How useful is the battery warranty, really?

Swappable batteries have been tried, the main company pushing it went bust. NIO are now trying it again. The main concerns are battery ownership, it doesn't make sense to own a battery if you are going to swap it when it needs charging. People generally don't won't a battery rental agreement on their vehicle that covers the battery, one car payment is enough that goes down to zero when the car is fully paid. There were examples of Renault Zoe's that were very cheap but wouldn't sell because of a battery lease, your car without a lease was effectively worthless.

Then there's what problem is a battery swap trying to solve? If it's the charging en-route anyone who's used post 2020 EV for more than a month understands that en-route charging is nowhere near the big deal that it's made out to be by people who's opinion of EVs were formed by watching Top Gear drive a Nissan Leaf in 2011. If it's the battery longevity, we're again facing an entirely different beast from those early examples.

Battery life is primarily a function of charging cycles. NMC type batteries will last 1,000 cycles, LFP one's 3,000. A 2011 Leaf with its 22kWh usable battery should need a battery replacement by around 125,000km, the current Leaf with its 59kWh usable battery should need a battery replacement by 340,000km. A lot of cars have moved to LFP, a RWD Model Y with a usable 57.5kWh should last around 1,000,000km before needing a replacement due to degradation.

If battery swapping isn't needed for degradation reasons, doesn't make much difference for on route charging, and comes with an expensive ownership model, then the only benefit you've identified is that it will make it easier to service in the event of a non-warranty manufacturing failure. We haven't standardised any other major vehicle component for this reason so I'm not sure why a vehicle battery should be treated the same way. I'd much rather see regulation around access to manufacturer diagnostic tools and a requirement for cell level serviceability than an attempt to standardise on a battery format to allow very rare swaps.

Good news, that's what's been happening since the first electric cars hit roads in the 1830's. The last 15 years have seen huge improvements in volumetric density, gravimetric density, power density all while lowering the cost of production.

You seem like someone who's done a detailed analysis what's the magic tipping point when you think it all comes together?

Ok that's cool, so we've solved degradation using suitably sized LFP batteries with their 3,000 cycles. Let's move on to charging time, what C rate do you think is an acceptable level to meet your definition of better and smaller?

You've said you want to see batteries get smaller and better, that's not going to happen on cars that are 8 years old and driving around. So I can only assume that you want to see new cars come with batteries that are smaller and better. We've already covered your arbitrary better standard for degradation is solved by using LFP batteries. It would be somewhat easier if you could just articulate what you think better and smaller means, but I'm happy to work through the problem as it's not often I get to discuss the topic with an expert such as yourself.

Now we're working on better charge rates, so back to the C rate, what C rate do you think is acceptable for a battery?

You want a battery that isn't capable of charging? I'm beginning to think I might be wrong in my assessment that you're an expert in the field and there's any value in your statement that batteries need to get better.