Hacking A Hack: Electric Hybrid Geo Metro

[Ben Nelson] turned his electric Geo Metro into a plug-in hybrid. But wait, where’d he get an electric Geo Metro? It seems that we’re one hack behind [Ben], who converted the vehicle to all electric back in 2008 using a forklift motor and some batteries. This time around he’s following the Chevrolet Volt’s example by adding a backup generator. Instead of going with a gasoline power he added a tank of propane and the generator from a Recreational Vehicle. This won’t put out enough juice to drive while the generator is running, but you can use it to extend your traveling range by pulling over for a nap while it tops off the batteries.

54 thoughts on “Hacking A Hack: Electric Hybrid Geo Metro

  1. You can purchase impact resistant propane tanks. I doubt the ones sold with a BBQ grill meet that requirement.

    Also, there are additives in the propane to reduce its volatility and make it ‘smell’ in case of a leak.

    Maybe with some upgrade to the tank and generator this is a viable project for everyday use. But hey, you gotta start somewhere.

  2. Ben is a member of the Milwaukee Makerspace. Anyone who is interested in this type of project or other cool projects and lives in the Milwaukee area should stop by for one of our meetings. We have meetings every Tuesday and Thursday starting at 7pm. We are located at 3073 S. Chase Avenue Building 34 Milwaukee, WI.


  3. The propane tank in the rear is fine. The biggest hazard is actually the top breaking off. It would change the pressure in the cab rather quickly. He could benefit some extra safety by turning it around so the shroud covers the rear so it is harder for this to happen. I have seen those small tanks go off in an open area, they fly around like a torpedo with no navigation system. They don’t go boom like you would think after watching movies. The tank is very thick, go clean one out and see for yourself, There is a better chance of someone hitting the tank and pushing it into the driver, than actually rupturing the side of the tank.

  4. BBC Top Gear did pretty much exactly this while messing around with a hacked-up electric vehicle.

    I’m assuming the exhaust vents directly outside? I suspect with a more efficient generator you could get more range out of it.

    1. Yeah, I’d prefer to have the generator and propane tank outside the passenger cabin, such as in the back of a pickup, or seal off the rear portion of the cabin and replace the side rear windows with louvers.

  5. Way to go on the Hack-A-Day story, Ben! Didn’t realize you were in the Makerspace… wish we had one here in Ohio. See you on the groups!

    DaveP in Ohio
    74 Citicar
    80 Comuta-Car
    81 Comuta-Car

  6. @asheets

    I have a VW Golf Diesel and it does 50-60mpg and has a range of over 600miles. Pretty standard over here in the UK, why do cars in the states perform so badly?

    Decent hack, but wouldn’t it be worth running a decent genny so that you could produce closer to the number of watts being used? I bet you could even produce an excess and keep going as long as you had fuel…

  7. @asheets: I can testify to that !!! my first brand new vehicle was a geo metro and it was a tough little car. my EX drove it down twice between commutes with no oil in engine !!! She would come home and say, something is “ticking” under the hood. LOL… Good thing I used Slick 50 in it. but anyway… Have you not wondered why such CHEAP & fuel efficient vehicles are not on the market anymore ?

  8. @Mike,

    Every brand has good and bad lines, but generally Onan (Cummins) and Kohler are good units, along with a few international names like SDMO.

    Generators are usually engines made by company X and electrical ends made by company Y. So you could have a good name in engines attached to a cheap Chinese made electrical end, or vise-versa. Or both being cheap. Chances are anything bought at Home Depot will be have one or both crappy parts because the quality companies just can’t compete with the cheaply made knock-offs on retail shelfs. But call your local generator sales/service center and ask what they think.

    Generators are like cars. Engines that need exercised, periodic maintenance and check-ups. You should do your homework on the quality of the brand for the price, and check to make sure there are local service centers in your area.

    Now here’s another more interesting point on the project. He did this from junk, but anyone else with some budget: You can buy portable DC generators that would be perfect for a DC car system like this, and ditch the AC-DC power supply. There’s a market created for them in keeping remote telecom’s equipment cabinets running after a storm.

  9. The problem with his propane tank is that it appears to be of the “outdoor storage only” variety which also contains an overpressure relief. These relief valves release propane gas if the tank should suddenly warm up (as I understand it, it takes time for propane to return to a liquid form, so the pressure in the tank can vary widely with temperature). These valves are used for safety purposes since the tanks are made so cheaply.

    I’ve had situations where a tank was going into relief while I was transporting the tank to/from a refill station. These tanks should ONLY be stored outdoors where the propane can harmlessly drift away. Storing them indoors (at least in the US) is asking for an insurance nightmare.

  10. For anybody wanting to make a halfass hybrid we can learn a few things from this example. Number one on the list is don’t store fuel in the passenger compartment (Think Ford Pinto effect on steroids). Number two on the list is engines are behind firewalls for a reason.

