[bluGill]

> I don't think swappable battery stations would be useful, since batteries are damaged by deep-discharging them, and swap-stations would end up with too many damaged batteries that way.

That depends - just design a tamper evident battery that contains enough electronics so that when you swap it you pay for not just the power to recharge it, but also the damage you did by using it. So long as the fees are upfront and the devices using it will give me plenty of notice before expensive damage happens I'll be find paying for it.

If your swapable battery is just a bunch of batteries you have the risks you state. However it isn't that expensive to ensure that doesn't happen.

[branchly2]

Could work, though I think it would add operational complexity ("hey, I paid to swap in good batteries, but these barely held a charge!").

I wonder if it's possible to have a battery go into a low-current mode when it gets down to $n percent charge ("Warning: time to recharge or swap! You have $x Amp-hours left! Going into econ mode."), then disconnect itself completely when down to $m (where $m < $n, and going lower than $m would significantly affect the life of the battery).

[bluGill]

> Could work, though I think it would add operational complexity ("hey, I paid to swap in good batteries, but these barely held a charge!").

That is part of the business model: the batteries know how much charge they can take, so when one no longer has full capacity you sell it for less. Someone needs to work out what the price levels are so that people don't feel cheated, that is tricky math, but I think we know enough about battery life cycle (over different usage) to come up with something. It will probably be a multi-level thing, a "new battery" will be slightly more than a "slightly used" one, and have a longer safe range before they charge you abuse fees. A "new battery" that is never abused will after so many uses without abuse degrade to "slightly used", the users of it as "new" will pay for the normal wear and tear. If you are not trading in every time the battery needs charging you just pay a small monthly rental fee - if you never abuse your battery when it wears out you can trade in a "no longer usable battery" for a "new one" for just the normal trade in fee. If you abuse the battery you just pay for the actual costs that your abuse did to the battery.

It could work, the real trick isn't the technology (that is a simple computer watching the recharge and discharge rates). Even the business model isn't that complex (though the math is tricky). the hard part is convincing everyone to use your standard form factor for batteries. If every different car has a different battery in some way this will not work. It is only when you have one (or a few) models of battery that everyone has that this can work. There are only 3 grades of gasoline at the gas pump - if your engine would be fine on 60 octane gasoline (like my antique tractor) you just have pay for the more expensive 87 octane anyway. If your engine needs 100 octane (some race cars) - too bad you have to buy your own drum. The same way you need to ensure there is a one size fits all battery. (if you want more having two is an option)