Saturday, November 30, 2013

The Pope gets an Electric Bike

There are a lot of people who have eBikes now, most of them are the usual suspects when it comes to caring for the environment- Ed Begley jr, Darryl Hannah, William Shatner, Prince Charles, Leo DiCaprio, Arnold Schwartzenegger, Adam Savage, Miley Cyrus....

As a matter of fact, when Arnold got into eBikes, he also set up a $1500 rebate for the purchase of new electric motorcycles.  But that is California.


Back in July the Pope got an electric bicycle.  In this picture Dr Dieter Zetsche, Chair of the Board of Mercedes Benz, is handing over the keys to a Daimler Smart eBike.

(photo credit the Vatican)

Friday, November 29, 2013

Sustainable Hanover Transportation Expo

The Transportation Expo in Hanover on November 16 was a lot of fun.  Sustainable Hanover arranged to use the Richard Black Community Center for Saturday morning, and had several electric and hybrid cars out in the parking lot, as well as organizations like Advance Transit, Hanover Bicycle and Pedestrian committee, Upper Valley Trails Alliance, and several bikeshops, in the building.  I thought it was great because I finally got to meet Larry Gilbert of Zoombikes and try out an Evelo ebike.  There was good crowd, and another half dozen people took test rides on the solar electric cargo bike.
The temperature was a little cool at the start, but quickly warmed up under a clear blue sky, a great day for test bike rides.  Larry had both regular style electric bikes, and a trailer with an electric motor for pushing a bike along.  Hoyt Alverson brought his homemade ebike that had extra towing power, and the solar electric cargo bike held down the utility commuting side of things.
The parking lot had Toyota, Nissan, Ford, Chevy, and two Tesla electric vehicles for people to look at.

Riders were eagerly waiting for test rides on the solar electric cargo bike.

The usual result of a test ride- a big grin.

A test rider pausing to talk with friends before a test ride around the block.

Regenerative braking

I rode down to the Thanksgiving day community supper yesterday (5.5 miles each way), because I wanted to ride a bit while thinking about the design of the second bike.  I rode a regular bike so the solar electric cargo bike wouldn't get dirty (the roads have been sanded and salted).  It was a little cool- the daily average temperature was 23 F.  In addition the daily average wind speed was 11 mph, gusting to 41.  However I was very comfortable, with a polar fleece hat under my helmet, neck warmer, and work coveralls on.  (I suppose if I was more fashion conscious I might have worn ski clothes.)  The only discomfort was on the way home, as I ate too much, and did not feel like pedaling up the hills, an electric motor would have been really nice.  I noticed two things on the ride- that traction was pretty much normal, and that the regular bike (even with knobby tires) was slightly easier to pedal than the solar bike (with the motor turned off).  I'm not sure why it was easier, some reasons might be:
-the slip clutch in the electric motor is dragging slightly (with a medium push, the motorized rear wheel spins about 2 turns, and the regular bike with a freewheel spins about 10 turns)
-the cargo bike's weight might make more of a difference than I thought
-the frozen dirt roads were noticeably easier to pedal on than the softer, thawed, sunlit sections that would be more similar to previous cargo bike riding

It does point out the quantity of energy that a bicycle uses is on the small end of the scale, and small changes can make a difference.

The mpg should be more like 2500, must be going up a hill.
(My apologies to Prius owners for this display simulation.)

Regenerative braking (regen) on a bicycle looks like it will be a grey area that might get lost in smallness, and the only way to find out for sure will be measuring energy use next summer on the second bike with the direct drive motor.  (The first solar electric bike has a gear drive motor with a slip clutch, and cannot do regen.  Mid drive bikes also have slip clutches.  See my blog post about The motor for more info.)  Some considerations for now are:

To put things in overall perspective, the simple kinetic energy equation:  Energy = half of mass times velocity squared, (E=0.5mv2), can be used to compare a bike and a car.
Using data from last summer:
-the bike's average speed was about 15 mph, and an average bike and rider might weigh 200 pounds.  Stopping to 0 mph would yield 1.13 Watt hours (before system losses)
-My car's average speed was about 26 mph, and I'm estimating the weight at 3000 pounds.  Stopping to 0 would yield 51.1 Wh (before system losses)
(I used average speeds instead of traveling speeds to be more representative of all situations.)
Stopping the car yields 45 times as much energy.  The question becomes, "Does the small amount of energy from bicycle regen matter, compared to other energy flows of the bike?

