batteries

That means production can be cut in half because batteries last longer, to sustain the same storage levels.

Batteries are usually a lot cheaper than generators, so it might make sense, as you say, to just replace the batteries a few times.

They're usually marketed as marine batteries rather than car batteries.

But we know that utility scale batteries can be much cheaper (I mean these Tesla powerwalls are quite similar to batteries that go into cars, their energy density is very high due to space constraints.

Lead-acid batteries can't be used effectively for energy storage, especially not vanilla car batteries that are optimized for cranking amps but will only last a few cycles of charging and discharging.

Standard lead acid car batteries don't like being discharged below ~50% like others have pointed out.

If X ships a device with exploding batteries manufactured by Y, X is sued by the end customer, not Y.

Is there actually going to be enough lithium to build the many millions (billions?) of kWh of batteries to do this?

Generally, lead-acid batteries will sulfate at low levels of charge, which is a hard-to-reverse reaction.

Although that might be true, battery powered flashlights/torches suffer from the problem of leaky batteries.

Sure, one should check the batteries every year or so, but who really does that?

Philadelphia is the town that boos Santa Claus and throws batteries at baseball players.

And before anyone jumps in and says "lithium batteries self discharge!" Yes, yes they do.

But generally, no matter what sane thing you do to these numbers, halve them, double them (maybe cheaper cars use crappier batteries/engines, maybe they mean light trucks too, etc), it's still "a lot of extra to plan for".

Batteries tend to have a very short lifetime, measured in months to years, and they can typically only be recharged a few hundred times.

Batteries do indeed have orders of magnitude higher energy density per kilogram and per liter, about 400kJ/kg and 1MJ/ℓ, while a bag of sand that has been lifted two meters only stores 20 J/kg and something like 20 J/ℓ.