Your questions answered: How to design electric vehicle charging stations

Electric vehicle insights

• Gain an awareness of the different electric vehicle charging station levels and capabilities.
• Review several responses to questions posed during this webcast.

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As the world continues adopting electric vehicles (EV), there are several factors to consider when designing the electrical system to support a customer’s site deployment. Because estimates show that more than 18 million EVs will be on the road by 2030, electrical engineers need to understand the challenges and solutions.

Electrical engineers designing EV supply equipment (EVSE) and systems to incorporate and support EV charging must be aware of the basics of charging as well as how the customer plans to use the charging stations. From this, the electrical engineer must be well versed in not only the EV charging hardware (Level 1 and Level 2 AC chargers, DC fast chargers), but also in the software platforms (charger network operators) that provide the functionality customers seek.

Read additional responses that did not appear with the June 13, 2023, webcast.

Expert presenter: Mitch Simmons, PE, Technical Marketing Lead, Eaton Corp.

Question: What does the 0.6 factor represent in the example assumption on slide 9?

Answer: The 0.6 factor corresponds to an approximate kilowatt-hour (kWh) estimation for charging from a 20% state of charge to an 80% state of charge in a vehicle.

Question: Do the same rules apply to Level 2 portable charging stations? Is a power management system necessary to qualify for government incentives?

Answer: Yes, Level 2 portable chargers are encompassed by the 2023 National Electrical Code (NEC) article 625. Unfortunately, I cannot provide a definitive answer, as it might depend on the source of incentives (federal, state, local, etc.).

Question: If an Energy Management System (EMS) is employed, should the Electrical service be sized for each electric vehicle (EV) charging station’s maximum output, or is there a manufacturer-recommended calculation based on the total number of EV charging stations per NEC 625.42(A) and 750.30?

Answer: NEC 625.42(A) states that the feeder should not exceed the maximum load allowed by the Automatic Load Management system. As per the 2023 NEC, section 625.42(A) permits sizing the system based on the EMS’s maximum load.

Question: Is there a specified maximum distance for a remote readily accessible disconnect?

Answer: The 2023 NEC section 625.43 does not offer distance guidelines.

Question: For stations exceeding 60A, is a disconnect required for each station or for the entire EV station panel?

Answer: According to the 2023 NEC 625.43, each individual EV charger exceeding 60A or having more than 150V to ground necessitates a disconnect.

Question: How do you determine the appropriate breaker and branch feeder size?

Answer: The 2023 NEC article 625.40 covers branch circuits, while 625.41 addresses overcurrent protection.

Question: When planning the infrastructure for electric vehicle (EV) chargers, what type of diversity can be used for the electrical loads?

Answer: The 2023 National Electrical Code (NEC) articles 625.40, 625.41, and 625.42 cover this extensively. In summary, an EV charger is treated as a continuous load for calculations, unless one of two methods in 625.42 is applied to limit the rating. These methods involve an Energy Management System (EMS) in line with 750.30 or an EVSE with adjustable settings and restricted access per 750.30.

Question: Are ground fault circuit interrupter (GFCI) protections necessary for Level 2 and fast DC chargers?

Answer: As per the 2023 NEC article 625.54, GFCI is required for any receptacle meant for EV charger connection.

Question: In residential design, are EV chargers classified under 220.82(B)(3), or are they treated as separate continuous loads, with optional feeder/service load calculations?

Answer: The 2023 NEC Part III article 220.57 addresses EV Supply Equipment (EVSE). The load should be calculated at 7200W or the nameplate rating of the EVSE, whichever is larger.

Question: How do NEC residential calculations account for an EV charger? Do they fall within the 40% calculation for a single-family optional calculation?

Answer: The 2023 NEC Part III article 220.57 addresses EV Supply Equipment (EVSE). Load shall be calculated at 7200W or the nameplate rating of the EVSE, whichever is larger.

Question: One slide mentioned the assumption of 3 miles per kWh. Is that accurate, or should it be 3 kWh per mile?

Answer: The correct assumption is 3 miles per kWh. For instance, a highly efficient EV like the Tesla Model 3 RWD, according to Environmental Protection Agency, has an efficiency of 25 kWh per 100 miles, translating to 4 miles per kWh.

Question: What process do you take to make recommendations for a design that anticipates expanding future capacity for new construction and existing buildings?

