Right now, the electric vehicle ownership experience is optimized for the owner who lives in a single-family home. A level 2 home AC charger costs a few hundred dollars, and with a garage or carport, an EV that gets plugged in each night is an EV that starts each day with a 100 percent charged battery pack. Plenty of Ars readers have told us that a 120 V outlet even works for their needs, although perhaps better for Chevy Bolt-sized batteries rather than a Hummer EV.
However, about a third of Americans live in large multifamily developments, often in cities that stand to benefit the most from a switch to electrification. And electrifying the parking lots of existing developments is often easier said than done. Some developments will allow individuals to install their own dedicated charger, and newly built developments may even have planned ahead and put conduits in place already.
For many others, the parking spaces will be owned by the condo association or co-op, complicating the idea of giving each EV driver their own plug. Here, shared solutions make more sense, perhaps starting with one or two shared level 2 chargers as a pilot—often this won’t even require extra work to the electrical panel. Costs are a little higher than for a home level 2 charger—between $7,500–$15,000 per charger, perhaps.
But for larger developments, scaling up level 2 chargers can quickly become prohibitively expensive. Older buildings may well need their electrical infrastructure to be upgraded, and running copper wiring across parking lots starts to add up fast.
Faced with the install costs for a dozen 2 chargers, a battery-buffered DC fast charger starts to look like an attractive alternative. These use an existing electrical feed to trickle-charge a lithium-ion battery pack that can then DC fast-charge an EV, rather than requiring hundreds of kilowatts. Instead of taking 6–10 hours to recharge with AC power, about 30 minutes is usually sufficient to return most EVs to 80 percent state of charge with a DC fast charger.
So, instead what we are doing (after consulting with the utility) is to allow 30 amp chargers, with time-of-use restrictions (overnight, basically). The headroom comes from the improvements in efficiency of just about everything over the last 40 years. Lights are now LED. Appliances draw much less power. That 70 A includes a central HVAC unit, and modern ones draw a lot less power. This allows using the existing infrastructure, and residents who want to install chargers in their spots just have to run a circuit from their meter (in the garage) to their designated spots. 30 A is plenty for overnight charging, and in the future we could revisit if more capacity is needed. It's marginal for owners that have two EVs and drive them a lot, so at some point we'll probably have to upgrade the infrastructure, but this gets us most of the way there.
Battery-buffered may be a good solution in a light duty cycle application, but after my encounter with one of these contraptions this past weekend, I will remain a skeptic until proven otherwise.