Making Changes for Charging Electric Vehicles

by Matt Woo, P.E., RCDD, LEED AP BD+C

This article is part of Wood Harbinger’s newsletter series.

Electric vehicles  can be a great means of transportation which help reduce emissions on the environment, save fuel, and reduce maintenance costs.  They are also very quiet to drive and have fewer moving parts to maintain.  However, they aren’t without maintenance entirely, though, as the batteries inside electric cars have a finite amount of life in them before they need to be replaced.  Also, compared to gas vehicles, electric vehicles  can’t travel as far before needing to “fuel up.”  Currently, most electric vehicles have a range of around 100-150 miles on a single charge.  Depending on driving style and where you live or are traveling, EV  range can also greatly vary, especially in below-freezing weather, where electric vehicles lose around 20% to 50% of their range.

Before the battery runs down, an electric vehicle must be recharged.  Compared to gas vehicles, which take minutes to refuel, electric vehicles can take around 20-minutes up to eight or more hours to refuel, depending on the amount of discharge, type of charging used, as well as the kW rating of the onboard charger inside the car.  A charger’s output is measured in “miles of charge per hour”.

Charging Speed

Electric vehicle charging or fueling can be accomplished slowly or much quicker, but with a tradeoff in terms of building infrastructure requirements.  Level 1 charging is the slowest, connects through a standard 120V outlet, and has a maximum charging output of up to 1.9kWH, so this charging can refuel an EV battery at a rate of only about 2-5 miles of charge per hour of charging.  Level 2 charging uses 240V power, has an Electric Vehicle Service Equipment (EVSE) plug to connect to the electric vehicle’s charging port, and has a maximum charging output of up to 7.2kWH, which allows faster charging at a rate of about 10-25 miles of charge per hour of charging.  For Level 1 and Level 2 charging, the charging device “on-board charger” is factory-installed on the car and is typically sized for 6.6kW for BEV’s and 3.3kW for PHEV’s.  In Level 3 charging “DC Fast Charging”, the charging device “charging station” comes with its own internal high-powered AC/DC converter, which enables it to supply between 40kWH and 90kWH of energy to refuel the battery.  With this charging method, an electric vehicle that comes installed with a compatible CHAdeMO or J1772 combo charging port (like the Nissan Leaf or BMW i3) can add around 50-90 miles of range to their batteries for every 20 minutes of charging.  In Tesla’s Level 4 proprietary “superchargers”, a Tesla EV can charge up to 350 miles of range in a mere 20-minute span.

Growth Requires New Infrastructure

With electric vehicle use in the United States expected to grow steadily to account for about 15% of the United States car market by 2025,  it is becoming increasingly important for building owners to review their building’s electrical infrastructure to determine if they have ample capacity and infrastructure to support future electric vehicle charging stations. Wood Harbinger has worked on a few electric vehicle charging station installations in recent years. At St. Mary Medical Center in Walla Walla, we designed power distribution to add two Level 2 charging stations in parking lots. At the Seattle Municipal Tower, Wood Harbinger assessed the existing conditions and electrical infrastructure upgrades needed to support 26 new electric vehicle charging stations in the parking garage. Our investigation revealed that an existing switchboard had the capacity to serve the new loads, and we split the loads among the three panelboards to maintain balance. We also transformed the garage’s 480/277 volts system to 240/120 volts to serve the charging stations. We also added seven duplex receptacles in the garage to support charging station maintenance. At the Eastgate Park and Ride in Bellevue, Wood Harbinger provided calculations and design to add a new electric service to feed five 500kW overhead electric bus charging stations.

Demand Response Systems

Buildings with a limited electrical capacity and infrastructure may only be able to accommodate a few 120V Level 1 charging stations and even fewer 208V or 240V Level 2 charging stations.  For example, a 400A, 208Y/120V, 3PH, 4W building electrical panel with 100A of spare capacity may be able to serve six 120V Level 1 charging stations or three 208V Level 2 charging stations. If a building’s electrical infrastructure is under-sized to support new electric vehicle charging stations, electrical infrastructure upgrades can be provided and/or smart “demand response” charging systems utilized.

Technology like a Smart Charge Manager station can be used with charging stations. This system monitors the building’s overall load, loads of all EV charging stations, charge status of all EV’s, time duration for how long each electric vehicle will be parked (user input required) and whether a priority charge premium option has been selected.  The system prioritizes and gives available electrical capacity to charge the vehicles with the highest demand first (i.e. short time duration & greatest charge required) and vehicles with the lowest demand last (i.e. long time duration & lowest charge required), until all electric vehicles are charged or until a new electric vehicle requiring charging is connected into the system.  The system automatically balances the available electrical capacity to charge the vehicles with the load on the whole building to ensure that the existing building electrical capacity and infrastructure is not overloaded.  The system can send out text alerts to notify electric vehicle drivers of the charge status, so that they can leave and free-up the charging station for another electric vehicle needing charging.

Other Options for Electric Vehicles

For those looking for a bit of extra runtime reassurance that they don’t get stranded on the open road, range extenders or towable gas generators can be used, and function as the equivalent of a “can of gas” to get you to the nearest place with fuel or plug-in to charge.  Another fairly common electric vehicle option, is a plug-in hybrid vehicle.  These electric vehicles are equipped with an internal generator which is used to charge the battery only after the battery capacity has run down.  Plug-in hybrids rely on the battery to handle everything from locking the doors to driving the wheels.  Whereas, standard hybrids, such as the Toyota Prius, are equipped with a gas engine to normally charge its battery and run on battery power at slow speeds.

An electric vehicle might be a good fit for you if your work or destination is only about 25 miles away, electric costs are relatively low, current access to charging stations is convenient, and the range on your battery is a minimum of 60 miles. If you live in an environment where temperatures often fall below freezing, need all the power you can get at a moment’s notice, or the thought of waiting 20-minutes to partially fuel-up using Level 3 or 4 charging still seems too long, then it might be a better and safer choice in today’s market to get a plug-in hybrid electric vehicle (PHEV) or a hybrid vehicle (gas-electric).

Until faster Level 3 charging “DC Fast Charging” or Level 4 Tesla charging stations, which can provide greater miles of charge in a shorter time frame, become more readily available, more Level 1 and Level 2 charging stations located close enough together will be needed to help keep up with the growing number of electric vehicles coming on to the roads. Now is the time to address the electrical infrastructure needed to support this future!

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