My Electric Bicycle ProjectDESIGN & COMPONENT
DETAILS
v1.4
Another choice for cheap batteries might be Panasonic or Powersonic or Sonneschein gel-cell batteries. They are not AGM. I have been told the longevity is not as good, though the stated juice per weight ratio seems better, and they are available in a variety of smaller sizes if weight were more of an issue than range. Hawker makes slightly larger batteries such as the G16EP like my B&B which have a little more juice but are also heavier. The Hawkers are very well made. Another great thing about AGM type batteries is that they can be charged quickly at much higher amps than other kinds of lead acid batteries. Likewise they have the ability to give high current with no problems. AGM batteries are also unique among almost all battery types in that they retain a full charge for years with no 'charge leakage.' One of the drawbacks of of NiMH batteries is that they discharge about 1% to 2% per day. AGM batteries are also marketed to people with antique cars and other vehicles that aren't used very often so that their owners don't have to worry about having a dead battery when it's time to start them up.
All lead acid batteries have two big drawbacks. They are quite heavy for the total amount of power they deliver. And even these so called "deep cycle" batteries really should not be deep-cycled too often, as repeated deep discharging dramatically shortens their useful lifespan. This is where NiCads have lead acid beat, as they are more power dense and can be run down pretty much all the way without much damage. Of course large NiCads are much more expensive and must be recycled due to the toxic cadmium. So until better batteries like NiMH or Lithium Ion are more widely available in vehicle sizes and less expensive, Hawkers and other AGM type lead acid are about the best we can do. More ruminations on the Great Battery Quest below.
Batteries
and 120 amp speed
controller mounted in the main frame space.
I originally
used
an Eagle 80 amp controller from the same company. It was $120. It
failed
due to overheating but that was completely my fault for using a much
too-small
controller. If I lived on flat terrain I think it would been fine and
would
have lasted a long time, especially since I added a finned aluminum
heat
sink from an audio power amplifier - try a decent electronics store,
maybe
even Radio Shack. You need to size your controller at
about 3 times the rated power of your motor. My motor is rated at 41
amps
continuous, HOWEVER it will draw a lot more than that at full throttle.
Manufacturers
tend to state their controllers at intermittent current limits. In
other
words the Scoota 120 will put out 120 amps for a short time but
should
not be run that high continuously.
This
controller
has regenerative braking. Regenerative braking means that as you coast
downhill
the controller will use the motor in reverse as a generator to
re-charge
the batteries. On my route to the market I am on flat terrain for a
while
and then go downhill for about a mile to reach the store. Conceivably
this
could mean that I arrive at the store with nearly full batteries, which
would
make the ride back less likely to drain the batteries completely.
Regenerative
braking - nice idea but . . . Notice there is no
freewheel
on the electric side. Of course the pedal-drive
freewheel still works, which means that you
can motor without
the pedals being forced to turn. However, it
you pedal the motor will necessarily be
turning, which is a drawback if the batteries die. The regenerative
braking
function requires a solid connection to the wheel. However, after some
time with this bike, using the regen function of the special speed
controller, I came to a surprising conclusion against
using regen. As I say I bought a controller with regenerative braking.
With this set-up, I could basically use the thumb-throttle carefully as
a fairly powerful rear brake. The amount of braking could be adjusted
to make it less grabby, but I never could get it to the point where I
liked it at all. It was obtrusive and difficult to control. I suppose
if you could hook it up to a pressure sensitive brake lever, it would
work better, however, that is a bit beyond the level of sophistication
I think is really necessary on a little electric bike. Luckily the
regen function can be defeated which is what I finally decided to do.
Then with the new larger motor controller I got a box-mounted thumb lever throttle. This is just a short-throw 10k pot with a return spring and lever mounted on the end. There are now motorcycle-style twist grip throttles with built in pots widely available at scooter shops for about $50, such as the Magura.
The Scoota controller requires an on-off switch - I got a small rocker thumb switch from an electronics store, and mounted it in the throttle box.
thumb-lever throttle and on-off switch
Before this I used a Sears 12V auto battery charger, charging each battery separately. This worked fine but remembering to go out and switch the charger between batteries was very inconvenient. The EV Warrior charger shuts off automatically, the bike is always charged and ready to ride.
