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Comment by mchusma | Hacker News Reader

I agree I don’t like having both engines, more to fail. BUT I could see a world where you basically have basically an EV with a smaller battery pack (150 mile range) and basically a swappable $300 generator. I saw swappable so that if anything goes wrong they just swap it for $300, and credit you back async any recovery value. Just electricity generation from it, for rare needs of longer range. I think in theory, it could be a good way to get a cheaper EV supporting rare bursts of range and low maintenance cost.

But I’m not even sure regulators would allow such a design. Even then I’m not sure it’s worth it.

But I am totally done with ICE car maintenance. I want nothing to do with it anymore.

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A cheap diesel/gasoline generator might do like 5kW, which is enough for overnight charging but not for range extension or powering the wheels. There were several pretty good range extended EVs (plugin hybrid with larger battery and smaller engine), like the Volt and BMW i3, those had small engines that mainly acted as generators for the battery, but with enough horsepower to at least keep you rolling on the highway. A $300 modular generator ain't quite gonna cut it.

I believe there's also a bunch of Chinese vehicles with similar design, entirely electric drivetrain with gas generators for range extension. Most of these will need to kick in before the battery is empty so that there's some stored energy buffer available for acceleration.

To put it in perspective why a 5kWh generator isn't a range extender: my lightening has a range of 331 miles and 135kWh battery. If we assume a spherical cow (60mph, and I get every single one of those 331 miles), the truck buns through the battery in 5.5 hours, which equates to 24.5kWh to keep up.

In actuality, at highway speeds I'll burn through 80% of the battery in 3 hours which equals a run rate of 36kWh. If we ran a 5kWh generator the whole time and assume perfect charging efficiency, it'd extend the time to charge by 28 minutes.

I think you mean kw. The kWh rating is basically just how big the gas tank is.

Technically correct for the rating of the generator output capacity, I was just meeting OP where they were at and they used kwh as a unit for the generator. At the end of the day, that nuance isn't all that important

Using the right units is definitely important. I don't know why we've just decided they don't matter in this regard.

that's kind of like saying you have a 500 horsepower gas tank, or a 10 gallon engine, though.

My Chevrolet Bolt actually shows me the real-time kW draw from the high voltage battery and, while it's highly dependent on driving conditions, it seems to require around 12-15 kW to maintain 60 MPH on a flat dry road using cruise control and with the climate control turned off. It's not the most efficient model on the market, but it's also far from the least; as you noted your F-150 would need significantly more energy under the same conditions.

The lightning is ridiculous, it weight 70% more than your bolt and is huge.

My partner and I honestly bought it to be a whole house backup battery. My regions get ice storms and we have hundreds of gallons of aquariums we'd need to keep powered through a long duration power outage. 135 kwh of battery storage cost more than the 135kwh battery truck, so we got a whole house battery backup system with wheels and cruise control. It can backstop 80 amps for 3 days.

If it were me I'd just get a whole house generator in that situation, seems like it would be a lot less than the truck with batteries or the batteries. The bonuses are I wouldn't need to replace an expensive truck with another expensive truck in the future if I didn't want to. 3 days is impressive, but I had an ice storm leave my family without power for 3 weeks once.

It's pretty strange that 135kwh of stationary batteries are more expensive than 135kwh with a truck attached, seems like some one must be running a screw job on the storage batteries.

Regulations!

We've had pretty poor experiences with generators in the past. A whole house generator is very expensive, especially with a transfer switch. Without a transfer switch you have to run the generator outside and route power inside through a window left ajar, which is not great when the ice storm has happened. The truck is parked in an insulated garage and is easy to route power from.

3 days is impressive if you're pulling maximum you can from the truck, if you pull anything less than that your time is greater. Our aquariums do not require all 80 amps. Max length power outage for us has been a week and the truck will easily last that long.

And totally agree about the cost of battery power banks. This was a few years ago, so things might be different now.

You can't drive the truck during that week? So you need to keep a spare car for the time your battery bank isn't mobile?

Rather, for all the other time when the power is working, you can use your generator for transportation!

