Typical EV Charging Use Cases for Public Transit Bus Charging

Joseph, Gottlieb, CTO, Tuesday October 12, 2021

Near the “far end” of the medium- and heavy-duty (M/HD) electric vehicle (EV) charging spectrum are public transit buses. These buses tend to be very large, with some of the greatest battery capacities. For instance, the Proterra ZX5 Max transit bus has a maximum gross vehicle weight rating of 43,650 pounds, an operating range of 221-329 miles, and a battery capacity of 675 kWh – well over 4 times the battery capacity of an average school bus. And their average daily energy consumption for most use cases is 80%-90% of their total capacity; recharging one of these vehicles typically requires over 600kWh of energy. Even with a charging window of 7pm to 5am (10 hours; some can be shorter than this), one of these buses would require the input of 60kW per hour. If the charging window is shorter or the bus arrives late at the vehicle yard, it will require in excess of 60kW per hour. And while there are public transit buses that are smaller (and have lower battery capacities) than the Proterra ZX5 Max, even cutting the 675kWh battery capacity by a third still results in a capacity of 450kWh.

For public transit buses, high-power DC fast chargers are the only answer. For instance, using a 125kW DC fast charger like the Rhombus RES-DCVC125-480 could fully charge a Proterra ZX5 Max transit bus in under 5.5 hours, or a bus with a 450kWh capacity in slightly over 3.5 hours. In both of these scenarios and if the route times supported it, two buses could share a single PCS. This approach could significantly reduce charger infrastructure capital costs and deployment costs. This is also a use case where vehicle to grid (V2G) could also make sense, given their battery capacity.

If you are looking for made in the USA high-power DC fast charging systems for those EVs, look to Rhombus Energy Solutions. Our market-leading bi-directional EV charging systems (which are designed from the start for the needs of fleet operators) are designed and built in the USA. Rhombus also excel in the design of high-power smart inverters for next-generation renewable energy and energy storage deployments. Our expertise in energy management system (EMS) software is also embedded in our VectorStat EMS controller and software which is embedded in our EV charging systems and smart inverters. We have built over a thousand V2G-capable high-power, high-reliability chargers and bi-directional smart inverters for a variety of different sizes and classes of EVs.

Find out how we can help you by contacting us at [email protected], or by reading our Vehicle to Grid Solution Brief.