That doesn't really scale. The power grid needs to be reliable, and there needs to be some idea of how much capacity you actually have.

If people simply hook up an unknown number of batteries of unknown capacities in unknown spaces, how can you rely on the resulting power grid? How can you plan extensions?

Not to mention high capacity batteries are huge fire risks, especially worn out high capacity batteries. Can you imagine how much water you'd need to put out a 200 car battery lithium fire? Iw would be truly irresponsible to let scrapyards build makeshift power storage stations like this.

There are plenty of grids with wide deployment of community solar, which are also unknown-capacity, unknown-delivery. They work because in aggregate they are predictable. The demand side of most power grids is the same - you don't need to tell anyone that you want to switch on the oven, but if everyone in the world switched on their oven at the same time, the worlds electricity grid would collapse.

At scale, everything becomes more predictable, because individual failures no longer have much impact.

Battery operators also will configure their systems to make money, so they will in fact have a big incentive to buy power when it's cheap and sell when expensive, so they will form a strong stabilising force. (unlike say solar, where operators don't track the price and just inject whatever power they produce, even if the spot price of electricity might occasionally go negative, and when it is negative, there is unconstrained overproduction)

> There are plenty of grids with wide deployment of community solar, which are also unknown-capacity, unknown-delivery.

There are some important differences. For one, those are using bespoke new batteries, not used car batteries. For another, the battery storage is not concentrated, so much lower risk of fires spreading from battery to battery (which you've ignored).

For a third, if a battery fails, it's most likely going to be the house whose battery has failed that loses power if the grid was at its limit, it won't be a whole neighborhood, nor some industrial plant.

Finally, I would be quite surprised if there is any significant power grid where any industrial consumer would be at a risk of losing power even if all community batteries were to be unplugged from the network (ignoring the effects of a sudden surge, like in the oven example, of course).

Sell a storage system that allows the batteries to be safely and individually stored and integrated. It could estimate the capacity of each battery and house 20 or so. Such a system could probably pay for itself after using it for less than a year. There are certainly going to be guaranteed minimum capacities that such a system could promise, it doesn't need to be perfect. If enough people invest in such power storage systems, you don't need to have a single system work 100% of the time, just like you don't need every wind turbine to work 100% of the time.

You can come work on the problem of opening up the electricity market to small players today: https://www.arcadia.com/careers

Alas, I see no way they'll be successful, because the 'old players' who need disrupting own all the electricity cables and get to set the rules.

Well, our growing revenue seems to suggest otherwise, but I guess we’ll just have to wait and see!