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DESIGN & COMPONENT DETAILS
Another tempting choice for cheap batteries might be Panasonic or Powersonic or Sonnenschein gel-cell /lead acid batteries. Gel cells are the typical batteries that come with most stock electric bicycles and kits. They are not AGM. 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 AGM 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 months with no 'charge leakage.' One of the big drawbacks of of NiMH batteries is that they discharge about 1% to 2% per day. Regular lead acid batteries will just go dead in a few months as well. Because of this, AGM batteries are also marketed to people with antique cars and snow plows - vehicles that aren't used very often and are likely to have a dead battery when you finally want to start it 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 carefully 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.
an Eagle 80 amp controller from the same company. It was $120. It
due to overheating but that was completely my fault for using a much
controller. If I lived on flat terrain I think it would have been fine and
have lasted a long time, especially since I added a finned aluminum
sink from an audio power amplifier - try a decent electronics store,
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
continuous, HOWEVER it will draw a lot more than that at full throttle under load.
tend to state their controllers at intermittent current limits. For example a Scoota 120 will put out 120 amps for a short time but
not be run that high continuously.
Regenerative braking - nice idea but . . .
A lot of people inquire about regenerative braking. Hybrid car manufacturers often tout the ability to reclaim electrical energy when the car is going downhill. I don't know how much energy they are getting back in a car, but on a little electric bicycle, it is almost certainly never worth the added trouble, expense, and operational hassles. You would be much better off with a freewheeling setup. Let me explain how I've come to this conclusion.
The speed controller I use has regenerative braking available. After trying it out for a while, adjusting it and testing it every which way, I ended up disabling it.
Regenerative braking means that as you brake or coast downhill the controller will use the motor in reverse as a generator to re-charge the batteries. On my route to the market, for instance, 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. However, the regenerative braking is a function of the speed controller. If you have the regen set up for maximum regeneration, the throttle can be quite touchy. And if you just suddenly release the throttle, which is fairly normal behavior, the braking effect would be full. It is really not very good to have the throttle set up to brake that hard. I found myself about launching over the handle bars everytime I lost forgot and snapped the throttle off. Also, this is a good way to have other people ride you bike and crash it.
Note there is
on the electric side of my bicycle. A custom freewheel is yet another
surprisingly difficult mechanical part to machine or to buy. 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
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.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. I only replaced the front brake, as the rear posts are in the wrong place. A number of people have written to ask me where the rear brake is - it looks like there is no rear brake at all. Look closely in the photos: the rear brake on this GT mountain bike in mounted down low, on the chainstays, just aft of the pedal crank.Frame - I would encourage people doing this kind of conversion to use a heavy duty steel mountain bike frame. The components can take the added force and weight of the motor system. Mountain bike components now are amazingly strong and durable - they are made to take off-road abuse. The wider wheels especially are much better for the additional weight and power. Also, a steel frame is easier to weld or braze motor and battery mounts onto. Stay away from aluminum unless you can figure a way to bolt or clamp everything on without welding. Welding onto an aluminum frame will likely ruint the tempering and severely weaken it. It's quite difficult to weld on thin aluminum. My old GT was too heavy for a good mountain bike these days but just the ticket for an electric motor project. The peculiar geometry of the GT rear frame design actually makes a perfect place for the motor.
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 center of gravity 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. 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 use the pedals and just don't go any faster than a gently pedaled bicycle. It is hard to argue with that, and no one ever has.
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. The advent of affordable lithium batteries will mean that electric vehicles of all kinds will be become radically better, and immensely popular. It's just inevitable. There's already enough friction between these groups on crowded paths and trails. This is another reason why keeping maximum speeds under 20 mph is probably a good idea.
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
actually about right for a bicycle but just look at it, it's too big
heavy. There are tons of little scooters out there and it would be
possible to get a 500 watt or 750 watt scooter motor, which is would
undoubtedly work well. Currently (July 2009) I see that a 24V
Currie 600 watt motor is available for around $130. It is compact and
powerful. The MAC 600W motor might be a better choice but is $279. Try
evdeals.com for an updated motor availability. I would love to get a
Lemco pancake motor,
- they are light, powerful, and efficient but expensive. This company
now making even smaller motors that would be perfect for high-powered
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
for the tinkerer - you can change motors, change batteries, change
change gearing - it's all so easy and interchangeable compared to an
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
that thing" - you'd have to be half nuts to even consider it.
So you don't have a TIG welder and a metal lathe?
just want to bolt something onto your bicycle? As I've mentioned the
turnkey kits made by Wilderness Energy and Crystalyte seem to be the
simplest and cleanest ways to electrify a bicycle. Since I made this
have been some developments in the electric bike world. The popular
USProDrive bolt-on kit that I eschewed as too undepowered was always a
kit but I don't think it's available at all anymore. The batteries were not
quality, the stock controller was jerky and mounted inside the motor
it's hard to keep cool, and the drive train was not terribly robust, but
in all a decent kit, and they sold quite a few of them. A similar concept called Lashout seems to be available. This kit has
built-in freewheel on the motor which is nice.
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
this is not rocket science technology. This is lead acid batteries
a DC motor on a steel bike frame - this bike could
much have been made 80 or 100 years ago! Those new-fangled high pressure pneumatic tires may be the most modern component! Why has
so long for e-bikes to take off?
I offer these design
ideas to anyone who can make use of them and encourage anyone with a
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 hybrid 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 4000 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