    Pull over and take a nap and recharge the batteries… Yeah right, A long dirt nap due to the Carbon monoxide you inhale…..

    I’d love to see the the fix it ticket from the first stater that pulls him over.

  11. I would have run the stock fuel tank to a gasoline (petrol for non-US) generator and dumped the exhaust through a hole in the floor of the car and bent some pipe to the stock exhaust location. I’d use some double wall pipe for the floor hole (prevent fires and such) and regular pipe the rest of the way.

    Of course I deal with much larger cars myself and the designs in my head would cost more than any of the cars are worth and be worthy only of bragging rights to say I had a 2 ton car that gets over 40 mpg. Will I ever do it? Probably not since it is financially unfeasible and the auto industry may actually have something out by the time I would have the funds to do some home brew of my own. As far as this Metro… it could stand a few upgrades for a couple of components, but all in all, it’s a good implementation and shows what you can do with less than great parts.

  12. @DerAxeman


    Anywho. Even if the piping is done right the generator should be under the hood not in the trunk as the same with the propane.

    Turn on generator. Take a nap at a rest stop. Never wake up. Attendants call police for suspicious activity. Police see propane and generator in back. Try to wake you up. Assume its a bomb. Cause a lot of mayhem for something stupid. Sounds like a good way to go!

  13. @kabadisha: Diesel is less popular in the US because the oil industry makes more money off diluted standard petrol and has far too much influence on government and regulatory bodies.

  14. As a firefighter, this looks frightening… Its rather ignorant actually. Think guided bomb. Anyone behind the wheel of this thing should keep in mind you are responsible for your actions(ie: killing someone when it blows up). That is all

  15. @kabadisha and @M4CGYV3R, diesel is plenty popular in the US for trucks but it is generally dirtier than gasoline, so it requires extra emissions control to keep smog down. There are stricter regulations against diesel engines in the US, so many foreign cars can’t be sold here. With this and the recent low-sulfur requirement, diesel fuel is more expensive than gasoline, so even with better MPG it sometimes costs you just as much in the end. The cars end up costing more too because the auto manufacturers have to put in the extra emissions controls. Don’t blame the oil producers, blame the environmentalists. (not that I think regulation is a bad thing)

    I like this hack for a pickup where the fuel and generator can be mounted external to the passenger compartment. In fact, has anyone ever heard of a small 12v DC generator that can replace an alternator? I’d love to improve my MPG by taking my alternator out of the equation, replaced with a biodiesel electric generator.

  16. Pretty cool.

    I always imagined the perfect setup would be to have a small trailer, which contains the fuel and generator, that could be hitched to the back of an electric car. Many people rarely need more range than provided by batteries, especially with a little awareness and planning; so you can leave the trailer off most of the time and not pay the weight penalty for hauling around a combustion engine. If you need more range, just hook up the trailer. Leaks or fires would be outside the car itself.

    I’m curious if anyone’s tried this approach.

  17. As for safety, keep in mind that a Geo Metro isn’t exactly known for being the safest car on the road to begin with. The propane tank will likely only make the difference between an open-casket and closed-casket funeral.

  18. There are two reasons that modern cars don’t get the same or better gas mileage than the gas misers of the 80’s (Geo metro, Honda CRX, VW Rabbit):
    1. Modern cars are considerably heaver to comply with US safety regs. The sturdier construction and safety features like ABS, traction control, 5+ airbags, etc all contribute.
    2. Those older super-efficient cars generally ran lean of stoichiometric. That left free oxygen available to combine with the nitrogen in the high heat and pressure of the cylinder, making NoX, which is more regulated now than it was in the 80s. New cars cannot pull that lean trick and still pass modern emissions standards.

  19. Firemun obviously doesn’t know just how durable a propane tank actually is.

    It will have a pressure relief valve, even if a semi slams into that car the relief valve will pop and that tank will be pushed through the front bumper before it explodes.

    Obviously there is an extreme fire hazard in that situation however.

    But you should also realize that there are placarded vehicle on the road every hour of every day which carry many dozens of much larger, less durable, aluminum propane tanks to be delivered. Not to mention that people haul these things home for their grill every day.

  20. Bill Porter: Awesome, thanks for the followup comment.

    As an aside, I only now notice that you’re responsible for the LED Lighthouse Keeper project. Awesome build and presentation.

  21. @ troy nall

    Such cheap and fuel-efficient vehicles aren’t on the market anymore because of the increased safety standards. Today’s cars are built like tanks compared to cars made before 2001 or so. Too bad the Ford Explorer had to start this safety arms race…

  22. @kabadisha
    “why do cars in the states perform so badly?”

    Because the US gallon is smaller than the UK gallon. One is 3.8 litres, the other is 4.54 litres.

    Diesel fuel contains 10% more energy per litre, which actually makes one UK gallon of diesel equal 1.314 US gallons of gasoline, which means that the US car consumes the same energy as a diesel car running 53 UK-MPG.