Answer: Several considerations are involved, such as the client’s timeline and goals. These must align with utility service availability for current and future EV charger expansion. In some regions, building codes stipulate the percentage of new parking spaces for EV charging. For existing buildings, assess current load, growth plans, and determine necessary infrastructure based on converted parking.

Question: Does this imply that all vehicles will now feature Tesla-compatible charging outlets?

Answer: As of now, only Ford and General Motors Corp. have announced the transition to NACS.

Question: Does the cloud-based load management system adhere to NEC 750? How does the system respond during network downtime?

Answer: Based on our assessment of the 2023 NEC article 750, we believe our Cloud Network Manager (CNM) is compliant. However, local Authorities Having Jurisdiction (AHJs) might interpret this differently, and the code is evolving. Consult your local AHJ before specifying a cloud-based EMS for this purpose.

Question: For bidirectional chargers, does the equipment include a Utility Lockable disconnect to halt power flow into the grid?

Answer: The 2023 edition of NEC 625.48 covers interactive equipment for bidirectional chargers. Depending on power export capabilities, follow article 702 or 705.

Question: Is GFCI protection mandated for the branch circuit providing power to a hardwired charging station?

Answer: As per the 2023 NEC article 625.54, GFCI is required for any receptacle meant for EV charger connection. Hardwired connections are not specifically mentioned for GFCI.

Question: Does a hardwired charging station necessitate a GFCI circuit breaker?

Answer: As per the 2023 NEC article 625.54, GFCI is required for any receptacle meant for EV charger connection. Hardwired connections are not specifically mentioned for GFCI.

Question: For commercial Level 2 and Level 3 EV charging systems, is ground fault protection needed for the power source to the EV chargers?

Answer: As per the 2023 NEC article 625.54, GFCI is required for any receptacle meant for EV charger connection. Hardwired connections are not specifically mentioned for GFCI.

Question: What is the advantage, and how does it differ, between an ac and dc charger?

Answer: Currently, no clear superiority exists when comparing ac and dc charging.

Question: How many charging stations are appropriate for a 700-employee company?

Answer: The adoption rate depends on location and company type. Rates can vary from 1 to 20% or more. For a rough estimate, suggest EV charging for at least 5% of employees.

Question: When designing power for charging stations, should communication to the stations be part of the design? Or do charging stations utilize cellular communications?

Answer: Communication design is crucial. Even with cellular connectivity, consider signal strength at the site. For reliable connections, Ethernet or Wi-Fi to an access point may be preferable.

Question: Must dual charging stations always necessitate two circuits for power?

Answer: Dual port Level 2 ac charging stations typically support single and dual inputs.

Question: Do charging stations generally employ a Standard Open Protocol Serial Communication interface for EMS integration, like BACnet?

Answer: Commonly, EV chargers utilize the Open Charge Point Protocol (OCPP) or proprietary protocols like Modbus or BACnet.

Question: Regarding NEC diversity, will EV charging be incorporated? I recently worked on a project with 55 EV stations, where load diversity was lacking.

Answer: For significant installations, 2023 NEC article 625.42(A) allows Energy Management Systems according to 750.30 to limit power to EV chargers.

Question: What suggestions exist for adding numerous EV chargers to existing building facilities? Often, a new electrical service is needed, such as 3000A gear.

Answer: For sizable installations, 2023 NEC article 625.42(A) permits Energy Management Systems according to 750.30 to limit power to EV chargers, potentially reducing required service size.

Question: Is there a maximum size for LV 2 chargers in KVA? Is the industry aiming to maximize LV 2 charger power?

Answer: In North America, Level 2 maxes at 80A, equivalent to 19.2kW at 240VAC.

Question: Are Level 2 stations interchangeable? If infrastructure is being designed while choosing charger manufacturers, what is the approach?

Answer: From an electrical standpoint, Level 2 stations are interchangeable. But consider physical installation, as wall mount chargers are simpler to swap than pedestal ones.

Question: Is it recommended to use Tesla standard plugs or alternatives? What is suggested for a single high-current station?

Answer: For a high-current DC fast charger, choose a system supporting both CCS and NACS as dual port stations.

Question: With Level 3 charging mentioned in Los Angeles, is a Level 3 charger standard forthcoming?

Answer: Level 3 often refers to dc fast charging. There is no imminent standard for it.

