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Setting: It's after the apocalypse. No zombies or major nuclear fallout, just 99.9% of people were killed for some reason (superplague, whatever). During the final days of society, massive looting and widespread major panic was going on. No governments are left that have any real reach. Location in North America or Europe. As time passes, survivors need to figure out how to transition from looting and scavenging food to subsistence farming as gasoline and canned foods go bad. Additionally, there is a bit of "Mad Max"-ing going on with bands of raiders who concentrate on stealing from others rather than scavenging themselves--it's a hostile world.

The Goal: Seeing that gasoline driven vehicles will become unusable as soon as gasoline goes bad (even with stabilizers) and diesel is a limited resource, a survivor (or group) decide that they're going to go electric for all their post-apocalyptic transport needs. They reason that an electric car, specifically ones from the current Tesla lineup (no cybertruck):

  • Require electricity which can be easily manufactured by wind, water, or solar power unlike fuel which is a limited resource
  • Are quiet which can be an advantage when hiding from people who would be hostile.
  • Have high torque and towing capacity due to the nature of electric motors

The questions:

  • How long after being abandoned could one get in and drive an EV assuming it is parked in a garage and charged?
  • How feasible would it be for a group of survivors to keep an EV charged for scavenging purposes?
  • How long would an EV last before there's a critical failure/a problem that can't be fixed?
  • Would it be possible to extend the range of an EV by charging it during the drive (eg. with batteries, a generator, or transported solar panels)?
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    $\begingroup$ Modern cars of any type only work well on prepared, clean surfaces. They don't handle off-road well, they don't handle potholes and flooding and ice/snow and collapsed bridges and raider barricades, etc, that will be common obstructions after a few weeks without regular maintenance, policing, and cleaning. Consider a nice solar-powered horse instead. $\endgroup$ – user535733 May 10 at 15:49
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The base Model-3 comes with a 50 kWh battery. To put this into perspective, a high-end car battery found in a conventional combustion engine car have an energy storage of about 1$\frac{1}{3}$ kWh. So unless you have another Tesla battery (and the things are quite heavy) you won't have much in the way of portable electric power.

The standard for solar panels is about 1.5 kWh per day in good conditions. So to charge your car you'd need a lot of solar panels, and this would only work for sunny conditions.

High-end Residential Wind turbines can produce up to 15 kWh per day. This is a bit better than individual solar panels, but they are physically large and you need a lot of space (they need to be spread out so as not to interfere with each other). Again, as with solar panels, you need the right conditions and these good windy conditions are quite rare depending on the location.

Solar panels won't last forever; they can last decades but more often then not they will lose ability to generate their peak power after a few years, which will then keep getting worse over time. Wind turbines are similar in that they can last decades, but mechanical issues can and do occur and they typically lose their peak performance over the scale of years and not the decades they can theoretically last.

Now just because you have enough solar panels and wind turbines to generate enough power, doesn't mean that the battery will charge instantly. You need to store the energy first in batteries. From what I can find (Disclaimer: I don't own a Tesla so I'm relying off of what I can find on the Internet), it may take up around a day or more to charge the 50 kWh battery using 120 V AC. From what I can gather unless you are generating at least 50 amps, the car will take days to charge. You can step voltages up, but you trade off the current you can generate. So unless you have an entire solar farm or an industrial wind turbine with associated energy storage, you likely won't get very far charging your Tesla.

So is it possible; yes. Are there better options, certainly, Diesel systems can be modified quite easily to run well on just about any oil or fuel. They won't be very efficient or clean, but they will run and you can even keep producing the fuel; all you need is a farm.