To start, I'm going to refer to "Is Regenerative Braking Useful on an Electric Bicycle?" by Brent Bolton of EcoSpeed LLC:
He covers many issues that make bike regen questionable, such as:
-The large number of stops needed to get 10% more range
-System losses (averages might be: generation about -5%, charging the battery -10%, discharging -10%, giving a -25% total loss)
-A battery has a maximum rate for accepting energy, and must discard more than that (for example going down a very steep hill)
-Parasitic drag of a direct drive motor (which I'll explain more below)

I can add four more factors to Brent's list:
-From my house to the center is an 800 ft drop in elevation.  If I charge the battery before leaving home, it can't accept any of the drop as regen energy on the way down, but will still use the usual amount coming back
-Much of a bike's energy load is air resistance, which is not recoverable
-Terrain will affect regen, because long, medium descents will yield the greatest regen, full stops that are more common to flat areas are not as effective, and steep descents that dump energy will actually cause a loss.
-Since the cost of a bike's electricity is so small, perhaps the cost of regen capability is better spent on a larger battery

Parasitic motor drag is a special situation.  Regen on bikes is done by electrically switching the permanent magnet motor to run as a generator.  The motor has to be directly connected to the wheel, if there is a one way slip clutch to allow coasting, the wheel can not drive the motor for regen.  The problem is that the magnets are attracted to the steel motor poles, and without power applied they resist moving from one pole to the next.  If you have ever turned a stepper motor (such as on a computer printer paper carriage), you've felt the cogging as the magnets moved from pole to pole.  This drag on a direct drive ebike, when the power is turned off, feels like riding with a soft tire.  In a car this doesn't matter, as the baseline drag loads are large enough that a motor has to be powering the car all the time (except during braking).   However bikes spend a lot of time coasting with no motor on, they have a state in between the motor being on, and motor regen, that helps make them very efficient.  An ebike direct drive motor can be turned on slightly to give the illusion of coasting, but does the regen energy make up for this loss?

In Vermont most roads run along valley floors, with a long steep climb and then a long descent to get from one valley road to the next.  I would love to have regen instead of having to hold the brakes during the descents, would this make regen viable?  Would local urban use in WRJ be different?  Since there are so many variables, the easy answer will be simply comparing the Watt hours per mile of the second bike that has the direct drive motor with regen next summer, versus the Wh/m of the Bakfiets without regen from last summer.  An even closer comparison will also be possible using data from the Cycle Analyst data logger on trip sections.

Monday, November 25, 2013

Inside the cargo box

The cargo box was designed to fit 3 five gallon buckets, for carrying compost around to community gardens. At first the lid simply fitted over the box using rabbets cut into the lid frame to hold it on, so that I could completely remove it for large loads, or for a person or dog sitting in the box.  But it was awkward opening the box and setting the lid down while holding groceries, so I added some hinges:

This meant my dog could no longer ride unless I unscrewed the hinges, but it has turned out that I wanted the lid for most trips anyhow, for both PV power and load protection (from the wind at 35 mph, and occasional rain).

The only time the load has gotten wet was once when I didn't screw my water bottle lid on tight and put it inside the box.  Then I found out how watertight the box is.

The box is mostly cargo space.  The original design had the battery outside, but it ended up inside with all the electrical devices for weather protection, and an inside cover to restrain the battery and protect everything from getting trashed by the load on rough roads:

On the lid at left is the controller for the solar panels, and the left back wall has an ignition key and a dc to dc converter for the lights (both hard to see in this photo), the blue battery is in the center, and the motor controller is on the right.  It's good to have the controller mounted in a protected open area, as it does get warm and needs air circulation around it, however I've also seen two controllers that were mounted outside which short circuited when rain got inside them.

The slots in the back wall are for seatbelt loops for use with a child seat.