Question: Is a Level 3 charger standard being developed?

Answer: I am unsure about this. Level 3 often refers to dc fast charging.

Question: Can you comment on Ford and General Motors Corp. adopting Tesla chargers for their future vehicles?

Answer: I cannot provide additional information beyond their announcements.

Question: Does Eaton’s Charger Network Manager handle an unlimited number of EV chargers?

Answer: The Eaton Charger Network Manager can manage numerous EV chargers. Reach out to your local Eaton representative for specifics.

Question: In a Brazilian project with 380/220V, is 220V L-N acceptable for Level 2 chargers?

Answer: European-spec Level 2 chargers using Type 2 (Mennekes) plugs might support this.

Question: Can you speak about charging stations for public use provided by a private company and how the utility looks at the resale of their power.

Answer: Many regions have adjusted their regulations to allow for monetizing charging sessions using $ per kWh. However, in those regions where this is not allowed, monetization can typically be achieved by using a time-based policy ($ per minute) or flat fee. But in all cases, you will need to verify with your local utility commission.

Question: In locations where the serving utility prohibits resale of electricity, is monetizing a public charging station possible?

Answer: Many regions have adjusted their regulations to allow for monetizing charging sessions using $ per kWh. However, in those regions where this is not allowed, monetization can typically be achieved by using a time-based policy ($ per minute) or flat fee. But in all cases, you will need to verify with your local utility commission.

Question: Do vehicles have multiple plugs to work with both level 2 and dc fast charging?

Answer: Most plug-in vehicles for North America support J1772 and CCS. The Nissan Leaf supports J1772 and CHAdeMO. Tesla uses their NACS, but they do offer adapters to allow their EVs to use J1772 and CCS. I have a condo association looking to install Level 2 charging capabilities to 35 parking spaces in a parking garage.

Due to the limited service available (approximately 400amps @ 120/208v – 3 phase) I am trying to estimate how many chargers I can place on a service this size. Also, in answering this question I understand that there are current limiting capabilities that could be networked together.

Multiple charging stations can have their power limited in accordance with 2023 NEC article 625.42 (A) using an Energy Management System in accordance with 750.30. NOTE that the EV charging stations also need to support load management in the hardware.

Question: Did your examples include bidirectional power flow?

Answer: No, the examples did not include bidirectional power flow.

Question: Are there any level 2 chargers available at 480V?

Answer: Not currently.

Question: Are there any 208V 3 Phase chargers?

Answer: Not currently.

Question: Do you have any recommendations for when and how to specify OCPP?

Answer: OCPP can be included in the EV charging specifications. It can be part of the technical requirements list or could be part of the connectivity section.

Question: For fleet customers, how do you provide flexibility to maximize interchangeability of vehicles and charger plug types?

Answer: Outside of Tesla and the Nissan Leaf, today’s plug-in vehicles for North America support J1772 and CCS. The Nissan Leaf supports J1772 and CHAdeMO. Tesla uses their NACS, but they do offer adapters to allow their EVs to use J1772 and CCS. So, it will depend on which specific vehicle will be used in the client’s fleet. Ford and General Motors Corp.’s recent announcement for support of the NACS will change those models sometime in 2025-2026.

Question: The breaker type charger – What’s the rough cost for one of those vs one of those typical level 2 chargers we see around? Like half the cost? 3/4ths the cost? 1/4th the cost?

Answer: Please connect with your local Eaton representative, and they will be able to assist with your question.

Question: Are you seeing a standardization in plug-types for EV charging as the systems become more ubiquitous like NEMA standardization?

Answer: Plug types for EVs are evolving. There are currently 4 options in North America: J1772, CCS1, CHAdeMO and NACS (Tesla). With the recent announcement of Ford and General Motors Corp. transitioning to NACS, the next few years will be interesting to observe if NACS becomes the prevailing standard over J1772 and CCS1.

Question: Are these chargers designed to be generic to adapt to all vehicles?

Answer: The short answer is yes, but as this market continues to advance, there will be some growing pains. As of this answer, the charging stations are designed to support J1772 (L1 & L2) and CCS1 & CHAdeMO (DC fast charging). However, Tesla recently opened and released their connector as the NACS. And most recently, both Ford and General Motors Corp. have announced they will transition to NACS.

