Gasoline is largely fungible because it's required by law to be. What can be called gasoline, what additives can (and are required to be) put into it, how much energy it has per liter, etc., are all regulated.

There was a time where gasoline brands mattered, and the gas you got from Esso might have been slightly different than the gas from Sinclair or Hess or whatever, but that was intentionally regulated into irrelevance because the benefit to consumers of a consistent product was more valuable than allowing brands to differentiate themselves.

It took several decades after the widespread adoption of the car (and gasoline as the dominant fuel) for this to happen, and during this time users had to struggle with varying fuels produced from different feedstocks, gumming of engines, dilution of crankcase oil, etc. (This is referred to in period motoring publications as "the Fuel Problem".) The automobile industries and the oil industries basically pointed fingers at each other until the US Bureau of Standards had to step in and mediate on a consistent set of standards that the refiners would produce fuel to, and the engine manufacturers would design their engines against. If this hadn't happened, and the market had been left to sort it out, I suspect you would have ended up having to fill your Ford car only at Sinclair stations, based on some Ford/Sinclair arrangement or whatever.

Unfortunately the 'solution' to the Fuel Problem in the 30s involved the introduction of tetraethyl lead, which mars what would have been a good example of mutually beneficial public-private cooperation and useful regulation.

to an extent that it matters, yeah.

Sure, I put 87 octane in our SUV and 89 in the audi, but yeah for the most part gas is gas, unless something is wrong.

Getting 2 random batteries to have less than 10% variance among them is going to be a lot harder (especially when battery health changes a lot depending on how they are treated. Users running them to near empty in cold weather is going to shorten the life a lot faster than the guy who only runs it to 50% before swapping out every time), and I have a feeling that the amount of "problem" batteries will be much higher than the amount of times i've ever had "problem gas" (which is basically 0 times so far).

Side note: is that a typo or do you really have 87 octane gasoline in the USA? Because it's 95 and 98 in the EU.

yes, but we use a different method of measuring than you do.

IIRC ours is the average of 2 different methods (it normally shows as R+M/2 on our pumps), whereas I believe the EU uses only the one that tends to be a lot higher (RON I think)

Most gas stations around me have 87, 89, and 91, and sometimes 93. I believe your octane numbers will be on average like 6 higher than ours for the same gas.

They're possibly different measures, RON vs MON. The wiki article has more including a photo of an offending US gasoline pump https://en.wikipedia.org/wiki/Octane_rating

I am assuming in a hypothetical battery swap world batteries would be rigorously tested before replacement. How hard do you think it would be (sincerely)? For the gasoline analogy, there are lots of ways to achieve an octane rating but I suspect most people only use the "do I hear engine knock" test. Similarly, I would be fine of a guarantee of if I have 300 mi of electric range (whether it's 300, 310, or 320) under normal driving conditions for a battery swap, as a trade off for convenience.

I really think it would be a lot harder than testing gasoline.

For starters, with gas and other things like it, there is a supply chain which is pretty tight. If one supplier starts giving bad gas, you can blacklist them and move on. With batteries you'd have to test them after every single use, because you don't know what the last user has done to them.

Then they need to be physically inspected, because a puncture or deep gouge or crack or something could cause big issues.

Then their actual capacity needs to be tested some how. I'll admit that I've been outside of the battery ecosystem for a while, but years ago it wasn't all that easy to "spot check" a random battery to find it's health and capacity. Most devices would gain that knowledge about a battery over a few charge cycles. You need to make sure you know it off the bat, and you can't be wrong or I'll lose faith in the company and the tech.

Then throw in the complication of different sizes, different shapes, different technologies, different requirements (this isn't just the "gas" part of fuel, it's also the "gas tank", so one size will never fit all), and now you are maintaining huge banks of different kinds of batteries all while charging them to the right amount without degrading them, and checking that users didn't run them in below freezing to almost 0 percent which would reduce the lifetime and aren't damaging them in any way which would be very unsafe.

In an ideal world, it sounds like a great idea, but I just don't trust that it can be pulled off without making the user's life worse than if they didn't do it.

A couple of things: when I think about it, I implicitly think about it as a vendor specific thing. Like Tesla supercharger stations. Agree that battery standards across makers likely impossible. Second, I think the major upside is removing a large potential liability from each vehicle - as hybrid vehicles are entering "old used car" ages/mileages, all your points about assessing the health of the battery apply to 2ary buyers and ability for people to monetize their old vehicles.

Bringing it back around to the topic, I don't know that we can wait on solid state and this represents a work around while smarter people that I can figure that out.

If you investigate the way gasoline is distributed in the US you will see that it is extremely fungible.

Sure, but my point is that you have gasoline being produced by many companies and production facilities, from many different/blended inputs (heavy oil with low gravity, NGLs, ethanol mixture, et al), and with proprietary additions.

There's no reason that batteries can't be checked that the meet spec before they are replaced in your car in the same way.

I'd be surprised if each battery couldn't come with a little computer that tracks charge times, cycles and power output over time. It would make it trivial to monitor whether or not a battery is currently serviceable (or whether it will expire prematurely).

For EV fleets we used to only be able to do this per vehicle (not by battery) while the vehicle was home and charging, by shipping the fleet battery metrics to a central aggregator. But that is overkill for consumer vehicles.

With Tesla, every single cell has a computer chip monitoring its performance on a variety of issues. And the aggregate data for that is all called back to HQ on a regular basis. Tesla knows better than you ever possibly could as to how well each and every cell in your battery packs is doing.