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Comment by jscott0918 | Hacker News Reader

I tried to reply to another comment that was since deleted. It said something along the lines of: >I don't get why Tesla would kill their battery-swapping while they are tackling other Hard Problems.

The practicality of battery swapping decreases exponentially as size and weight scale. The cost of building a battery swapping network for western-car-sized battery systems, even once solving the engineering elements (which are manageable), are likely a non-starter. Especially if the other principle technology rival is fast-charging stations.

How much added convenience is required to justify huge mechanical systems with many wear components and large maintenance costs over replacing a few charging cables every X months? Lots.

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I suspect that battery hot-swapping will be practical for electric trucks. Charging them is really slow unless you use a dozen of cables. Parked time costs real money for them. Normal trucks unload, reload, and go back to the highway pretty soon, often with a different driver at the wheel.

Truck yards usually already have equipment for heavy lifting, and the batteries need not be tailored to the car aesthetics and space constraints. Also, a narrower industry has a better chance to come up with a common standard.

Tom Scott did a video[1] on this that tackles the problem of electric trucks in a different way. Instead of charging somewhere or swapping out a battery, what if we charged them while they were in a specific lane of a highway.

[1] https://youtu.be/_3P_S7pL7Yg

I'm wondering how well that will scale if all/most of the trucks become electric. I would think the friction would create issues from both heat and mechanical wear.

Also it's normal with trucks to have a bunch of stuff kind of bolted on the bottom eg https://media.istockphoto.com/photos/fuel-tanker-truck-pictu...

I think the trick is not to swap the whole battery

Instead design in a space for a secondary battery, maybe 40% the capacity of the main battery. Make those standard and swap-able.

Now, you can use the car as ordinary in either the one-battery or two-battery mode, with the 1B config being more nimble handling with less range, and the 2B config more range. In any case, you can then enjoy rapid-swap of the standard 2nd battery, or maybe just rent one for a long trip.

This also helps the automakers keep their proprietary designs on the main battery for differentiation. The 2nd battery could go in the extra trunk space or something...

But if you are talking about faster partial-capacity refills during road trip stops, we already have that.

Current batteries charge way faster from 0-50% than 50-100%. The curve really starts to fall off above 80%.

I usually try to plan my stops so that I’m arriving with 5-10% and charging to 60-65%. With 250kW chargers that results in a ~15min charging stop.

I don’t think the costs of development, impact to vehicle design, and infrastructure would make sense for swaps just to replace what is already a 15min charge.

True, the differential will reduce as we get even higher-amperage chargers and batteries w/higher C ratings.

Yet still, being able to get 40% in 3 minutes is still better. I'd also see little reason that a properly configured trunk couldn't hold a pair of 40% battery units. Kind of like carrying jerry-cans on the back of a rover, except you can just plug them in...

Jerry-cans don't weight 400lb

I suspect that Tesla battery swaps were never a serious endeavor meant to be rolled out, and were instead by design limited to one location merely to be used as a massively profitable tax credit scheme: https://www.forbes.com/sites/greatspeculations/2014/12/30/te...

Doing battery swaps on such vehicles would be incredibly difficult (least of all from an engineering perspective), and my suspicion that it was more subsidy scam than genuine attempt is based on other factors.

The batteri should go in a trailer. Swap the trailer. The car itself could be smaller. Luggage could go on the trailer.

Would make swapping easy but reversing with a trailer is not easy.

Self driving trailer shouldn't be difficult.

Trailers are non-starters for most vehicles.

Better to bring the batteries to charge the cars when they need it: https://www.sparkcharge.io/

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