If I were to build this bike again, one of the changes would be shortening the box by 7 to 8 inches, so that it would fit just the battery and two buckets.  It has been more than large enough for carrying groceries and recycling.  Another change would be to use a monocrystalline cell frameless and glassless solar panel as the lid.  The two modifications together should lighten the bike by 20 pounds, (although also be a lot more expensive).

FlyKly market position

I've just been asked about the FlyKly again, (I think their search engine optimization people are working overtime), and thought a post about it might be appropriate.

(photo credit FlyKly)

The FlyKly is a rear wheel replacement that has the batteries and motor built inside the hub, making it very easy to install- you simply replace your bike's old rear wheel with it.  There is no wiring or connections.  When you brake going down a hill it charges the batteries, and as you pedal going up a hill it automatically  turns the motor on.  Easy installation, easy riding.

It is very similar to MIT's Copenhagen wheel, which should have been on the market by now because they had a couple year lead on the FlyKly.  They licensed it to Ducati in Italy.
Update December 9, 2013- The Copenhagen wheel is available for preorder for $699.  While it appears to have a gear drive motor which will increase it's power up hills, it doesn't have a very big battery pack and will probably not have the reserves for very many hills.  There would probably be an overheating problem on a long climb anyhow, because larger hub motors, like the one on the cargo bike, can overheat with a larger load, and they are much more open to the air for cooling.  The spokes might also have a long term tension problem, as they are bent in a U which is more likely to move.  The torque arm in the earlier pictures appears to be removed, signifying light duty use.  It is possible to buy a kit with a slightly stronger hub motor with a larger battery mounted under a rear rack on eBay for less money.  Most of the FlyKly comments below will apply. The preorder website with more information is:

The devil can be in the details.

The motor fits in one side of the hub limiting it's size, they state it is 250 watts.

The batteries fit in the other side, and appear to be 20 cells in most of the pictures.  If they are:
-LiMn 18650 cells, they will have a capacity of 80-100 watt hours
-LiCo 18650 cells would be 158-198 watt hours
-LiMn 26650 cells would be 211 watt hours

For comparison, most ebike kits on the internet have a 300-500 watt motor, and the battery packs are about 36 volts x 9 amp hours, or 324 watt hours.

My Bakfiets solar electric cargo bike was designed to carry loads, and has a motor running at 500 watts, with 720 watt hours of battery capacity.

I'm going to quote, in a review they did about the Daimler (Mercedes Benz) Smart eBike:
"Smart bike has taken a big step into the electric bike market and "looks" to be trying to hit it out of the park with it's line of new ebikes.  However because they have chosen a 250 watt hub motor, their attempt looks like it will be more like a bunt-dash to first base rather than a home run."
(The whole report is at  )

A further indication that the FlyKly is lighter duty is that they do not have a torque arm on the spindle of the hub, and rely only on the slots of the drop out to keep the axle from spinning.

Having only one speed is not that much of a handicap on an electric bike, I ride the solar electric cargo bike in top gear 98% of the time.  The motor does has to be functioning to make this possible, which means the batteries have to be charged.  A good analysis of the amount of energy available from regenerative braking on a bicycle is at:
Most riders should expect to get the majority of energy into the FlyKly batteries from plugging it into the wall, and then because the batteries have at most a 200 watt hour capacity, to have a limited to medium range (depending on individual circumstances).

A further complication is that regeneration will only work with a motor that is constantly engaged, there can't be any slip clutches that allow coasting.  The problem with direct drive bike motors is that the permanent magnets are constantly attracted to the steel poles for the windings, and this causes a slight drag when turning the motor, like riding with a soft tire.   If you have ever turned a stepper motor, (commonly used in computer printers, mechanical control systems, and small industrial drives), by hand, you have felt the cogging as the magnets jump from one pole to the next.  The result is that you cannot truly coast with a direct drive motor, when a rider stops pedaling there is a slight drag slowing the bike down.  A compromise is designing the system to have the motor turned on slightly to give the illusion of coasting, but this becomes a tradeoff between range and whatever regeneration might be produced.

I would point out two other limitations:
-Most bikes nowadays are not designed to adjust chain tension, that function being taken over by the derailleur mechanism.  In most cases the FlyKly chain will simply have a large droop and a lot of free play in the pedals, but in the worst case the chain may slip.
-Wifi or Bluetooth communications generally have a range of 300 feet under perfect conditions, and 100 feet or less under real world conditions.  This may affect the security functions of the FlyKly.

