[T Ruth]

In my understanding, it depends on the battery chemistry being used, e.g., lead-acid vs. lithium-ion vs. numerous other possibilities. For the chemistries that right now appear the most promising, what shortens battery life is deep-discharge cycles. As I understand it, battery management software regulates the depth of discharge, the recharge rate and other factors to optimize battery life for the performance demanded.

In short, with sophisticated software, the thing can be managed to be profitable.

By the way, I understand that there is a start-up company (not publicly traded) that is developing software to manage the transfer of electricity between vehicles and the grid, as opposed to on-board software which manages only the on-board battery.

[kinoxi]

Where does the initial energy source come from that is sold to the ‘grid’?

[ltc8k6]

Why can’t I just buy a battery pack, or make my own from deep-cycle batteries, add a small fuel efficient generator, and the interface hardware, and make a couple grand a year?

Why pay for the rest of the car if this will be profitable to me?