I don't know about you, but I'm not driving very much during or after an ice storm.

Besides, the aquariums are fine without power for an hour or three, so technically I could if needed.

For what it's worth you get fairly similar results if you assume an efficiency for a ICE engine (25-40% depending on a lot of things) and work backwards from the energy density of the fuel and the milage you achieve over a trip.

But charging at the service station will take 20 minutes after a 3 hour drive which seems reasonable

We did a 12 hour driving trip just recently. Did 15-20 minute breaks for charging about every 2 hours. Perfect timing to get out, use the bathroom, get a new beverage and get going. Barely felt like we were stopping to charge anywhere except when walking to the bathroom since chargers tend to be on the edges of a parking lot instead of near the entrance.

As a bonus, Ford pushed out an update last year that allowed the truck to charge at 185kws for the first 15 minutes or so of a charge before things heat up, so we took full advantage of it. By the time the charge rate was slowing down we were unplugging to go.

> for rare needs of longer range.

Hmm. Supposing we need a 6 hour drive at 20 kWh per hour (eschewing specific speed/distance figures), and a generous "smaller battery pack" can provide 3 hours (60 kWh). Then the generator must supply the missing 60 kWh during the 6 hour interval, i.e. a 10 kW generator.

Google says those cost from 1k to 5k USD, and they seem rather beefy.

(Just doing the math out of curiosity, otherwise agree with you.)

Yeah... My 7kwh generator is the size of a large wheelbarrow and weighs a good 250 lbs.

Not to mention, loud as all get out at that size.

It also needs a decent amount of maintenance to keep it running (or it needs to run frequently).

Personally... Ev with a swappable battery seems like a much better solution.

The only reason this even sorta makes sense right now is that we're in a really weird transition period where gas is available everywhere and it's still hard to find batteries/chargers.

This isn't a tech problem, it's an infrastructure problem. It should be treated that way.

> swappable $300 generator

It's never that simple, but it could be. Modular standard parts that could be installed on a standard chassis design would be great. So have a small generator or an additional battery, maybe even a fuel cell. Probably never happen but it would be the nirvana of car design. Standardization would drive scale and it could work really well. That approach did wonders for the PC industry.

Why not towable gas generator trailers that you can rent for long trips.

Hook it on, plug the connector up and attach your license plate to the back (or use eink).

Years ago I saw some one who had sawed off the back end of a late 1980s Chevy cavalier (or similar) and turned it into a portable generator trailer for his EV. This was so long ago it was probably an EV conversion of some kind.

There used to be a really classic old website called Mr. Sharkey (you can see some of it on archive.org). He was into a number of different weird and wonderful hobbies. One of them was a VW Rabbit powered by something like a 24hp DC motor and lead acid batteries.

One of the most interesting projects he did was to build a trailer from the front clip of a similar VW Rabbit, engine and transmission etc. He then used this trailer in a pusher configuration to take the electric VW Rabbit on extended trips. The engine was controlled by a hand throttle in the car. Apparently the handling was surprisingly acceptable in this configuration.

Edit - Found the link:

https://web.archive.org/web/20121105135914/http://www.mrshar...

Alternatively, put a battery in that trailer. See for example https://far-a-day.com/en: “Like an external phone battery, but for your car!”

You might be interested in https://en.wikipedia.org/wiki/Extended-range_electric_vehicl...

It's not exactly what you're describing, but I think it will become more common as battery technology growth slows down.

I’m not sure why you’d offer a drop in option if you can just build it into the car. Extended-range electric vehicle (EREV) / Range Extender Electric Vehicle (REEV) do exist on the market already.

A more practical solution is to just rent out a small generator on a trailer.

Unless I’ve completely misunderstood what you’re getting at.

The bmw i3 range extender engine only generates 19kw of electricity. It doesn't allow you to "fill up and drive anywhere" like a car. It is more like a bigger battery.

I think the solution is actually what we have now - high-power dc fast chargers spread around the country.

Basically a modular trunk add-on, with an air and exhaust pipe?

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