With the understanding of these FlyKly limitations I would still say there is a market for it, just don't expect it to haul loads up a hill.  If you are a lightly loaded bicyclist, who has a mainly level route, that is medium distance or less, and needs just a little extra help getting up that hill or two, this might be an easy to use solution for you.

Monday, November 18, 2013

The frame

Bicycle frames have evolved over 200 years, and there isn't much I'm going to do in my workshop to improve them.  A thin wall steel tube frame is probably the best choice for a cargo bike anyhow, as it won't fracture or splinter like carbon or wood when the bike gets dropped down some stairs, and is more easily repairable or modified than aluminum.  (I've seen projects that I've built a year or two after they were finished, and sometimes I've wondered "How on earth did this happen???")  Steel can take some abuse, which is good for a working bike that is carrying someone at 20 mph with no routine maintenance plan.

In general the walls of the bike frames I cut apart were about 1/16" thickness (0.060"), and they had a bead running down the inside of the seam, so they were not Drawn Over Mandrel (DOM).  Many bike frames are made of chrome moly (CrMo) steel, which is stronger than more common carbon steel.  (The tensile/yield properties for CrMo are around 70,000 to 85,000 psi, whereas 1020 is more like 45,000 to 60,000.)  However CrMo is slightly more likely to crack around welds, and isn't as workable.  So I used a good carbon steel and sized the tube slightly larger to make up for the psi.  It's a few ounces heavier, which will be more of a concern several bikes from now.

Down tube (behind front wheel), in jig ready for welding

One of the nice things about making a frame is that it can be made to suit the job better.  For example I used a 69 degree angle on the front fork stem, which gives slightly slower steering than most bikes, making the cargo bike more stable.  Also I dropped the crank as far as possible, to make it easier for riders to step through, or to stop and stand at an intersection.

MIG welding was used, which is not as pretty as TIG, but still serviceable.  My opinion here (Warning!) is that since abrupt changes in section create stress risers, the many ridges going across a TIG weld aren't as good as a smoother MIG weld, and the reason why either works is because the root section is so thick the stress risers don't matter.

I'm off grid, and the welding was solar powered.

The finished frame getting a coat of paint.

The frame, box, and lid were built concurrently, to make sure they fit together.  Porsche has been using water based paints on it's cars for several years now, so I wanted to try something other than the usual automotive spray cans.  Latex generally is too soft, so I tried to find some water based polyurethane at first, but it doesn't seem to be available anymore.  The final choice was a high gloss brush on exterior acrylic latex.  It works well, with some caveats:
-A good primer coat is needed or the steel will rust and turn the paint brown.
-Good prep work is needed for a good primer coat.
-It takes at least two months to dry.  The frame can be worked on the next day if you treat it very, very carefully, but it won't be hard.
-As it dries the brush strokes flatten out, and well brushed sections can turn out like automotive paint.
I'm planning on continuing to use paint like this, and improve the application technique.  A further experiment will be a clear topcoat, but that will require scheduling so that the first coat can dry thoroughly.

Friday, November 15, 2013

More Power to TRORC

Yesterday I had the honor of giving a presentation about the Solar Electric Cargo Bike to the Transportation committee of my Regional Planning Commission.  I summarized the main points of the bike, which are written about in more depth in this blog, so I won't repeat the presentation here.

At Two Rivers Ottauquechee Regional Commission

In hallway of TRORC (photo credit TRORC)

Talking with Transportation Planners about the cargo box and battery (photo credit Rita Seto of TRORC)

The other speaker was Gina Campoli, of the Vermont Agency of Transportation, giving far too short of a talk about Electric Vehicles in the state.  She highlighted the state's current population of cars, (5 of the top 7 most popular new cars are pickup trucks), and what this means for our state's Green House Gas emissions and fuel use.  The rural character of our state also puts us up close to the lead in Vehicle Miles Driven per capita.  There were 7.141 billion miles driven in Vermont in 2011, or 11,400 per capita, which is 20% above the national average.  People may have a very efficient house, but then because of our rural nature, have to drive out from it on average 7 times a day.  One of four methods of dealing with this is by switching to Electric Vehicles, (the others are improved vehicles, reducing vehicle miles traveled, and improving vehicle system operations).  Buses would come under reducing VMT, but unfortunately a housing density of at least 5 units per acre is needed to support bus service at 5 to 15 minute intervals.

