood or battery box there will be “hot” parts in there unless you have disconnected the battery pack – as you should if working there
If you open up a main circuit board on a building you will find a plastic protector plate and underneath lots of un-insulated parts
Also needs to be expanded so that I can use taped on plastic tubes for instance