Weight - At 85 pounds, this is pretty heavy for a "bicycle," but I think of it more as an ultralight moped. And it is a true "mo-ped" in that you can still meaningfully pedal it. Plus I can still lift it into my pickup or my car trunk if needed. My old Peugeot moped weighed twice as much at 150 pounds with similar speed capability, and pedaling it was a joke - the pedals were geared really low, purely for starting the motor.
Brakes
-
The old brakes on this
bike were okay for 12 mph but hair-raising at 30 mph. A new side pull
"vee brake" as used on decent modern mountain bikes luckily bolted
right onto the old brake mount posts. I only replaced the front brake,
as the rear posts are in the wrong place. Regular bicycles are too
light and top heavy to use the front brake as the main
squeeze, but as any motorcyclist can tell you, on any heavier two
wheeler the front brake does 90% of
the work. The vee-brake kit was about 25 bucks on sale at a bike
dealer,
and came with a new lever for the handle bar.
The batteries also have
a very solid welded-on mount with a screw-down top retaining rail. The
batteries are heavy and need a good solid mount with shock padding.
These batteries are narrow and don't interfere at all with pedaling. In
this arrangement they
are also low and keep the CG down.
Geared for 30 mph this would technically have to be registered and insured as a motorized cycle or possibly as a full motorcycle. Not sure exactly what the difference is but I believe there is a technical distinction. However, used judiciously, most people are still going to assume that it's just a particularly fast bicycle, especially if it's being pedaled.
Actually I have no problem with a legal limit of 20 mph, although I think motor power should not be specifically limited to make hill climbing more reasonable. Slow is not bad. The wind noise is less and you can actually hear the world. A bike limited to 20 with no registration and no insurance and no driver's license (and no noise and no vibration and no gasoline and no mechanics and no smog checks and no smog and no parking hassles and no car payments . . . ) Not a bad tradeoff, to put it mildly.
I would not recommend riding on bike paths or foot trails. Most of these bar motorized vehicles of any kind, even if it's not posted. It is tempting since the bike is silent and by pedaling, most people will not even notice that you've got a motor. I think speed is the key. If I must ride on a bike path, I just don't go any faster than a gently pedaled bicycle. It is hard to argue with that.
I think eventually there will be a lot more electric bicycles and other small powered vehicles and it will probably become a problem competing with pedestrians, roller bladers, etc. There's already enough friction between these groups on crowded paths and trail. This is another reason why keeping maximum speeds under 20 mph is probably a good idea.
Motors
are already pretty much perfected, right?
Well, yes and no. My Scott motor is starting
to look like a dinosaur, it could stand to lose some weight. The power
is
actually about right for a bicycle but just look at it, it's too big
and
heavy. I would love to get a Lemco pancake motor,
www.lemcoltd.com
- they are light, powerful, and efficient but expensive. This company
is
now making even smaller motors that would be perfect for high-powered
bikes
but $800 for a motor is a bit much.
The gearing, for my use, could certainly benefit from a nice simple two-speed transmission. One speed for the hill and the other for the flat. Electric motors have such great torque throughout the RPM range that more than two speeds just isn't necessary unless the motor is severely underpowered. The obvious thing to me would be a hub motor with two or three speeds built in. I have never seen such a beast.
I think with better batteries and motor, this bike could easily weigh 25 pounds less or have twice the range, maybe both. The frame and wheels are no lightweights either, at 36 pounds. That's a good 10 pounds more than my new mountain bike, and it's got a suspension fork. So in short with modern components this type of bike could easily weigh less than 50 lbs. Performance would improve, it would be easier to pedal and you could even carry it on a car roof rack.
How about a solar cell battery charger? They sell these to RV owners. Actually there's no reason why you couldn't throw a solar cell on your roof and charge the batteries all day. Imagine - this is real-world fully solar powered transportation, doable today.
As further work on the existing bike, I would love to put a suspension fork on the front and maybe a suspension seat post. Lights would be nice. At this point this bike would be an amazing transportation unit by any standards, not just electric vehicles. Also, this starts to become a pretty intriguing possibility for a trail bike. I used to have dirt bikes but they are dirty and noisy and environmentally a big problem. A dirt bike is a blast but you're not exactly communing with nature. A completely silent electric trail bike would be much more like hiking aesthetically, and would open up long-range trails - can't wait to get some better batteries and go up to the mountains.
