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Simultaneous Charging: Less Equipment, More Happy Customers

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By Jeremy Whaling, Senior EVSE Engineer
Mar 8, 2023

Electric vehicle (EV) fast charging technology is evolving rapidly to meet the needs of the incoming growth of electric vehicles on the road. The next generation of EV fast chargers offers more power—EVgo is regularly installing high-powered 350kW chargers—as well as power sharing capabilities to maximize charging options for more drivers.  

Some fast charging equipment can share power between two different charging dispensers; however, newer equipment allows a single charging dispenser to share power between its connectors. This technology, called simultaneous charging, allows one charging dispenser to serve two EV charging stalls, meaning two drivers can plug in at the same charger.  

Deploying simultaneous chargers allows EVgo to build larger sites that can charge more vehicles while using less equipment, thereby increasing the “EV charging density capability” of each station and expanding access to fast charging. 

How does simultaneous charging work? 

A DC fast charging station may have two connectors, but for many chargers only one is operable at a time. The other connector shuts down when the available power is going to the one in use.  

A simultaneous charger works by allowing two EVs to share a charger’s power between two connectors on the same charging dispenser. When one connector on a simultaneous charger is in use, the EV has access to the full power of the charger. When both connectors are in use, the two EVs share the full power of the charger.  

It’s important to note that just because your EV has “access” to a certain amount of power, it doesn’t always mean that your vehicle can accept that level of power. Many variables determine the speed at which your car can charge. You can read more about what determines your charge speeds in our EV101 series 

Let’s look at charging scenario using a 350kW simultaneous charger that EVgo is installing across the country. If one vehicle uses the charger, that car can theoretically access the full 350kW of power (e.g., the GMC Hummer EV can charge at or near that power level and the Porsche Taycan can reach a 270kW peak charge rate, but most EVs on the road today can’t pull anywhere near 350kW).  

But if a second car pulls up to the charger and uses the other open connector, then each car now has access to 175kW of power, which can still give you somewhere around 100-150 miles in 15 minutes if the vehicle can accept that level of power. 

Why is EVgo focusing on power sharing and simultaneous charging? 

EVgo is installing 350kW high-power chargers with power sharing and simultaneous charging capabilities because we are building the infrastructure for the future today. Dynamic power sharing allows for power to be allocated to the vehicles that can make the most of it. The end result is a group of vehicles that can move through the chargers faster. 

As battery technology improves, EVs will likely be able to charge much faster – accepting closer to 350kW of power. EVgo is already installing charging units that can deliver 350kW to a single stall so that current and future EV drivers will be able to charge as fast as their vehicle allows.  

Some 350kW charging units, like the Signet chargers that EVgo deploys, can share power between two different charging dispensers – not just between the connectors like other simultaneous chargers. With the Signet charging units, power is dynamically shared between dispensers at increments of 25kW, allowing a wider variety of power splits. Check out the following image to see all the components of a fast charging site. 

But from the perspective of a charging network owner and operator like EVgo (we purchase the expensive equipment and often pay rent for the parking stalls the chargers occupy), simultaneous charging and power sharing between connectors is an effective way to maximize the energy a single charging dispenser can deliver, helping us serve customers more efficiently.  

With all the work and capital that goes into installing and operating a charger, from permitting, trenching and wiring to utility coordination etc., we can double the number of vehicles served with each charging dispenser. 

What do EVgo customers need to know about simultaneous charging? 

If you see the message “Simultaneous Charging Available” on the screen of an EVgo charger (like the one above), then you’re at a charger with simultaneous charging capabilities.  

Another way to find this capability is to look for a double arrow symbol shown next to a 350kW charger in the EVgo app. 

You’ll also be able to see which connectors are available within the app. When charger icons are green, the connectors are available; when charger icons are red, the connectors are already in use and not available.  

In this graphic, the top row shows that both connectors are available; the middle row shows that one is available, and the bottom row shows that neither are available. 

If you’re the only driver using a simultaneous charger, you’ll have access to up to 350kW. For example, the following charger screen shows that only Connector B is being used and that the “Max” power available under the “kW” column is at 349kW.  

However, if another driver is using the other connector at the same time, which is called a “shared session,” the available power is now limited to 175kW…that’s still much higher than the peak charge rate of most EVs on the market today. 

The screen below shows an example of shared session where both Connector A and Connector B are in use and they’re each delivering ~45kW (even though 175kW is available to each).  

Note: Power delivered means how much power is actually going from the charger into the vehicle…available power is how much power the charger is able to deliver to the vehicle. If the power delivered is less than the available power of the charger, the vehicle’s battery is the constraint. 

In conclusion 

EVgo works closely with its equipment supplier partners to deploy solutions that are efficient and enhance the charging experience, which helps to accelerate EV adoption. EVgo Autocharge+ is the most recent example of an innovative solution that helps drivers start a charge even faster.  

With simultaneous charging, EVgo is building the infrastructure to meet today’s charging demand with less equipment while also creating a network that can support the EVs of the future.