An introduction to the system types, tools required and safety
What types of high voltage vehicles are there?
- Hybrid vehicle. This is the most common high voltage vehicle most garages will encounter. It uses a conventional internal combustion engine for propulsion and this is assisted as and when required by a high voltage motor(s). Although they are linked in series or sometimes in parallel, they are two separate sources of propulsion. The electric motors also recover energy during braking and recharge the high voltage battery.
- A plug-in hybrid vehicle operates on the same principle as a hybrid vehicle but has a much larger storage capacity in the high voltage battery and can be charged from an external power source.
- A full electric vehicle has only electric motors for propulsion and has a much larger battery than a hybrid or plug-in hybrid vehicle. These batteries can weigh over 300kg. External charging is required for the high voltage battery but energy recovery via the motors is the same as on a hybrid.
- A range extended vehicle functions the same as a fully electric vehicle but uses a small internal combustion engine to charge the high voltage battery if required. This engine cannot be used for vehicle propulsion. It overcomes owners “range anxiety.”
- Hydrogen fuel cell vehicles are beginning to appear, we can leave these for now, they are fully electric but on a whole new level!
How high is the voltage?
Using our test vehicle as an example, the Toyota Prius uses a Nickel Metal Hydride Battery, pictured right, it has 28 cells each of 7.2 volts. These are linked in series to produce a total of 201.6 volts DC. It weighs 53kg. The output has a 125 amp fuse protection which is housed within the battery isolation switch. Newer vehicles use a Lithium Iron battery with a higher voltage.
This DC voltage is converted into 500 volts AC three-phase to power the two motor generator units, and to power the air conditioning compressor. Anything over 60 volts DC and 30 volts rms AC presents a danger to health. If a person comes into direct contact with the high voltage present in a hybrid or electric vehicle, the result can be burns, unconsciousness, respiratory failure, cardiac arrest and electrolytic decomposition. (boiling body fluids and tissues).
Note: All high voltage vehicles also have a conventional 12 volt battery, this is just used to power up the high voltage system and is normally quite a small battery.