I can also see going to a higher voltage system. 36 or even 48 volts would be a lot better and keep the current draw down. I started with a 12 V system for simplicity's sake but the power was low and the current draw was high. I won't go into the basics of electric power except to say that lower voltage is bad because it leads to higher current which creates more heat and requires a much bigger motor controller. Controllers are basically sold by amperage or current capacity, and high amperage controllers are much more expensive than lower amperage ones. The same controller can put out twice as much power at the same amperage level if the system voltage is doubled. I have even considered simply adding another battery on this bike and just over-volting the motor to 36 volts. The motor is probably able to take it (though I'm sure the manufacturer wouldn't recommend it) and my controller can easily be switched to 36 V. The bike would be heavier, faster, and have better range. It's just a trade off. Intriguing. (Note that most controllers have voltage limitations and must be altered or jumpered to make system voltage changes.)
That's what's neat
about electrics
for the tinkerer - you can change motors, change batteries, change
controllers,
change gearing - it's all so easy and interchangeable compared to an
internal
combustion vehicle. Imagine a having an old Vespa scooter, and you
think one day
"Gee, wouldn't it be interesting to put a nice new Honda 200cc engine
in
that thing" - you'd have to be half nuts to even consider it.
Turnkey
solutions.
So you don't have a TIG welder and a metal lathe?
You
just want to bolt something onto your bicycle? Since I made this bike
there
have been some developments in the electric bike world. The popular
Curry
USProDrive bolt-on kit that I eschewed as too undepowered was always a
decent
kit that cleverly fits onto almost any bike, and includes a charger,
speed
control, throttle, battery and complete mounting hardware. This kit has
a
built-in freewheel on the motor which is nice. The batteries are not
AGM
quality, the stock controller is jerky and mounted inside the motor
where
it's hard to keep cool, and the drive train is not terribly robust, but
all
in all a good kit. Also, it is recently possible to make it
more
powerful. There are two ways of getting 600 watts out of
this
kit. One is a hop up from Thunderstruck-EV which takes the stock motor
and
rewinds it for 36 volts and adds an external controller which is less
prone
to heat shut-down. I hear it works well, thought you do need to get an
additional
battery to run the 36 volts. The second way - Scott at EVDeals sells
these
kits and will exchange the stock motor for a different 600 watt motor.
This
is still 24 volts like stock and the controller is built into the
motor.
I believe this is available in two different gearing setups depending
on
whether you want more top speed or more powerful hill-climbing. I may
try
one of these solutions at some point, provided nothing better crops up.
I have not tried either one of these kits so cannot absolutely
recommend
them, but they seem like the only good alternatives to building
everything
from scratch like I did.
Grown adults giggle when they ride my bike. It is very quiet - it's like some genie is pedaling for you. The silence is very important - it just completely changes the whole picture. You can actually hear things and stop and pull up onto the sidewalk and talk to your neighbors when you ride down the street. I have pulled up directly into my ATM booth and people hardly give me a second glance - not even thinkable on a motorcycle. Electrics are not intimidating like a motorcycle or even a scooter - to most people, they're just a bicycle you don't have to pedal. Theres no clutch, no gears to shift, no kickstarter. They aren't just environmentally friendly - they're neighborhood and people friendly.
Another amazing thing
to me:
this is not rocket science technology. This is lead acid batteries
powering
a DC motor on a steel bike frame - this bike could
pretty
much have been made 80 or 100 years ago! Why has
it taken
so long for e-bikes to take off?
I offer these design
and component
ideas to anyone who can make use of them and encourage anyone with a
garage
and some tools to make an electric bike or buy a kit or a ready-made.
At my house we have a very fast motorcycle, a car and a pickup, but the
e-bike is the most
fun - I use it almost every day.
And the most amazing thing that I have learned after all of this - you really don't need 3000 pounds of gasoline powered steel-rubber-plastic-and-glass, $30,000-120-mph marvel-of-modern-transportation-engineering to go a mile and a half for a quart of milk, a loaf of bread and a newspaper.
- Eric Peltzer
> next: early drivetrain versions - simpler and easier to build