    So there we are. No difference.

  23. Einomies, your comment is 100% totally false. Euro cars are
    1. Smaller
    2. Lighter
    3. Run lean
    4. Have stick shift.
    There are several Euro cars that get over 65mpg US or over 79mpg Imp/Euro. We do not have those here. There were a handfull in the 80mpg US area.

    My 1989 diesel suburban now gets roughly 29mpg at 55mph highway speeds up from about 25mpg at highway speeds. What did I change? the automatic to a stick shift.

    There is much more to a diesel getting better FE than just more energy per gallon, you also gain 10%-20% because you don’t have a throttle plate. You gain from not having a lower limit on RPMs, etc. You gain from having a more efficient engine overall than gas.

    “Diesel fuel contains 10% more energy per litre, which actually makes one UK gallon of diesel equal 1.314 US gallons of gasoline, which means that the US car consumes the same energy as a diesel car running 53 UK-MPG.

    So there we are. No difference.

    Posted at 3:06 pm on Jan 5th, 2011 by Einomies”

  24. @Einomies

    Ahhh – I forgot about the conversion! That makes a lot more sense now, thanks :-)

    I guess the other thing to consider is that things in the states are a LOT further apart and there is poor rail infrastructure. Presumably meaning that people have to drive long distances, which requires a comfy car that will be bigger and heavier as a result.
    Still, I visited NYC a few years ago and the cars there are MASSIVE – the taxis are like aircraft carriers! Surely you don’t need that for city driving!?


  25. Sad… In most Europe the regulations about modifying your car are so tight that an EV conversion is almost impossible for an amateur or even a small company. Here in Spain it’s a shame. Thousands of Euros must be spent in long certification processes and tests to have your converted vehicle street-legal. And of course, you have to carry it in a trailer to those places. Some even suggested that is cheaper/faster to put your car in a trailer, drive it to Germany (!), certify it there, and bring it back.

    Bad times for Spanish hackers.

    To make this worse, here, in no case you would be able to (legally) run your car on fuel if you don’t buy it from an gas/LPG station. Automotive fuels have special taxes you pay when you buy it in a gas station. For example Diesel for heating is way cheaper than Diesel for trucks or cars, even if it’s the same liquid. Moreover, using heating diesel for your car constitutes tax evasion and you would probably go to jail if caught.

    Nice hacked hack by the way!

  26. Some have touched on this but let’s spell it out: If you want to compare EFFICIENCY of a diesel vehicle to a gasoline one, first make sure that the MPG values are both based on the same measure of a gallon (US or UK)(or better yet… join the 21st century and use metric L/100km … it makes life a lot easier). Then divide the diesel’s MPG value by 1.11 to account for 11% higher energy density of diesel.

    All other things being equal, a diesel vehicle will still come out ahead (due to higher efficiency of the diesel cycle vs the carnot cycle), but not as far ahead as you might think at first glance.

    I find all the talk about napping while running a generator in the car funny since I don’t see “napping” mentioned anywhere in the original article, nor do I think it would be most people’s inclination to nap next to something as noisy as a running generator. Nor would most people want to drive with a noisy generator running in the car (especially someone accustomed to driving an EV which is otherwise so silent).

    The value I see in the generator is being able to park somewhere, turn on the generator, go do something else, come back and have your batteries fully charged. It effectively doubles your range assuming that wherever you are going, you will be there long enough to recharge your batteries for the return trip.

  27. @IWillTry

    Agreed – most people probably wouldn’t nap next to a generator, but all the talk about napping exists because, it _is_ mentioned in HAD’s synopsis of the project.

    Regarding using L/100km as a measurement: I sadly suspect that we in the U.S. won’t fully adopt the metric system until after everyone else fully adopts English and the dollar in their countries.

  28. @Ivan

    Yeah… I was going to bring up the same thing about road taxes. It’s the same here in the US. Apparently gasoline->propane conversions were popular back in the 70’s and 80s. They seemed like a great deal, until you realized you have to pay road tax. You’ll register your vehicle as an alternative fuel vehicle, and pay yearly taxes based on the mileage you traveled in every single state.

    So to be legal, this guy has to record mileage in every state he goes to, then pay that state whatever their road tax is per mile. Note that every state is different and has different procedures. Commercial trucking companies have to deal with this all the time (it’s ‘unfair’ that they fuel up at their start and endpoint, and pay no fuel tax for the states in-between).

    Anyway, turns out by the time you do this, propane isn’t much cheaper to run than gasoline. The real kicker is going to come in a few years when they require road tax on electricity for EVs and plug-in hybrids. Right now it would be political suicide, but as states get more cash-strapped, it’s coming.

  29. Useful note: in Europe, cars typically use 94 octane high grade (and more expensive) gasoline. In North America, cars typically use lower grade 87 octane gasoline. There is your difference in consumption. And your difference in price. I drove in both locations so I know this firsthand.

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