Gina then covered the state EV public charging stations program, and the EV highway from Montreal to Montpelier.  Drive Electric Vermont, (a part of VEIC, a link is in the sidebar), is working on the logistics of this program, mapping the public charging stations and aiding the installation of new ones.  The EV highway is also actively being promoted by the business community, as charging stations will attract drivers, who will stop and spend time in an area.

One problem appearing is that as Vermonters use less fossil fuel, the gas tax funds for maintaining the roads will shrink.  Another loss of funds is the national trend that registrations have started to decline, particularly among young people.  At the VT Toxics Action conference last week, a young woman told me that she and her husband live in Boston and use their bikes for all transportation other than long distance, for which they regretfully own a car.  Also, I noticed that when I gave my talk about the bike that several young people from the Regional Planning Commission dropped in to listen.

The RPC is only 9 miles away from my house, but the route goes over a mountain with about 700 feet elevation change in a little over a mile.  On the way home I walked up that section, with the bike motor turned on low pushing the bike along for me.  This increased the average power use to 18.2 Watt hours per mile,  and dropped the trip's average mpg to 1850, and average speed to 11.9 mph.  It made me wonder if a mid drive motor might be better for Vermont, because the bike motor would have more leverage from being shifted down to the slower gears.  Or do I just need more power?

FIA Formula E electric racing car in front of Brandenberg Gate (photo credit Formula E)

Berlin will be the site of one of the 2014 Formula E races ( ), along with Los Angeles and Miami.  Judging from the YouTube videos, Formula E cars do make noise, mostly from the gears and smoking tires.  Perhaps they will use some of Berlin's 220 public charging stations for the pit stops, with the race cars waiting in line with the city's electric police patrol cars?

Tuesday, November 12, 2013

Preliminary Energy Analysis

I want to emphasize that the numbers in this post are preliminary.  I would not publish a report using them until more sample points are added, but these numbers are still helpful for seeing general trends.  Basic answers were figured out last summer for the most asked questions, and I've realized that it won't be until next summer that much more data is added, so I'm posting what is available now.

For a little over 200 miles during the first three months of last summer (2012), there was no measuring device on the bike.  The only energy use data from that period is from a Kill-A-Watt P3 meter used during recharging the battery with the plug in charger, and measuring the mileage when the same trip was repeated in a car.

Then I installed a Cycle Analyst, which is a speedometer meant for Electric Vehicles.  In addition to the usual speed, time, and miles, it also tallies Volts, Amps, Amp hours, Watt hours, Watt hours per mile, regeneration Amps, battery capacity and battery life cycle count:
Display panel of Cycle Analyst in center of handlebars

The bike also has a data logger with GPS tracking, but that data is for more in depth analysis.  I'll write about the Cycle Analyst and the Analogger in a future post, and for now I'll just stick with the general trends.

There were 14 trips (totaling 198.8 miles) taken in September and October that had good measurements.
-The average energy use was 13.2 Watt hours per mile.  Using the EPA conversion factor of 33.7 kWh per gallon of gas, this is equal to 2553 miles per gallon.
-The plug in charger is 85% efficient, which raises the energy use to 15.55 Wh per mile.  This converts to 2167 mpg.
-Using the GMP residential electricity rate of 14.959 cents per kWh, the 15.55 Wh per mile costs $0.00232, or about a quarter of a cent per mile.
-The usual traveling speed is 16 to 19 mph, and the average speed (all readings from whenever the wheels are turning) is 14.8 mph.
-The top speed using only motor power is 20 mph on a flat level road.
-The maximum speed was 40.9 mph going downhill.
Photo credit
-The average power use (all readings from whenever the wheels are turning) is 195.36 watts.  If the Solar Panels are producing 52.3 watts as estimated, this is about a 4:1 motor to solar panel ratio.
-Compared to a car:
      The 6 mile trip to the center takes 13 minutes in a car and 21 on the bike, or 1.6 times as long
      The 16 mile trip to White River takes 29 minutes in a car and 56 on the bike, or 1.9 times as long
-The range is about 63 miles, based on the two long trips to WRJ.
-The recharge time with the plug in charger is about 50 minutes for every 10 miles traveled.

