[SamBam]

Certainly no one should expect to be able to swap the main batteries that are embedded into the chassis of the car. The total weight of the batteries in a Tesla are around 1200 lbs.

But it seems like there could be a hot-swappable portion of the battery, kind of like a separate "reserve tank" (although it wouldn't actually be reserved).

Some back of the envelope math says that if 1200 lb battery gets you 250 miles, a 200 lb hot-swap battery would get you 40 miles. Possibly enough to get to your next destination.

[usefulcat]

> a 200 lb hot-swap battery would get you 40 miles.

According to one report, for a Tesla Model 3, a supercharger can add ~100 miles of range in ~10 minutes. It's hard to see how any improvement over that could possibly justify the immense additional complexity of physical battery swapping for only 40 additional miles of range.

https://insideevs.com/news/506520/tesla-model-3-supercharger...

[TeMPOraL]

Does the Supercharger network come with a fleet of drones that can autonomously repair a charger in the middle of nowhere, that broke down one late evening of a particularly snowy winter Sunday?

That said, it's probably a UX problem. Once EVs stop competing on range so much, it'll make sense to just designate the last 10% of battery as "reserve" and not count it in the battery level indicator.

[WorldMaker]

Somehow gas pumps get repaired/maintained in the "middle of nowhere" today. Eventually the economic incentives will align that that the charger networks get maintained no matter where they are.

Arguably it should be far easier to get those economic incentives aligned as chargers are far simpler mechanically (they are just plug sockets with weird over-engineered male adapters) and most of what breaks on them is either vandalism or a small subset of existing problems of gas pumps: credit card reader malfunctions, display/screen problems, internet connectivity issues for account management/credit card transactions. (All the human UX points of contact.)

> Once EVs stop competing on range so much, it'll make sense to just designate the last 10% of battery as "reserve" and not count it in the battery level indicator.

Most already do (even while still competing for range) because it's a battery maintenance requirement. Li-Ion cells generally don't like being 100% full, especially not for long periods of time, and sometimes have a preferred "directionality" (ie, a cell should only be charging until it hits 100% and then you can draw from it and vice versa once you start drawing from the cell you should keep doing so until it hits 0%) so battery controllers already have to do a bunch of math to keep a "reserve" so that they don't violate "directionality" (you always want cells in the "charging" direction available even while driving for regenerative braking storage, for instance) and don't generally hit 100% charge for long rest periods, but instead 95% or so.

[usefulcat]

I thought we were comparing fast charging to battery swapping. Surely a machine that physically swaps out a battery is going to be significantly larger and more complex than a supercharger, and therefore also much more likely to break down..

[nickik]

No but there are always multiple supercharges at each station.

> it'll make sense to just designate the last 10% of battery as "reserve" and not count it in the battery level indicator.

Very questionable? Why would you do that?

We don't do that for gas cars either.

[bananasbandanas]

Every ICE car I've ever driven did exactly that with the 'reserve' where the needle is already at (or below) the zero line but you still get about 50 km of range.

[SamBam]

I've been wondering about that with the cars with digital displays, particularly the ones that report your estimated remaining miles.

I once, embarrassingly, found myself on the highway with an empty tank of gas and 20 miles to the next gas station. I watched the estimated miles remaining indicator tick down mile after mile, ticking precisely my passage. At 3 miles estimated remaining, I pulled over because there was a very wide safe shoulder, and I didn't want to putter out in a less-safe spot.

I don't want to try the experiment of letting it tick down to zero and seeing if I still have 10 miles or so left.

[TeMPOraL]

Yup, exactly that.

I think the use cases for field-swapping a (part of the) battery pack are the same as for carrying extra fuel canisters with you, which I can only speculate about, because I've never been in such situation with an ICE car.

[vbezhenar]

What about small generator and a canister of gasoline?

[robin_reala]

That’s what BMW did with their i3 REX models: a scooter engine and a tiny tank, hooked up to the electrical system. Turns out though that the extra weight impacted the performance without adding much in the way of range to the point that it wasn’t really worth it.

[rapjr9]

A 2000W inverter generator could give a Chevy Bolt an extra 14 miles of range after 3 hours of charging. A 240V generator could shorten that time or lengthen the range but would also be larger and take up more room in the car. Carrying gasoline in the back of your car all the time in case you run out of battery is somewhat dangerous. The generator means less cargo space as well. For a long trip to the middle of nowhere it may make sense to carry a generator and some gas. For a trip into town it may not.