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E-Bike Range Extender

Small gas engine keeps battery charged
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Let's suppose that you start with either an electric bicycle, or with a bicycle with an electric pusher trailer.

Now, add to that system, a small charger, powered by a repurposed model car engine (something in the 10cc range).

When your battery gets low, and you're away from home, flip a switch (or yank the starter string), and the engine starts and charges the battery.

Pedaling is reduced or eliminated, which is the whole point of having an electric bike, and fuel consumption shouldn't be very high (since the engine is so small).

Obviously, it's we'd want to use an engine which can run on straight gasoline (or a gas/oil mix), since nitromethane is expensive.

Basically, it's the bicycle equivalent of an electric car with a gas range extender.

Now, obviously larger engines will work with this idea, but if you plan to build this, make sure to check your local laws to know what's the biggest engine you're allowed to stick on a bike, or, make sure you know who to bribe to overlook it :)

goldbb, Mar 13 2013

Sterling engine battery charger Sterling_20engine_2...my_20mobile_20phone
[not_morrison_rm, Mar 13 2013]

ecky thump http://www.youtube....watch?v=TJxGi8bizEg
[not_morrison_rm, Mar 14 2013]

25cc Honda engine http://www.brandnew...es.com/GX25-S3.aspx
[bs0u0155, Mar 15 2013]

Faster charging edison cell http://gizmodo.com/...e-1000-times-faster
Graphene makes everything better :) [goldbb, Mar 17 2013]

[link]






       Can we run it on alcohol?
normzone, Mar 13 2013
  

       After doing the math on this myself I have decided that range extenders are stupid (no offense to the OP). A generator powerful enough to charge the batteries of a vehicle can just power the vehicle by itself, and use less gas. Case in point: the Chevy Volt can go about 40-50 miles on its electric charge. When the charge runs out the pitiful little engine revs itself up to high rpm and the car gets 30mpg, which is worse than it would with just the small gas engine. You're just better off to spend that extra weight and space on more batteries to make it go farther. Now before anyone gets their panties in a bunch I know - the point of the gas engine is for when you can't take the time to charge it. I would argue that if that is a problem to begin with then an electric vehicle is not for you. If you only travel short distances then great, get an EV. If you travel long distances just get a fuel efficient gas vehicle.
DIYMatt, Mar 13 2013
  

       ^ but what if you're unexpectedly stuck in rush hour ? or your destination is 1/2 a mile outside the operating range, or while your range is 50mi you make a once-a-month trip of 100mi.
FlyingToaster, Mar 13 2013
  

       If the gas runs out? You could add an extender for that too - a small backup battery drives an electrical process to split water into hydrogen and oxygen, and the hydrogen goes into the motor as the backup fuel source.
sqeaketh the wheel, Mar 13 2013
  

       [DIY] What about an always on range extender that can't power the vehicle by itself?   

       Maybe it's not actually always on, but if you know it's a longer trip or even close to the range, you start it when you start your trip or at an arbitrary battery capacity. All it does is provide some power to take some of the load off the batteries, increasing their range.
MechE, Mar 13 2013
  

       // if you get stuck in traffic you didn't plan your trip well enough// or the accident that's caused the tailback wasn't planned well enough.
MaxwellBuchanan, Mar 13 2013
  

       I still think it would be best to adopt the Sterling engine battery charges idea, and strategically hide coils with magnets on the propshafts on the undersides of cars on your usual route.   

       That way, if you go low battery, you have merely to shimmy under one of the vehicles and recharge. Just pretend you're with the TSA looking for something and say it's classified, no one will ever guess.   

       Or just bigger wheels?
not_morrison_rm, Mar 13 2013
  

       //Once a month you can take a Greyhound, and if you get stuck in traffic you didn't plan your trip well enough...//   

       The Greyhound's not gonna help you collect that elderly relative/aquarium/Marshall JCM800 + Cab.   

       Traffic CAN be unpredictable, and a peppering of electric cars running out of range are going to make things worse. Traffic problems tend to synergise and form positive feedback loops anyway, so having more sensitivity in the system is a poor idea.   

       This may be the result of poor planning, but people run out of petrol/diesel everyday, and those cars have 8-20 fold more headroom... in the Volt, the range extender's a good idea.   