Question: What are the differences between standard charging and fast charging stations? Are there any solar charging stations on the market yet? What does the charging station management software do?

Answer: Solar charging stations generally rely on some sort of grid connection because they simply cannot generate enough power in a timely fashion to charge more than 1 EV, so while there are solar EV charging stations, they are not really practical in the absence of a grid connection and/or adjacent battery energy storage capabilities.

The charge station management software serves several key functions, including managing access to charge stations, establishing pricing and processing transactions for station use, remote monitoring and reporting on station status and usage and load management. Not every customer needs all of these features and functionality so you should definitely ask your customer what they are trying to do with EV charge stations so that you can sell them on the features that matter to their application.

Question: Can you use solar to power the charger?

Answer: Solar charging stations generally rely on some sort of grid connection because they simply cannot generate enough power in a timely fashion to charge more than 1 EV, so while there are solar EV charging stations, they are not practical in the absence of a grid connection and/or adjacent battery energy storage capabilities.

Question: Fast DC = Level 3, right?

Answer: Technically, level 3 was originally intended to be 3-phase AC charging, but it is commonly used to describe DC fast charging. So, if you see level 3 charging referenced, they are most likely referring to DC fast charging.

Question: Are there adapters for the different types of charger connectors?

Answer: Tesla offers adapters for their EVs to use J1772 and CCS. As of this answer, there are not adapters for using J1772 or CCS with NACS. So currently, non-Teslas cannot use NACS, although the recent announcements from Ford and General Motors Corp. indicate that adapters are forthcoming for current plug-in EVs from those manufacturers.

Question: Did you intend to include a 1.25 factor on your calculations since the chargers are considered continuous?

Answer: The 125% would apply to the overcurrent protection device, 2023 NEC 625.41.

Question: What is 253 kW?

Answer: The 253 kW came from the previous slide where it showed the level 2 AC charger calculations. In full transparency, it was the total balanced load of the level 2 chargers which in that example was showing an imbalance.

Question: How does the J1772 know what size breaker is feeding it? Or put in another way, how does the car know not to overload the breaker when charging?

Answer: The charger has a fixed or adjustable rating, and the circuit breaker needs to be sized for the rating of the EV charging station.

Question: Is the distribution transformer need to be upsized for DC Fast charger due to harmonic currents?

Answer: The DC fast charger manufacturer should be able to provide the harmonic distortion caused by their equipment. That information can then be used to specify the correct K-factor or a full harmonic mitigating transformer. Additionally, harmonic correction units (HCU) could be applied in situations where the combined harmonics are high.

Question: If using the Eaton EV Smart Breaker Charger panelboard. How does the customer can monetize and control charging stations?

Answer: The EV Smart Breaker Charger can communicate either via API or via OCPP. If using the Eaton CNM platform, a QR code label would be applied at the parking spot associated with the EV Smart Breaker Charger. The driver would scan the QR and provide payment information to access the charging station.

Question: Are there demand factors regarding the number of (Day One and future) chargers when calculating the service size?

Answer: There is currently not a demand factor for EV chargers. However, as a design philosophy, this would be a combination of balancing customer needs with cost and practicality.

Question: What is the max ampacity you can design to?

Answer: This becomes more of a bus ampacity limitation of the switchboard structure.

Question: What is the typical installed cost for a level 2 40amp and 80 amp charging station? I am only asking for equipment.

Answer: This can vary significantly depending on the manufacturer and feature set. It also can vary based on-site conditions and how much work is involved.

Question: You mentioned that IECC 2021 has removed EV charging requirements. When was it removed? The last I checked, there was verbiage with requirements for EV (count of chargers required, how many must be EV-charger ready, etc.).

Answer: This excerpt is from the 2021 Electric Vehicles and Building Codes: A Strategy for Greenhouse Gas Reductions: This document recommends placement of EV charging requirements within the IECC. While EV charging requirements were ruled out of scope for the 2021 IECC, the new scope and intent for the IECC moving forward (as defined by the Code Council board of directors) includes avenues for the inclusion of energy and GHG reduction requirements like EV charging. EV charging requirements could also be in the IBC with the current EV requirements in Section 406.

Question: How will these chargers be integrated into the smart grid of the future?

Answer: This is an excellent question and unfortunately will take too long to type a response here. This requires a more holistic view into microgrids and V2X technology.