The above numbers show that a bicycle really is a very efficient vehicle, even with a big cargo box on the front carrying a load.  This makes it a good fit for using solar energy for at least some of it's power, and suggests adding more solar panels.  It also points out the benefits of working to make it a good car substitute.

Monday, November 11, 2013

A couple more outings

Riding around at a few more events, working on the issues of being a car substitute:

At the UU church Turkey Supper, November 2.  It wasn't that long ago (less than 100 years) that people would have gone to the church by walking or riding a horse, and leaving the horse at the stables next door.

At the Vermont Toxics Action conference, November 9, at Vermont Technical College. After several minutes of talking about the bike during the power hour session, we went outside and another 6 people took test rides, bringing the amount of test rides to over 60.  The rides were around the parking lots at VTC, and were 1.979 miles total.  They used 32.7 watt hours of energy, or 0.48 cent worth of grid electricity.  As usual the end result of a ride was a big smile, except for two students from the college who were thinking overtime....

I hope the weather holds, as riding the bakfiets is still very addictive even in the 20 degree range.  I guess that I could always put knobby snow tires on:
Photo by Vermont Mountain Bike Association, of a snow ride at the Trapp Family Lodge in Stowe last winter (2012/13).  The Bakfiets might need a slightly narrower tire to fit inside the frame, but then again I'm not planning on traveling on trails.

Blog format and post subjects

Going back over this blog while talking with a few people about the solar electric cargo bike, it is a bit out of order.  I started with a general view, and progressed to individual components.  The more detailed posts are great if you are thinking about trying to build your own bike, but if you are thinking just about riding one, or complete streets, go to the beginning posts (and also some future posts will be summaries).  There are another half dozen posts planned as time permits, if you have a specific question send me an email and I will write about it sooner.

The solar panels

There was a good chance that solar panels might not work on a bike, because of shading from trees and being in valleys.  My first estimate was that the panels might produce 1/5 to 1/6 of the power needed if everything went right, enough to extend the range of the bike, but not enough to run on.  It has turned out that it all depends....  (mostly on shading), and actual performance will most likely be a bit better.
Top and Bottom views of the solar panel

36 or 48 volts are the nominal bike electrical system voltages.  These require charging voltages of about 42V or  56V respectively.  Solar panels are generally 12V (17.6V at the usual maximum power point).  There are 3 ways of connecting the panels to the bike:
-Wire the panels in series
-Wire the panels in parallel with a large dc to dc voltage converter
-Wire the panels in parallel with a small dc/dc converter on each panel

The lithium battery has a specific charging profile, so to make it easier to modify if it wasn't working right I chose the simplest and cheapest route, wiring the panels in series.  The available area for this bike's design was limited to the top of the cargo box.

The end result was 3 generic 14" x 18.5" Chinese panels that cost $49 each, that were built with Bosch monocrystalline cells that have 17.5% efficiency.  They are 20 watts each, for a total of 60 watts output at 36V.  After deducting for losses in the panels using these average output factors:
-98% PV module rating discrepancies
-95% soiling
-97% summer heating
-98% DC wiring
-99.5% diodes and wiring
The panels might be expected to put out 52.8 watts in full sunlight

The panels are controlled by a Solar Controllers Inc. 36 volt MPPT controller, and there is some interaction between this Solar Controller and the Battery Management System circuit, such that there is some energy not being used.  It is probably not much, as the controller is meant for a mobile golf cart application, and both the Solar Controller and BMS have 42V setpoints.

To verify the solar panel contribution, I need to wire a shunt into the panel output and connect it to the data logger, this is ongoing. I will write more about this in a future post about the Cycle Analyst and data collection.

There are several improvements that could be had by going to a 48V system on the next bike, but it appears that costs will also at least double due to a more sophisticated system.  When the design is worked out I will put up another post.