       This idea however, is poor. In an electric bicycle, the range extender is your legs... even better it's got a terrain-responsive route-optimizing brain attached. Adding an additional layer... 3 in all, is an over complication.
bs0u0155, Mar 13 2013
  

       This is quite a rational idea; essentially, a hybrid electric bike.   

       A 36v 12Ah Lead-acid battery weights about 15 kilos.   

       A 25cc chainsaw engine weighs about six kilos; ad another four for the generator and electronics.   

       A 25cc engine is going to run a long time on half a kilo of fuel.   

       The biggest problem is going to be a battery that can accept all the energy pumped into it from the generator without boiling its electrolyte.   

       A very small IC engine with a battery makes good sense in that the engine always runs at its most efficient revs, irrespective of the speed of the bike.   

       Having said all that, tiny air-cooled IC engines are not particularly efficient, although the fixed-revs ddesign would help.   

       The fuel could be a standard can of propane or butane. … not sure about lubrication for a gas-fuelled two-stroke though.
8th of 7, Mar 13 2013
  

       +5kg of additional adipose tissue from not pedaling the damn bike in the first place.
bs0u0155, Mar 13 2013
  

       //All it does is provide some power to take some of the load off the batteries, increasing their range.//   

       That was my first thought. But, in order to meaningfully increase the range the gas generator is going to be so large and powerful that you would be better off a) using it to power the bike directly or b) just adding more batteries.
DIYMatt, Mar 13 2013
  

       Erm, if there's a traffic jam, the electric vehicle isn't using electricity, so why would it run out of leccy?   

       At least daytime, and LED headlight don't draw that much current, do they?
not_morrison_rm, Mar 13 2013
  

       // a) using it to power the bike directly //   

       No, because then the powerplant would have to be rated for the peak load under acceleration, rather than the average load- including in the average periods when the bike is stationary..   

       Consider an e-bike with a 500W motor.   

       For a 60 minute journey, the bike spends 5 minutes accelerating (500W), 5 minutes stationary, 10 minutes running downhill (100W) 10 minutes going uphill (400w) and 30 minutes running on level roads (250W)   

       <frantic scribbling>   

       That's a total of 2500 + 1000 + 4000 + 7500 watt-minutes.   

       That's 15000 watt minutes for the hour … average 250 watts.   

       So a 200 watt generator can nearly cover the power demand, buffered by the batteries; compares favourably with the bigger, heavier unit needed to handle the 500w peak load.   

       // or b) just adding more batteries //   

       The IC powerplant will have a significantly better power to weight ratio than equivalent batteries.
8th of 7, Mar 13 2013
  

       //the Chevy Volt can go about 40-50 miles on its electric charge. When the charge runs out the pitiful little engine revs itself up to high rpm and the car gets 30mpg// The gas-only mode EPA mileage rating for the Volt is 35 mpg city, 40 highway. ICE->generator- >electric motor->wheels powertrains are not inherently much less efficient, and in practice are often more efficient, than ICE->mechanical transmission->wheels ones. They’ve been the drivetrain of choice for railroad trains (nearly as far as we can get off the topic of bicycles) for decades.   

       //The biggest problem is going to be a battery that can accept all the energy pumped into it from the generator without boiling its electrolyte.// The magic technological solution for this is lithium- titaniate batteries. Because these batteries change the shape of their molecules less than others, they generate less heat when charging or discharging, so can be charged much faster - in suitable-for-car-size and smaller sizes, to 90%+ in about 10 min. Given this performance, the problem with these batteries is usually that available chargers aren’t powerful enough, not that they’re too powerful.   

       Like many magic tech solutions, lithium-titanate batteries are expensive and slow to market. To the best of my knowledge, they’re available only in very expensive, rare electric cars, and a few now-discontinued electric-assisted pedal bicycles. Rumors that the Honda Ev-neo would have them appear false.
CraigD, Mar 13 2013
  

       // lithium- titaniate batteries //   

       LiFePo is creeping up behind their performance, already outclassing the Cobalt-flavoured type.   

       (For those of you who bought the 787, look away now ...)
8th of 7, Mar 13 2013
  

       normzone sure, as long as you can find an engine that size made for it.   

