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.
How do I know where high voltage is present?
Any high voltage cable will be coloured orange, even people with colour blindness can normally see orange. The earth return also runs through these cables. Any component which contains high voltage will have a warning label on it.
Note: Some manufacturers use low voltage hybrid systems. These operate at 48 volts DC and have blue coloured cables. These systems are known as mild hybrids.
Frequently Asked Questions
Are these vehicles safe to work on?
• The answer to this surprisingly is yes! Let us examine danger versus risk.
What is the danger?
• Enough high voltage to cause us harm or death.
What is the risk?
• Coming into contact with the high voltage.
Can we remove/reduce the risk?
• Yes! The high voltage battery can be isolated.
Do I need to be trained or qualified?
• Yes, training courses are available from a variety of sources including the IMI.
What have we learnt?
Well, quite a lot really, we know that;
- There are 4 types of high voltage vehicle.
- How to identify a high voltage cable and/or a component containing high voltage.
- The voltage present in a high voltage vehicle, and that there is enough high voltage present in these vehicle systems to cause us physical harm or death.
- That only suitably trained/qualified people should work on these vehicles. (There is no legislation in place to enforce this.)
What equipment is required?
- A suitable exclusion area to keep untrained people away from the vehicle being worked on and warning signs to warn of high voltage. The Sealey HP55K1COMBO exclusion zone kit has 25M of chain, 6 posts, warning signs for the vehicle and keys and a warning sign for the working area.
- Grade 0 (1000 volt) high voltage gloves such as the Sealey HVG1000VL, these do not have a shelf life but must be stored correctly, kept clean and be air tested before each use. Any glove with damage or punctures present must not be used. The Sealey GT117 glove tester is designed to test this type of glove.
- An electricians insulating mat. The Sealey HVM17K02 insulating floor mat provides 17,000 volts of insulating protection. This must be used in conjunction with the gloves.
- High Voltage Rescue Pole. In case of an accident, a means of recovering the casualty is required. The Sealey HRP45 provides 45,000 volts of insulation protection.
- Category III volt meter such as the Sealey TA302. This type of meter is built in a specific standard to ensure safe working on the voltage and high current found in high voltage vehicles. Non compliant volt meters carry a risk of internal current jumping and shorting, there is also a risk of current jump from the leads to the user.
- Sealey provides a wide range of VDE tools. These are insulated tools and have to be tested, passed and certified to a set standard. These are easily identifiable by their distinct insulation colouring.
- Most people when working on a high voltage system will not be working on a live circuit. However, it is good practice to use these tools when carrying out this type of work.
- If a non-insulated tool is mistakenly dropped or comes into contact with a live high voltage area, the arc flash created can cause severe burns.
How old is this technology?
Hybrid technology is often thought of as a new idea. The first hybrid car was designed in 1898 and was exhibited at the Paris Exposition of 1900. It was the Lohner-Porsche Elektromobil, It was designed by a 23-year-old engineer, unknown at the time, named Ferdinand Porsche. Exposition records show that Porsche’s vehicle could travel 38 miles solely on electricity.
Porsche integrated battery-powered electric motors directly into the front-wheel hubs, producing one of the first front-wheel-drive cars. He later added an internal combustion petrol engine to drive a generator, which charged the batteries. The Lohner-Porsche vehicle could reach a maximum speed of only about 35 miles an hour, but the hybrid was born.
As concerns about vehicle emissions began to be noted, interest in electric vehicles began to be looked into again. C. Russell Feldman, a founder of Motorola, explored the market possibilities for electric cars in 1962. Working with Victor Wouk, an electrical engineer and entrepreneur. Victor Wouk drove Mr Feldman’s test electric vehicles and reported that the batteries did not have the energy required to produce enough speed or range.
Dr Wouk combined the low-emission benefits of an electric car with the power of a petrol engine to produce a hybrid vehicle. Using a Buick Skylark a very crude hybrid car was built using a Rotary engine an electric motor and eight lead-acid batteries. The project was eventually abandoned due to a lack of funding.
In 1994, Akihiro Wada, executive vice president of Toyota, posed a challenge before a special team of company engineers. Build a car with double the fuel efficiency of conventional vehicles.
Three years later, Toyota introduced the Prius in Japan as the world’s first mass-produced petrol electric hybrid car. All major car manufacturers now offer a hybrid vehicle as part of their range.