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Are Batteries Really An Option for Fleet EV Power Storage?

(Joseph Gottlieb, CTO, Thursday, May 14, 2020)

Rick’s last blog talked about different energy storage options for electric vehicle (EV) fleet operators, including siting containerized batteries at EV fleet operators’ vehicle yards. But do fleet EV operators really  want to give up significant portions of their vehicle yard for “boxes of batteries”? Let’s look at a hypothetical “real world” example to see if this is really an issue. For our example, we will use a transit bus yard. Assumptions and results:

  • Bus yard has 200 vehicles, 70 of which are electric (35%), with 660 kWh of battery capacity each.
  • The yard has an existing 2MW power feed.
  • The buses return at the end of the 12-hour shift with 90kWh of energy.
  • Charging the 70 buses will require 40MWh of energy (70 x 570kWh).
  • The existing 2MW feed can provide 24MWh of power (12 hours x 2MW), leaving a 16MWh gap.
  • Using battery storage during the day that is 90% efficient would require 17.8MWh of battery storage (16MWh ÷ 90%; we will round to 18MWh).
  • This would require six (6) 40-foot containers of batteries, assuming 3MWh per container.

Since containers can be stacked up, the footprint is equal to 3 container, which would be the same footprint as 3 buses – about 1.5% of the parking spaces in the bus yard. As you can see, the impact to space in the bus yard is not significant.

As a leader in the development and manufacturing of bi-directional, high-power energy systems for both vehicle charging and photovoltaic solar applications, Rhombus is an expert in high-power charging systems for EVs, and especially in the area of vehicle-to-grid (V2G) charging. Find out how we can help you by contacting us at, or by reading our Energy Storage Reference Architecture white paper.

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