AC current vs. DC current: what's the difference?

February 21, 2022

Charging your electric car on alternating current (AC)

Available as standard on all models on the market, AC charging can be used for single-phase or three-phase charging. In most cases, it is intended for slow and accelerated charging (2.3 - 22 kW).

When an electric car is recharged from a household socket or AC outlet, the electricity is first converted by a converter into direct current before being injected into the battery. The power of the converter varies from one car manufacturer to another. In the majority of newly-marketed electric cars, it ranges from 7 to 11 kW.

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Recharging time then depends on the power and type of current accepted (single-phase or three-phase) by the car's converter. These two characteristics will determine the DC charging time.

In a single-phase current, electrical power is delivered by a single phase, whereas in a three-phase current, power is delivered by three phases.

Example of AC recharge time depending on the converter :

• A car with a 7 kW on-board converter (single-phase) that connects to an 11 kW terminal (three-phase) will only be able to accept one phase from this three-phase terminal. So the car charges at 3.7 kW (11 kW divided by 3).

• On the other hand, a car with an on-board 11 kW (3-phase) converter that connects to an 11 kW (3-phase) terminal will charge at 11 kW.

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For example, here are the charging times for a Renault Zoé:

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⚡️ Charging your electric car with direct current (DC)

For electric cars, direct current is used for so-called "fast" and "high-power" recharging. In this case, the charging stations feature built-in converters that transform AC mains current into DC current. This current is then injected directly into the battery, without having to pass through the car's inverter.

Charging time depends on the car's capacity. A car that can be charged at a 150 kW charging point, but only has a 100 kW charging capacity, will only charge at 100 kW.

Here are the DC charging times, using the previous example of a Renault Zoé:

🚀 Bump's vision: fast charging in the heart of the city

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DC terminals are therefore much more powerful, but also more complex and more expensive than AC terminals. For this reason, they are often intended for "service station" use.

Today, 95% of urban infrastructure in France is for slow recharging (7kW), which takes 3 hours or more to recharge 100km. This customer experience doesn't meet user expectations, and prevents high turnover at the charging station. What's more, today, the cost of an on-street fast charge is 15 to 30% more expensive than a full tank of petrol.

Bump's aim is different: to enable our customers to find fast charging, at an attractive price and bookable right in the heart of the city. Today, we're the leader in fast-charging in Paris.

• We install and finance 100% of our terminals
• Terminal maintenance is handled free of charge by our team, with an availability rate of 98%.
• We offer a monthly remuneration to the landowner

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So, if you're interested, contact us below and don't hesitate to visit our website.

Source: Renault official website