BMW i3 REx is pretty much exactly as described. It has a 38 hp twin cylinder motorcycle engine which is more than your ideal 20, but even that is known to slowly lose charge while climbing long hills since the engine can't output much power. The engine is not mechanically connected to the wheels.

Interesting oddity of incentives. California's zero emission vehicle rules state that range extended EVs count for more zero emission credit, but to qualify as range extended the gas range can't exceed the battery range. Since i3 had a pretty small battery and BMW didn't want to go to the expense of building a different, smaller tank for the US they shipped the i3 with a software locked portion of the gas tank. You can flash the firmware to unlock the full gas tank (which is still pretty small).

i3 wasn't a huge success. BMW made a bet battery prices would stay extremely high and weight would really matter in an EV. i3 and i8 were experiments to see if they could build cars from carbon fibre re-enforced plastic at scale economically. Spoiler alert: they couldn't. That meant i3 was shockingly expensive to buy and even minor collisions can write the entire car off since even hairline cracks in the CFRP shell can result in catastrophic failure.

Unfortunately for you I don't see any new vehicles being designed to fill that niche. Designing a ground up PHEV is far too expensive, so every manufacturer is just electrifying their existing gas designs and stuffing batteries anywhere they can find a spare bit of space. Since engines give off waste heat for free no one is going to bother making a full heating system just for the plug in version since it would drive the sticker price up on a plug-in even higher (and they are already a tough sell since they get up into full EV range). Combined with the charging network getting better very rapidly and PHEVs are a bit of an investment dead end. They will continue to exist (especially in the EU market), but everyone is putting the absolute barest possible engineering effort into them.

The good news is that this type of car has been around since at least 1900 with the Lohner-Porsche Semper Vivus [1] which had a version with a motor to top up the battery.

The bad news is that they haven't been that popular. You might be able to find a used BMW i3 REx in Australia, but it was discontinued in 2019.

[1] https://en.wikipedia.org/wiki/Lohner%E2%80%93Porsche

Chinese manufacturers are now focusing on long range PHEVs https://carnewschina.com/2023/01/11/2023-changan-uni-k-gasol... https://carnewschina.com/2023/04/18/byd-destroyer-07-phev-de...

That's basically a hybrid vehicle where the engine is not connected to driveshaft. The thing is -- it's more efficient to connect engine directly to the driveshaft when driving at a reasonable speed, as there's no extra conversion of gas to battery charge (generator losses + battery charging losses + battery discharging losses).

> 1. Capable of driving ~100km on a charge, with a fully electric drive train

> 2. A small (~20hp) internal combustion engine + generator able to charge the batteries while driving.

I don't think a 20 hp engine is going to be big enough, unless you're talking a microcar.

PHEVs I'm aware of don't have the battery range you're looking for either. And I don't know what's available in Australia. My PHEV has an 'ev only' mode where it will rarely start the ICE unless you use up the battery, but it's slow to get up to highway speeds without the ICE (it will prompt you when accerator input calls for more than the battery and motor can deliver, and if you floor it, it will start the ICE without you accepting the prompt) and battery range drops sharply at highway speeds anyway. If the battery is charged enough, it already doesn't run the ICE that much at city street speeds, unless you've asked for the heater. In mine, EV only range is about 20 miles, and running in auto after a full charge is likely to use up the battery within 35 miles in auto mode.

This is not a long term solution because we need to entirely stop barfing CO2 into the atmosphere and extract the CO2 we’ve already put there.

FYI they did sell the Volt in Australia as the Holden Volt between 2012 and 2015, they only sold 246 in that whole time though, so not a lot of choice out there on the second hand market.

The closest thing in a new car will probably be the Mazda MX30 R.EV hybrid coming to Australia in 2024, which is primarily electric drivetrain but uses a small petrol rotary engine to charger batteries as a range extender, but that is a very niche vehicle and the rotary engine isn't particularly fuel efficient on petrol use, but it is small and lightweight compared to a piston engine.

Nissans Qashqai and X-Trail hybrids also use a primarily electric drivetrain with the petrol motor only providing power to the electric drivetrain, similar but not quite the same thing as the motor is in use a lot of the time.

A most sensible idea, first one I see in EV context! The US and Australia are very different but for other places in the west I think fully electric driven for 100 km is to much. The combustion engine would grow along with the weight that grows along with the battery weight. Making the engine and fuel tank larger and would make them and the frame heavier which in turn would ask for a larger battery which asks for more hp again and so the circle continues.

The lower limit seems safety which depends on the other clunkers [allowed] on the road. Solar seems a good way to add weight and strengthen the structure.

Another sound idea is to swap the battery or parts of it. The bigger it is the harder that puzzle gets. I want to see swap while moving tech.

Mazda is supposedly making a MX-30 R-EV, which has a extending rotary engine in it. At 74HP though the rotary probably can act as a full-series generator. https://www.caranddriver.com/news/a42485033/mazda-mx-30-r-ev...

I was hoping there'd be a much smaller rotary creatively tucked away somewhere, but this is a fairly conventional car design & there's a big old engine bay with the rotary taking up a bunch of space.

In addition to the BMW there is the Nissan Note e-Power and the Honda Fit/Jazz hybrid -- just off the top of my head. The Note is rated for 800km (500 mi) per tankful, IIRC. I believe the Jazz is no longer sold in AU but there are used imports from Japan, probably.

The thing you want is called a "series hybrid" design.

1. Nissan e-Power: https://carbuzz.com/news/what-is-nissan-e-power-and-why-cant...

This the basic idea behind hydrogen fuel cell cars too, only with a fuel cell instead of an engine. The goal is 100% zero emissions with 100% the functionality of existing cars.

It is also why existing BEVs are almost certainly a fad. After all, why will innovation suddenly stop in transportation, and fundamental ideas like low weight and fast refueling suddenly became irrelevant? All signs point to BEVs being an idea from the mid-2000s, and for whatever reason had become stuck in our brain.

The engine would only need to run at a constant speed/load, etc, so this might be where some alternative engine designs, some very compact, could be effective.

buy a Rivian and put a generator in the bed of it?