       FT, if you're unexpectedly stuck in rush hour, then a purely electric vehicle will use no more energy from it's batteries than it would when moving at full speed. But your other points hold :)   

       Add to that, a hybrid vehicle that runs in charge charge maintenance mode (with a low power ICE which always runs, slowing down the rate that the batteries get drained) will have a much longer battery lifespan (more charge/discharge cycles) than one which runs solely as a range extender. And since batteries aren't cheap, the ICE is a good thing.   

       squeaketh, the range extender for the ICE running out of fuel is your feet on the pedals. It *is* a bicycle, after all, not an electric motorcycle.   

       MechE, not just range, but overall battery life, too. :)   

       8th there *are* small 4 stroke engines out there, I think. Lower power, but they exist.   

       CraigD, If I were going for high-tech batteries, I'd choose Axion's Lead Carbon cells. Sure, they're heavy, but they've got an amazingly long lifespan.   

       For low tech long life rechargeables, they still make Edison cells. They've got an amazingly long lifespan, too, and one can add some catalytic battery caps, to reduce electrolyte boil-off.
goldbb, Mar 13 2013
  

       // Edison cells //   

       "Due to its low specific energy, poor charge retention, and high cost of manufacture, other types of rechargeable batteries have displaced the nickel–iron battery in most[ 7] applications.[ 7] applications"   

       If NiFe cells were practical for mobile use they'd be commonplace. About the only time they're used for thiat is rail locomotives and stacker trucks.   

       Yes, there are really tiny 4-stroke engines. But they are far too beautiful and precious to hide away on the back of an e-bike.
8th of 7, Mar 14 2013
  

       shades of ecky thump...strenuously tries to avoid posting Goodies youtube link..and fails.
not_morrison_rm, Mar 14 2013
  

       //NiFe// are pretty close to Lead-Acid batteries in power and energy stats.   

       They cost more, but are nearly indestructible, last forever, non-poisonous and easily recycleable.
FlyingToaster, Mar 14 2013
  

       sound cooler too.....
bs0u0155, Mar 14 2013
  

       [squeaketh]’s //small backup battery// should be trickle-charged by a solar panel mounted on the back of the bike.
pocmloc, Mar 15 2013
  

       // non-poisonous //   

       Hmmm … is the KOH electrolyte non-poisonous ? Damaging, certainly …
8th of 7, Mar 15 2013
  

       //Yes, there are really tiny 4-stroke engines. But they are far too beautiful and precious to hide away on the back of an e-bike//   

       sure? These seem reasonably economical <link>. Expect a Chinese replica for a bit less.
bs0u0155, Mar 15 2013
  

       ^^ well you'd probably want to add plenty of lemon juice to it first.
FlyingToaster, Mar 15 2013
  

       To say that the electrolyte in a NiFe cell is not poisonous is like saying that lye is not poisonous.   

       Not acidic, sure. Not corrosive, yes with respect to most metals, which is part of why they last so long. But not poisonous? Pfft.   

       So, what happens when you add lemon juice (an acid) to KOH (an alkali)? Bubbling, boiling, exploding? Inquiring minds want to know.   

       Also, while conventional Edison cells (which are what I was thinking of when I wrote that anno) have power density and energy density similar to lead acid cells, there's a new version in developement which charges 1000x as fast, see [link].
goldbb, Mar 17 2013
  

       bicycle-> mo-ped-> electric bike-> hybrid bike. motorcycle-> electric motorcycle-> hybrid motorcycle.   

       The mo-ped worked because it was light, so you could pedal it if you ran out of gas or needed to assist the engine up a hill.   

       Could an electric bike (e-ped) be made light enough to pedal any reasonable distance? And could braking and pedaling forces be diverted to charging the battery (and still allow forward momentum of the bike)? Maybe the answers lie in the 8th of 7's post.   

       I think that a battery, gasoline motor, and pedals (an emo-ped) is not going to be something an electric bicycle owner will be able to pedal. So, if you remove the pedals you have (as others have mentioned) a hybrid scooter/motorcycle, which may be just fine!
crok, Mar 25 2013
  
      
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