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Comment by bwhite | Hacker News Reader

You're not the first person with this idea: http://www.wired.com/autopia/2009/05/better-place/

To some extent there is a standards problem: there is not a common battery pack (like there is a gas tank fill point). But even if there were, the batteries would continue to run down after delivery (unless supplied with a non-trivial amount of power). And the space required to physically store these batteries would occupy a lot of volume. After all, gasoline/diesel is far more energy-dense than modern batteries.

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But even if there were, the batteries would continue to run down after delivery (unless supplied with a non-trivial amount of power).

My thinking is that they would be kept on trickle charge at the gas station after delivery. That wouldn't take a huge amount of power. The actual recharging process would happen at a depot that has high power connectivity to the grid with low distribution losses.

I suspect it would be more efficient to do that and have the charged batteries trucked to the service stations, than it would be to have each service station do their own primary recharging. Especially since, as you say, the service station owners aren't going to want to devote a huge amount of space to battery inventory.

I'm vaguely aware of Better Place but they certainly don't get Tesla's mindshare (good, bad, or otherwise.)

Lithium-ion batteries are supposed to be pretty good as resisting self-discharge, losing only .3-.5% per day (or around 10% per month). The Tesla S has the 60 kWh or 85 kWh battery, so replacing around half a percent of that each day is 300-425 Wh. That's not much at all! If the battery replacement machines are simple and foolproof, perhaps home delivery of batteries and a small trickle charger could be a competitive model to full-blown home chargers?

Storing the batteries at the station will require much more volume than the analogous amount of gas/diesel. And a dumb tank beats a smart battery charger with software and EEPROMs if your concern is resiliency. Some EV problems are pretty clearly chicken/egg adoption problems. But there are some real infrastructure problems, too, and other changes may bear far more fruit towards the goal of more efficient energy exploitation.

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