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Know the Key "Number" of Electric Vehicles

Aug 30, 2023

Know the Key "Number" of Electric Vehicles

How powerful is the car running? Power unit: watt (W) and horsepower (hp)

Entering the era of electric vehicles, the most important figure to know about electric vehicles is the power output.


In the past, when we wanted to evaluate a new car, one of the most commonly used indicators was "horsepower". Horsepower determines the character of a car, whether it is a well-regulated Volkswagen, a passionate sports car, or a beast-level supercar. After horsepower is combined with car style, model, function, etc., more classifications are derived. Generally speaking, horsepower is one of the key indicators that affect vehicle performance.


When it comes to electric vehicles, the accompanying nouns that can more directly mark the power unit become "power output" and "watt (W)". Many people may feel a sense of distance when they see the power output, but in fact horsepower is also power. It is a kind of output unit, and the output unit of an electric vehicle becomes "watt (W)" of electric power. The higher the watt, the higher the power, which means the higher the horsepower.


Since both horsepower and watts are units of power, the two can actually be converted. 1 imperial horsepower is about 745.7 watts, and 1 metric horsepower is about 735.5 watts. The more commonly used form of watt is kW, read as kilowatts, which is 1 kilowatt; for example, a car with about 150 metric horsepower is converted to a power output level of about 110kW.


Let’s take the U-CAR official car Nissan Leaf as an example. The output power of its electric motor is 110kW, read as 110 kilowatts, and we know that the conversion of power into metric horsepower needs to be multiplied by about 1.36, so after multiplying 110kW by 1.36, we get about 149 horsepower ; On the contrary, when 149 horsepower is converted back to electric power, it is multiplied by 0.735, which is equal to about 110kW. In science, as long as there is conversion, there is the possibility of error. Therefore, if there is original data, the original data should prevail. If there is no, it is recommended to use the conversion method.


Ultimately, in the future, the term "horsepower" may be completely replaced by power, because current charging devices, recharging mechanisms, and even battery packs all use electrical power or electrical energy units instead of horsepower. Once electric vehicles become mainstream, daily There will be a lot of power figures in life. After getting used to it, you can even quickly calculate the charging time, cruising range, etc. at this time. If you use horsepower units at this time, not only the calculation is more troublesome, but also unintuitive.


2. The fuel tank has become a battery! Electric energy unit: kilowatt-hour (kWh)

In the field of electric vehicles, the energy source for driving the vehicle is changed from the fuel of the traditional internal combustion engine to the electric energy in the battery, and the most widely calculated unit of electric energy is kWh, pronounced as kilowatt-hour, which means that 1 kilowatt of electric power in 1 hour Work done is a unit of energy. In the vernacular, 1kWh is the "degree" often heard in daily life, 1kWh is 1 degree of electricity, 10kWh is 10 degrees of electricity, and the battery pack in an electric vehicle, regardless of its chemical composition or form, can be calculated through the formula Calculate how many kWh its capacity is.


In other words, the energy source required by the car has changed from "liters" of fuel to "kilowatt hours" of batteries. To make readers more conceptual, we take Toyota Prius as an example. The battery capacity of this hybrid vehicle is 1.6kWh, which is 1.6 kilowatt-hours of electricity. Another Toyota Prius PHEV plug-in hybrid has a battery capacity of 8.8 kWh, while the battery capacity of the pure electric Nissan Leaf is 40kWh, and the entry-level Standard Range Plus version of the Tesla Model 3 is 60kWh. The higher the kWh of the battery, the more energy it contains, and the theoretical distance for pure electric driving The longer it goes up.


3. How to calculate the energy consumption of electric vehicles? km/kWh?

Fuel vehicles and electric vehicles both consume energy to drive, while gasoline and diesel vehicles have "fuel consumption", and of course electric vehicles also have "electricity consumption". The formula is calculated to the "joule" (J) unit, which can be compared in the same unit; however, this topic does not discuss issues at this level, but how to calculate the energy consumption performance of electric vehicles.


The principle of calculating the energy consumption of electric vehicles is actually the same as that of fuel vehicles. They divide a certain energy consumption by the driving distance, or divide a certain driving distance by the energy consumption, depending on the difference in calculation habits. The most common electric vehicle Energy consumption is expressed in the following ways: km/kWh and Wh/km. The former represents how many kilometers can be traveled by 1 kilowatt-hour of electricity, which is similar to the concept of how many kilometers can be traveled by 1 liter, while the latter represents the number of watt-hours of electricity consumed per kilometer.


Taking the Jaguar I-Pace recently measured by U-CAR as an example, after the finalized road test, the average energy consumption obtained is 4.13km/kWh, which means that every 1 kWh of electric energy can travel 4.13 kilometers; Calculated per km, the converted electric energy of about 242Wh can travel 1 km.


4. It is knowledgeable to plan charging, don’t get it wrong with fast charging and slow charging. 7kW? 270kW?

After purchasing an electric vehicle, the planning of charging becomes the most important thing, because the charging of electric vehicles is accompanied by time costs, density differences (such as towns and cities), regional differences, etc. After all, the density and maturity of charging stations at this stage are not high enough. Like a gas station, if the charging plan for commuting or traveling is not planned in advance, it may cause mileage anxiety in the mild case, or stop on the road without power, which may happen.


Secondly, according to the power level, charging can be divided into fast charging and slow charging. Generally speaking, the common AC type SAE J1772 and CNS 15511-2 are regarded as slow charging specifications, and the highest power ranges from 6.6kW to Between 17.6kW, and fast charging generally refers to DC CHAdeMO, Tesla's Super-Charger, Porsche's 800V fast charging system, etc., with a power between 50kW and 270kW. The vast majority of household systems are slow-charging systems, and the cost of fast-charging systems is quite high at present.


For charging planning, first clarify where your "home field" is. The most common ones may be the first floor of Mall, private parking lots of collective housing, public parking lots, etc. If you want to build your own private charging device , most of them belong to the slow charging system. In addition, the current lithium-based chemical battery system will reduce its life to a certain extent under the high power of fast charging. Although the battery management program and control system can slow down this phenomenon, it is still unable to completely overcome this problem.


Therefore, when the vehicle needs to be parked for a long time (such as overnight), the slow charging system should be selected first to fully charge the power slowly, which can reduce the loss of battery life on the one hand, and achieve the combination of "parking and charging" formula effect.


As for when going out, fast charging stations should be prioritized in charging planning. After all, in terms of time cost, the time between fast charging and slow charging may be ten times or even dozens of times different. If you move across regions, you should basically plan 1 -More than 2 fast charging station routes can ensure the safety of battery life.

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