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  • $\begingroup$ you say "the standard for solar panels is about 1.5 kWh per day in good conditions" this makes no sense, what solar panels is this standard for? what size? I have a simple solar panel kit. it by no means produces 1.5kwh per day. what standard are you talking about? $\endgroup$ – Topcode May 10 at 20:27
  • $\begingroup$ @Topcode From my experience this is the energy per panel unit for roof based solar power kits, and is often advertised as such for peak performance. Of course peak performance does not occur all the time. This is for each panel at 250 W assuming at least 6 hrs of perfect conditions. $\endgroup$ – user110866 May 10 at 21:14
  • $\begingroup$ @Topcode my point is to show the difficulties, even with near perfect conditions, to charge a Tesla with only solar power. $\endgroup$ – user110866 May 10 at 21:16
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Some of the other posters have pointed out the issues with attempting to charge an BEV like a Tesla, but I'll take issue with your other statement about fuel.

IC engines can be recalibrated to run on alternative fuels. If you have access to farmland, you can raise crops like corn or potatoes and use it to create alcohol. Methanol can be brewed up using things like wood chips, and biodiesel can be extracted from plant oils.

https://greenliving.lovetoknow.com/How_to_Make_Ethanol

https://www.fpl.fs.fed.us/documnts/fplgtr/fplgtr12.pdf

https://www.utahbiodieselsupply.com/makeyourownfuel.php

If you are not as conversant with chemistry, you can put together a wood gasifier, similar to the ones used in WWII to convert wood into energetic gasses like carbon monoxide which can be fed into an internal combustion engine as well. The linked plans are from a FEMA project to specifically create a low cost unit capable of being built from scavenged items in a post apocalyptic setting.

Even if you want to stipulate the actual vehicle engines are not going to be usable due to the computer control programs being corrupted or something, these fuels can be used to run small generators which can charge the batteries or run other electrical appliances.

So chemical energy isn't going to go away just because of the apocalypse, and may even be easier to use without regulatory impediments, lots of space and lots of raw materials available (making alcohol in the modern world requires a great deal of regulatory hoop jumping, for example).

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The problem with this scenario is you are assuming that the electrical grid is still up and running. While a mass-die-off would definitely decrease the demand for electricity, the grid itself, and the generators, and so on require maintenance. It doesn't run indefinitely by itself.

A Tesla model S takes FOUR DAYS to charge at 110V (i.e. regular AC), assuming the current 100 kWH battery. With solar cell, it'd probably take MONTHS, depending on the size and efficiency of the solar cells in question. Obviously you don't need to FULLY charge it... But I think I've made my point.

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  • $\begingroup$ Let's assume 300 w/sqm and 20sqm of solar panels. By watts alone, it would take ~16 hours to charge at full sunlight. Water power off a small stream can also easily go into kw output ranges; yes it might take a day or two to charge, but then you'd have several hundreds of miles of range $\endgroup$ – Dragongeek May 10 at 9:45
  • $\begingroup$ I'd say you're a bit too optimistic there. Current technology is more like 100 W/sqm. That's by checking some random "portable" 100W solar panels on Amazon. And that's obviously assuming max sunlight scenario (i.e. Arizona desert) And these solar cells do 12V DC. That doesn't really charge Tesla batteries at 110AC at the minimum... Then you have to include AC inverter losses... It can get a bit messy. $\endgroup$ – Kasey Chang May 10 at 9:55
  • $\begingroup$ regardless, with a roof full, it wouldn't take months, more like days. $\endgroup$ – Dragongeek May 10 at 9:58
  • $\begingroup$ Okay, I'd go weeks instead of months. After all, daylight is limited. But it's gotta be more than 4 days.I'd say 2-3 weeks at the minimum for a full charge. $\endgroup$ – Kasey Chang May 10 at 10:00
  • $\begingroup$ 20 square meters is 4 by 5 meters. A typical car is less than 3 by 2. $\endgroup$ – L.Dutch - Reinstate Monica May 10 at 10:10
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There are a couple of answers here that point out the immediate problem of charging time.

There are other issues you need to keep in mind:

One is how long your Tesla can operate on that charge.

If the Tesla takes days to charge and can only operate under heavy loads for half a day, you aren't going to use that device as a farm tractor. You're going to reserve those high-effort battery charges for things of more significance. Maybe build that chassis into a fire truck, where speed and power matter a great deal and you can (hopefully) afford the downtime between charges.