Question: Do consumer level 2 charging stations include integral controls for load management, or does load management require additional infrastructure?

Answer: This is dependent on the manufacturer of the EV charging stations and how they choose to implement load management.

Question: What is the quickest time you can charge a standard vehicle, and how far miles can be driven with a fully charged vehicle?

Answer: This is dependent on the specific EV and its capabilities.

Question: Do you typically see a CAT6 cable run to the charger, or do most chargers have a cellular connection for payment services?

Answer: This is more of a consideration for site conditions and what is practical for the site host.

Question: Is fast charging going to affect the overall battery life?

Answer: This is more of a question for the EV manufacturer and how they manage their battery system.

Question: How common is the use of local batteries (or ESS) to maintain peak demand?

Answer: This starts to look at microgrids to help support EV charging. I have read of some sites using ESS to supplement their dc fast chargers.

Question: Should designers specify OCPP somewhere in electrical drawings?

Answer: This would depend on the firm’s best practices for their drawing packages, but yes, OCPP could be included in the electrical drawings, potentially as a key note with the connectivity method of the EV chargers.

Question: For supply voltage, does this include 208V/1P or 208V/3P?

Answer: Typical level 2 EV chargers use residential 120/240V, but in commercial applications, they can be connected across 2 phases of a 3-phase wye-connected system (208Y/120VAC). Other supply voltage configurations would need to be confirmed by the EV charger manufacturer.

Question: What diversity factor can be used for multiple charging stations at a specific site?

Answer: Unfortunately, demand factors are not allowed for EV charging stations. Multiple charging stations can have their power limited in accordance with 2023 NEC article 625.42 (A) using an Energy Management System in accordance with 750.30. NOTE that the EV charging stations also need to support load management in the hardware.

Question: Assuming a level 2 charger was installed per design (wire size, OCPD, load capacity is optimal at the panelboard and charging station), what other possible factors can contribute to an upstream circuit breaker showing a high-temperature reading while charging an EV car?

Answer: Unfortunately, several factors can lead to high temperatures on the breaker, and these factors may not be directly related to EV charging. Further investigation would be needed to determine the root cause.

Question: With charging stations typically located farther away from the building, do you often run into issues with Voltage Drop and equipment lug sizes when upsizing wiring? Has there been any consideration on the manufacturer’s side to address this?

Answer: Voltage drop is a consideration when laying out the routing for EV charging. I cannot speak for other manufacturers, but we do try to look at lug sizes to allow for some larger cable sizes. Please refer to the installation manuals for clarification on supported cable sizes.

Question: Can we consider demand loads using an EMS or ALMS system in designing the electrical infrastructure for EV charging, in lieu of considering connected loads for service?

Answer: Yes, if the EMS meets the requirements of 2023 NEC 625.42 and 750.30.

Question: Can you install most chargers with 240 ratings on 208V systems? In other words, is there a risk of damage like if you install a 240V motor on a 208V system?

Answer: Yes, most Level 2 ac chargers can be applied at 208V line to line; however, always check with the manufacturer if the data sheet or installation manual does not provide this information.

Question: Is there an option for an outdoor panelboard (possibly pedestal-mounted) with integral EV charging breakers?

Answer: Yes, this is possible.

Question: For bi-directional power flow, does the feeder breaker for the EV charger need to be suitable for reverse feed?

Answer: Yes, this is possible.

Question: Do you need an EV charger management system regardless of the quantity of chargers if the desire is to monetize the charging?

Answer: Yes, the charger management system handles the backend payment processing and authorization for charging.

Question: Do the Eaton Smart EV breakers meet the GFCI requirement?

Answer: Yes, the Eaton EV Smart Breaker Charger has a built-in ground fault as it is also a 32A Level 2 AC charger.

Question: Is there a shut-off control to turn the charging system off when the batteries are fully charged?

Answer: Yes, this is handled through the EV itself using the control pilot signal line in the connector.

Question: I saw the voltage is 240V but only single pole, aren’t these usually 2P? Do these charging stations also have a shut-off safety component so it does not overcharge the batteries?

Answer: You are correct, that was a typo in the presentation. 240V & 208V connections would be 2-pole. For AC chargers, the EV’s onboard charger (OBC) is managed by the EV’s battery management systems (BMS). The BMS will tell the OBC when to turn off and whether to throttle charging to protect the EV’s battery.

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