Hacker News Reader

Comment by NickM | Hacker News Reader

It was abandoned because fast charging stations keep improving, and are much simpler and cheaper to operate than battery swap stations. It's already at the point where you can take a 400-500 mile road trip in a Model 3 with maybe a single twenty minute charging stop, which is just not that much extra time, and most people like to take a short break every few hours anyway.

I suspect Tesla knew this would probably happen, but IIRC there was a rule for a while with the California ZEV credit program where manufacturers qualified for extra credits if a vehicle could be "refueled" in under five minutes. Tesla set up a single swapping station to prove it could be done and therefore qualify for the extra credits, but it was always kind of inconvenient and expensive and very few people actually used it.

View on HN

I’d still like to be able to tow a battery behind me for extended trips.

I don’t know how running the AC impacts range, I would like to know. Places with extreme weather and major population centers can make an otherwise short drive really taxing on resources through ac use or just being stuck in place for extended periods of time. Like how peak LV traffic can turn a 15 min drive into a 50 minute drive in 120f+ heat.

Tow-able batteries would make wide use cases like apartments more viable too.

Edit-typo

That seems like a fantastic idea. This way, the car's internal battery can be smaller and lighter for day-to-day use (and therefore more efficient), and whenever longer range is needed you can just rent a fully-charged tow-a-battery, which you can swap out like propane tanks, or recharge yourself at home. These tow-a-batteries would work with any electric car with standard secure hook-ups.

Since these batteries would be rather expensive, I imagine that you would have to pay a refundable deposit to the tow-a-battery network (Shell, Esso, etc.) that covers the full cost of the tow-a-battery in order to rent one.

The biggest down-side is that a rear-end crash could be rather dangerous. I don't see a way around that without making the tow-a-battery a vehicle in itself.

by the time you've added enough protection (ie, extra mass and drag) to the towed battery, it seems like you would be pretty deep into diminishing returns. a large amount of the extra energy would be spent on moving the trailer itself.

Not really. Yes batteries add lots of weight. But electric motors have lots of torque and are known to climb hills easily. Like how Tesla’s forthcoming truck can tow up to 14000 pounds. I’m not doing the calculus, but I suspect the power characteristics of electric motors more than make up for a towable battery.

Edit-here’s an article about a company doing this

https://electrek.co/2020/02/19/french-startup-proposes-batte...

energy, not power. I'm sure the motors have enough torque to tow the battery, what I'm doubting is how efficiently that extra battery capacity gets converted to range.

as an aside, the cybertruck is (probably) pretty bad at towing. see this video for an interesting argument: https://www.youtube.com/watch?v=S4W-P5aCWJs

Very slow video. Wish it were transcripted.

It also allows for faster retrofitting of old vehicles with new battery tech.

It does sound like a very intriguing idea, and one that I believe requires some research.

However, in practice I think this would be equivilent to towing a small tanker trailer full of chemicals or gasoline. It would require plaques indicating the contents, special insurance, and all kinds of BS at the RMV. Imaging if one decoupled on the highway and drove into oncoming traffic at 60mph? It would essentially be a rolling bomb. This happens quite often with camper trailers.

I think engineers would need to emphasize redundancy, failsafe measures, and automated attachment/detachment capability that does not require human interaction to safely accomplish. Then you will convince CA that it doesn't need a ream of paperwork to register and then the rest of the country will adopt it.

So here’s a company doing it for fleet vehicles in China. Granted, it’s not a guarantee it can get through the US regulatory system, but there are definitely more dangerous factors on the road.

Personally I see this as completely new tech from the ICE. That means it really ought to open up new usage and user experiences than the outgoing tech. And those changes should be perceived as better in some way to really take off.

Edit-forgot the link: https://electrek.co/2020/05/06/mobile-ev-chargers-and-vans-g...

Towing would annoying but dropping a block into the Cybertruck bed or the Y back cargo area would be pretty neat.

Most drivers aren't competent to tow a trailer, especially not at high speed or reversing.

Most apartment sized AC units top out at a few kW - that's the peak power, just maintaining the already cooled apartment is going to be consuming much less power.

A car cruising at highway speed is lconsuming something on order of 10x as much power. Given how much smaller cars are than apartments, it's an even greater difference.

So to answer your question: not much. Heating in cold weather is much worse on range, as it's not just the cabin but also the battery that needs to be maintained at an adequate operational temperature.

A car with a 40 mile range would be cheaper to buy, and a lot lighter so also more efficient. You could swap in a 400 mile battery when you actually need it.

The problem I have with the 40 mile range is that is highly dependent on

1. temperature. Extreme cold lowers range 2. topography. Inclines can drain a battery quickly. Declines can add range. 3. driving style. Do you have a lead foot? 4. Driving type. Are you on a highway?

You're nitpicking here. 60 mile range. 100 mile range. Whatever customer needs daily is far different from their outlier use cases. Most people with home/work charging never go below 40 miles from full.

fair enough. It is an innovative idea.

I see, that actually makes sense. To bad most affordable cars actually operate in much lower ranges.

Reply on news.ycombinator.com