Two is Tesla to work vehicle adaptation.

How difficult will it be to take a chassis (and the computer controllers) designed for road use in a sedan and retool the entire thing to work with a heavier vehicle? Can the motors in a Tesla handle the extra load if you just try to slap them into the equivalent of a farm tractor or a heavy load truck chassis (dump truck, back hoe, tractor trailer truck, etc.)? Or will the load burn out the motors? I am not an engineer, but I suspect the reconfiguration of the chassis will reduce motor life drastically, at best. And of course, the heavier the work, the shorter the battery life.

Three is battery lifespan

Tesla batteries are based on laptop batteries, but better. In laptops, those batteries begin to hold less charge over time. Laptop vendors will not give more than 1 year warranty on those batteries, because they fade with use. Now, newer batteries tend to withstand this better than they used to. And Tesla's are a few steps up from laptops now. But eventually, those batteries will begin to wear out. They just won't hold a 100% charge at some point, meaning your 6-8 hour run time drifts slowly down eventually, reducing effectiveness even more. Tesla warranties their batteries for 8 years, so I suppose you can go about that long, but past that, your life is going to dramatically fall.

Four is vehicle complexity

Books and basic tools can be found to make working on a typical 1980s-era vehicle possible. But the more advanced a vehicle becomes, the more specialized the tools and skills required to maintain that vehicle. Will your survivors have those skills? How hard will it be to acquire parts and tools to work on those systems? How many different specialized skills will be required to take a Tesla and convert it to heavy workloads? Engineers? Programmers? Electricians? My father was able to adapt a 1940s truck body to fit a 1970s truck frame/engine. He had nothing but self-learning and books for both trucks to make it happen. Modern cars are not that "easy." And all of those highly trained car maintenance folk are taken away from food production, which is a critical thing.

Five is design life

I hinted at this with the batteries, but eventually, even if the batteries fail, something will break. Your car will need things that require factories that require sub-factories that require mineral refineries that require mines. Sure, at first you can scavenge for parts. But at some point you're going to hit a wall where you need parts that either can't be found, can't be extracted, or that have exceeded their "shelf life." You have a few hundred people. They aren't going to be able to get the raw materials, build the refineries and factories, to assemble those parts.

Better alternative

All of the above highlight a great deal of effort required to operate machinery that runs a few hours then sits there, taking up space, for a few days.

Far more efficient plan is:

  1. Use gasoline while it lasts, but immediately begin gathering diesel vehicles and animals.
  2. Use diesel vehicles (with alternative fuels as needed) for as long as they last but continue to gather animals.
  3. Switch to animals. Horses, mules, oxen, etc. are your future.

Gas will expire first but is the most plentiful. So use those vehicles hard and abandon them when they fail. Gather gasoline and immediately stabilize it, but accept that this is very much a temporary solution. Use those vehicles to build your initial compound and to collect diesel vehicles.

Diesel can be renewed via cooking oil, etc. with little in the way of complex works. And they are efficient for heavy work loads. Use those vehicles to complete your compound(s) and to collect more vehicles / materials. But again, know that this is temporary.

Finally, be prepared to fail back to older, easier, technology. Immediately begin collecting horses, mules, and oxen. These creatures are self-building, low maintenance relative to EV, and can be used as food at the end of their design life. Sure, they're not perfect either. But they don't require an entire infrastructure to create, fuel, and maintain over the long term.

Farming is your future. Use what's left from the good old days while you can, but be working towards the long-term, because your survivors are effectively going to be Amish -- in lifestyle, not in religion -- within 2 or 3 generations.

Sure, they can try to gather what they can and hope to not completely backslide. But rather than devote so much effort to supporting such inefficient machines as EVs, much better to be focusing on skills that can be locally supported without requiring entire infrastructures worth of industrialization. Rather than sending half a dozen people to learn mechanics, electrical engineering, and such, send a few to study up on blacksmithing, a few to study farming, and a few to study animal husbandry/veterinary medicine. Those skills will do you more good in the short and long term.

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