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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 :)
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]
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Can we run it on alcohol? |
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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. |
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^ 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. |
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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. |
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[DIY] What about an always on range extender that
can't power the vehicle by itself? |
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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. |
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// 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. |
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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. |
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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. |
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//Once a month you can take a Greyhound, and if
you get stuck in traffic you didn't plan your trip
well enough...// |
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The Greyhound's not gonna help you collect that
elderly relative/aquarium/Marshall JCM800 + Cab. |
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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. |
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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. |
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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. |
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This is quite a rational idea; essentially, a hybrid electric bike. |
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A 36v 12Ah Lead-acid battery weights about 15 kilos. |
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A 25cc chainsaw engine weighs about six kilos; ad another four
for the generator and electronics. |
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A 25cc engine is going to run a long time on half a kilo of fuel. |
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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. |
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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. |
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Having said all that, tiny air-cooled IC engines are not
particularly efficient, although the fixed-revs ddesign would help. |
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The fuel could be a standard can of propane or butane. … not
sure about lubrication for a gas-fuelled two-stroke though. |
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+5kg of additional adipose tissue from not pedaling
the damn bike in the first place. |
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//All it does is provide some power to take some of the load off the batteries, increasing their range.// |
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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. |
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Erm, if there's a traffic jam, the electric vehicle isn't using electricity, so why would it run out of leccy? |
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At least daytime, and LED headlight don't draw that much current, do they? |
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// a) using it to power the bike directly // |
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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.. |
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Consider an e-bike with a 500W motor. |
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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) |
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That's a total of 2500 + 1000 + 4000 + 7500 watt-minutes. |
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That's 15000 watt minutes for the hour … average 250 watts. |
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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. |
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// or b) just adding more batteries // |
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The IC powerplant will have a significantly better power to weight
ratio than equivalent batteries. |
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//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. |
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//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. |
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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. |
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// lithium- titaniate batteries // |
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LiFePo is creeping up behind their performance, already outclassing the Cobalt-flavoured type. |
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(For those of you who bought the 787, look away now ...) |
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normzone sure, as long as you can find an engine that
size made for it. |
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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 :) |
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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. |
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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. |
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MechE, not just range, but overall battery life, too. :) |
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8th there *are* small 4 stroke engines out there, I think.
Lower power, but they exist. |
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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. |
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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. |
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"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" |
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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. |
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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. |
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shades of ecky thump...strenuously tries to avoid posting Goodies youtube link..and fails. |
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//NiFe// are pretty close to Lead-Acid batteries in power and energy stats. |
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They cost more, but are nearly indestructible, last forever, non-poisonous and easily recycleable. |
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[squeaketh]’s //small backup battery// should be trickle-charged by a solar panel mounted on the back of the bike. |
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Hmmm … is the KOH electrolyte non-poisonous ? Damaging,
certainly … |
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//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// |
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sure? These seem reasonably economical <link>.
Expect a Chinese replica for a bit less. |
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^^ well you'd probably want to add plenty of lemon juice to it first. |
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To say that the electrolyte in a NiFe cell is not
poisonous is like saying that lye is not poisonous. |
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Not acidic, sure. Not corrosive, yes with respect to
most metals, which is part of why they last so long.
But not poisonous? Pfft. |
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So, what happens when you add lemon juice (an acid) to
KOH (an alkali)? Bubbling, boiling, exploding? Inquiring
minds want to know. |
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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]. |
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bicycle-> mo-ped-> electric bike-> hybrid bike.
motorcycle-> electric motorcycle-> hybrid
motorcycle. |
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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. |
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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. |
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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! |
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