All the things you need to know about electric cars, written down as succinctly as I can (which isn’t very). Note that this is UK/EU specific and excludes and proprietary stuff (e.g. Tesla-specific tech)
Units of power and battery sizes
You will see the following units of power/energy/battery capacity:
- kW (kiloWatt) – This is a measure of the flow of power. It is used to describe charging speeds (how fast energy gets into the battery) and motor/engine power.
- kWh (kiloWattHour) – This is a measure of energy capacity and is used to describe how big your battery is. 1kWh is the energy used by a 1kW motor for 1 hour.
Examples:
- If you have a car with a 100kW engine/motor and a 50kWh battery you can (in theory) run it at full power for half an hour. Or at half power for a full hour. In practice there are other factors. Check the specs!
- A 100kW car will have more power to it than an 80kW car. This usually means it accelerates and drives faster. But it may be less efficient and use up your battery faster.
- A higher power charger will fill your battery faster. e.g. a 50kW charger will fill your battery faster than a 7kW charger.
- A 7kW charger will fully charge a 35kW battery in _about_ 5 hours (likely to be more – check the specs)
How big should my battery be?
The “range” of your car is determined by the battery capacity, car efficiency, driving efficiency, and other factors like the temperature. In general I would say:
- Less than 30kWh batteries are only good for short urban driving.
- 30kwH – 50kWh batteries are better for longer range, but this is very much dependent on efficiency of the engine and driving style.
- More than 50kWh batteries are needed if you are going to make longer journeys without stopping to charge up.
Charge speeds and modes
AC vs DC charging
- AC (alternating current – a type of electricity flow) charging is slower and includes home-based charging both from 3-pin cables and home-installed charge points.
- DC charging (used in “rapid” or “super-fast” chargers) is much faster and only available at public charge points.
The difference is useful to know when you’re understanding charge ports.
Charge speeds
Common charge speeds you will see are:
- 3kW – Slow home charging and slow public chargers. Sometimes called “trickle charging”. AC charging using a 3-pin or type-2 cable.
- 7kW – Faster home charging from an installed charing point. Also slow public chargers. AC charging using a type-2 cable.
- 22kW – Medium-speed, AC public charging using a type-2 cable.
- 50kW – “fast”/”rapid” charging. Usually DC using a CCS or CHAdeMO cable (depending on your car). I believe some AC chargers can get up to this kind of speed too.
- More than 50kW (75kW, 100Kw etc, up to 350 or 400kW) – you’ll only see these at public charge points. DC charging using CCS or CHAdeMO cables.
The speeds you can charge at are dependent on your car. I’d recommend looking for a car that has at least 50kW rapid charing using CCS.
Charge ports
Charge ports/cables are fairly standard, but there are different types.
- 2/3-pin – These cables are used for AC home charging (make sure your home wiring can cope!). They usually have a 2/3-pin connector on one end and a type 2 connector to plug into the car.
- Type 2 (sometimes called “Mennekes”)- This is a round connector with 7 pins. Used for AC charging up to around 22kW.
- CCS adds extra DC connectors to a Type 2 port to allow “rapid” charging at speeds above 22kW.
- CHAdeMO – This is a Japanese standard for “rapid” charging. I only saw it on Nissan Leaf’s and it’s not available at all charging points.
You will most commonly see Type 2 ports on British/EU cars as they are mandatory. It’s recommended to have a CCS port.