On or Off-board charging
When considering whether to use on-board or off-board charger decide a few simple specification requirements.
1. What type of vehicle are you charging?
If it is a small city car which has a 10-20kWh battery then a single phase 13A domestic supply would be adequate. This is a relatively small component which more than likely will be on-board. If the battery and vehicle are larger then the option is there for either or solution.
2. What charge time is required?
If a fast or rapid charge is required then even for a 10-20kWh battery, the charger will be relatively heavy and large. It will also require higher levels of cooling. Therefore an off-board is the likely solution.
3. Is charging always done at one location?
If charging is always done at the same location then an off-board charger can be considered rather than carrying the chargers around.
4. Is there space on the vehicle?
Obviously if there is no available space on a vehicle then the charger will have to be off-board. Otherwise a smaller charger with an increased charge time may be appropriate for times when the vehicle cannot get back to base or only has access to a 13A supply.
5. What is the fleet size?
For fleets of five or more vehicles there is the opportunity to share off-board chargers between vehicles so the ratio does not have to be 1 to 1 charger to vehicle. This will save money.
Installation of chargers
This applies mainly to off-board chargers but has to be considered for on-board also. Off-board chargers can be reasonably large and heavy so position and installation of the chargers is important and has to be planned before hand.
They have to be close to the vehicle (less than 3m). They also should be positioned close to the buildings power distribution circuit to reduce the length of cable. Chargers can draw very large current (415V, 3 phase, 270A per phase) so cable and installation costs can be tens of thousands of pounds and stretch the available power resources of the facility.
Chargers have to be positioned where their controls are easily reached but protected from damage by material handling equipment and vehicles. Adequate ventilation has to be provided as larger chargers require a lot of forced air cooling. Because of this they can be noisy so they should not be located in quiet areas.
On-board charges require single or 3 phase mains power to be connected to the vehicle. Appropriate plugs and sockets must be used and installed to meet current building and IEE regulations.