December 5, 2023

What Factors Affect Home EV Charging Speed?

5 Min. Read

The popularity of home charging continues to surge. With the allure of convenience, cost savings, and independence from public charging stations, many EV drivers are opting to install an at-home charger. However, it’s crucial to first understand your charging needs. One key issue to remember is the array of factors that can affect home charging speeds. In this article, we cover the key factors that can impact your EV charging speed and electric vehicle experience, helping you find the best charging solution for your unique needs.

Vehicle-Related Factors in Charging

Characteristics of batteries and vehicles can influence charging speed, including battery capacity, charging current and speed, and various chemical components.

Battery Capacity, Charging Current, and Charging Speeds

Generally, the higher the EV battery capacity, the longer the charging time required. Consider this simplified analogy: filling a 60-gallon barrel (representing the battery) with water (electrons) from a hose flowing at 2 gallons (current) per minute. At that rate, the barrel will fill in 30 minutes. If you change the current in the same hose to 3 gallons per minute, the barrel will fill in 20 minutes.

For optimal performance, it’s essential that your charging station, EV battery, and onboard charger are in harmony, so check with your dealer about the capacity of your EV battery and the optimal charging current. Understanding these aspects of your EV is crucial for efficient charging and will help you determine the best charging options for your vehicle and driving needs.

You should also consult with your licensed electrician who will be installing your at-home EV charger prior to purchasing your Electric Vehicle Supply Equipment (EVSE), also referred to as an EV charger, as your panel capacity may also limit the amperage you will have available for EV charging. Your electrician should perform a load calculation to determine available panel capacity and can further advise you on any additional infrastructure needs to support installing your EV charger, such as a panel upgrade, sub-panel, or load management device.

Battery Chemistry

The most common EV batteries use lithium ions to function, and the chemistry of lithium-ion batteries dictates charging behavior. With lithium-ion batteries, as the charging level rises, the charging rate falls. This means that the last 20% of charging takes longer than the first 80%.

It’s important to note that pushing batteries beyond their ability to absorb a charge can result in battery deterioration. Therefore, keeping your EV battery charged between 20% and 80% is recommended for the best battery life.

The good news is that ongoing research on new materials for faster charging is showing promising results.

Onboard Charging Capacities and Charging Speeds

The charging station itself does not charge the battery. Instead, it converts AC power from your panel into DC power, which is then sent to your EV’s onboard charger to charge the battery. An onboard charger delivering more kilowatt-hours (kWh) of current will charge your vehicle faster than a lower-capacity one, with all other variables held constant.

With a higher-capacity onboard charger, it’s important to size your charging station to deliver current to the onboard charger safely and within specifications.

Home Charging Infrastructure

There are several points to keep in mind when planning and installing your home EV charger. These include understanding charger capacity and wiring requirements.

Charging Equipment Capacity

Chargers vary in capacity, which is measured by kWh output. High-capacity chargers may require higher-amperage circuits. It’s important to know the power supply requirements of your charger beforehand since more powerful ones may need more amperage and a panel upgrade.

Three Charger Levels and Speeds

There are three levels of chargers. Level 1 is the slowest, simplest, and cheapest type. It typically takes 20–43 hours to charge to 124–249 miles and requires only a standard 120V receptacle. However, for most users, this duration is impractical since their EV will likely be offline for over 24 hours.

Next is Level 2, the most practical option preferred by more than 80% of EV owners. Requiring a dedicated 240V AC circuit and a hardwired connection or specialized NEMA 14-50 outlet, these chargers can typically charge an EV to 124 miles in 5 hours. Their cost is also affordable, making Level 2 the most sensible choice for home charging, offering the convenience of overnight charging and significant savings over public charging options.

Level 3, Direct Current Fast Charge (DCFC), is the most powerful, complex, and expensive type. These units require direct current (DC) at between 50 and 350 kWh and can charge an EV to 100 miles in roughly 30 minutes. However, the downside is that its high current flow can degrade your EV with frequent usage over time.

Hiring a qualified electrician with EV charging installation experience and certification for your installation service is important, especially for Level 2 or Level 3 chargers. Permits are usually required, and these projects involve high-voltage work, which can lead to electrical fires, damaged technology, and even fatalities if the charger is improperly installed or the wrong equipment is used.

Electrical Wiring and Circuitry

Note that the high voltage constantly moving through your charging system exerts constant stress on wiring, panel circuits, and other components. Over time, low-quality wires and components may fail to conduct current properly and slow down charging speed. Therefore, it’s crucial to use high-quality parts and materials to ensure trouble-free performance. Retrofitting wiring and circuits is time-consuming and expensive, another good reason to use a qualified EV installer.

External Influences

Voltage fluctuations in the grid and extreme temperatures can impact charging speed by introducing “noise” into the current.

Grid Power and Voltage Fluctuations

Grids may experience dips or outright drops in voltage. In equation form, kWh=(AmpsVoltsHours of Usage)/1000, so a voltage reduction will cause a proportional kWh reduction. Since kWh drives charging speed, charging time will increase.

Introducing battery storage and an inverter into your charging setup can eliminate voltage fluctuations. The battery and inverter flow AC power at a constant voltage and clean up the current. The further addition of a microgrid with solar and battery storage will guard against power fluctuations and can provide essentially “free” renewable power.

Temperature and Environmental Conditions

Extreme temperatures affect battery performance and slow charging speed. Higher heat speeds up battery chemistry beyond its effective range, and extreme cold slows battery function below that range.

The optimal range for charging is between 32° and 68°F. Keeping your EV in a garage is a good way to mitigate temperature effects. Otherwise, you will need to adjust your charging time accordingly.

We’ll Advise You On Your Charging Speed Selection

Selecting and installing an EV charger with the correct charging speed is crucial to successful EV ownership. EV technology is still evolving, so seeking expert advice makes sense. Qmerit can help because electrification and EV charging are our business. With over 269,000 EV chargers and 18,500 battery storage systems installed, 53,000 solar integrations, and 86,700 electric panel upgrades, we are uniquely qualified to help you succeed in selecting and installing the optimal charger.

Schedule your installation with Qmerit today to ensure a smooth, successful project, and great EV charging performance for your future.

Author: Greg Sowder Greg Sowder President, Qmerit Network