Likewise, some significant benefits could be had by going to frameless and glassless mobile application solar panels, (estimated 18 pounds of weight savings), but they would cost about 4 times as much.  The market is changing, so this may work out to be a near term option for the second bike.
Enecom Semiflexible frameless and glassless mobile application monocrystalline solar panel

The long term (14 trips) average energy usage of the motor (any time the wheels are turning), is 195.36 watts.   Using the estimate of 52.8 watts for panel output, the motor to generation watts is about a 4:1 ratio.  Again, until the shunt is installed on the panels, and some time is spent analyzing the results, I won't have a shading factor for Vermont roads.  It can be estimated simply by looking down a road and seeing how much of the pavement has a shadow on it, but this is not as accurate as long term measurements would be.  For now I am using the simple equation that if you ride for half an hour, then park in the sun at your destination for 2 hours, (4 times as long), it will charge the battery back up.

Thursday, November 7, 2013

The battery

At the beginning of the project, I planned on using an old car battery that I had in the barn.  It would have saved me a lot of money, but it would have been the death of the project.

At first the low budget route seemed good, reusing something I already had.  But after reading some mileage claims, I decided the bike needed a fair amount of energy to get to WRJ and back, (33 miles with no side trips).  The old car battery might have had maybe 300 watt hours capacity left in it, and besides it was only 12 volts- the motor needed 36 or 48.

A short side note here:
As previously mentioned, Amps is like the water flowing through a pipe, and Volts is the pressure (zing) pushing the water.  The two have to be combined to get the total amount of power, and this is done by simply multiplying them together to get watts.  If I let 20 amps of electrons flow out of a 12 volt battery, there is 240 watts of power flowing.  If the battery produces that flow for an hour, (this changes the flow into a fixed quantity), the amount of energy produced is 240 watt hours.  The more the volts, the more the amps, and the longer the time the battery lasts, the more capacity it has.

(photo credit Jingneng Battery)

The nice battery pack in an aluminum case under a bike luggage rack that I mentioned while talking about range is probably 36 volts x 9 amp hours, or 324 watt hours.  I wanted more.

Lead acid batteries (like my old car one) have a few problems.  They are heavy (like lead), spill sulfuric acid, and don't like being drained below half full (they die).  Golf carts use deep discharge cycle versions because they are cheaper than other batteries, and it is ok to carry around 250 pounds of batteries under their seat.  A sealed lead acid battery prevents spilling acid, but still dies if discharged too much.   The consensus on most forums about lead acids was that they last only one year, because no one stops themselves from draining it all the way to empty.   At a Lead acid battery a year, a lithium battery that lasted 3 years would actually be cheaper, and not have the draining problem.

You will notice that I've jumped over NiCad and NiMh batteries.  NiCads are quite toxic, have a memory, and don't come in big assemblies.  NiMh are better, but why not just go to Lithiums?

Most Lithium battery charts look like this (right click on chart and open in new tab to get a larger version):
(Similar versions of this chart are used by several Chinese battery and ebike motor manufacturers.)

Or like this:
(Chart by a Sun Trip commentator, who was traveling on an electric bike from Shanghai to Lille, France.)

In addition to LiFePO4 being an obvious good choice, it is also available in Prismatic Pouch cell format:
(Top photo by Cedax, bottom photo by Cycling-2013, cells are about the same scale.)

While a cylindrical cell allows air to flow through a stack for cooling, (good for preventing Priuses from catching on fire), the LiFePO4 chemistry doesn't really need it.  The Prismatic Pouch cell takes less space on a bike, and is lighter.  In addition, they are actually connected to the US, as A123 is from Massachusetts, (although the cells in my battery probably came from a plant in Korea).  A further feature is that LiFePO4 is similar to the naturally occurring mineral Olivine, and is relatively low toxicity.

The Prismatic Pouch cell comes in a 20 Amp hour size, and assembling them in series with a battery cell monitoring circuit for a nominal 36 volt battery gives 720 watt hours of capacity.

The cells were assembled into a battery in Shenzhen, China (photo credit Concrete Jungle)

Assembled battery with charger (photo credit cycling-2013)

The battery has foil faced foam board sides held together by blue heat shrink tubing.  This is a step up from the cardboard and duct tape wrapping that many cylindrical cell battery manufacturers use.  It has worked very well for about 450 miles this summer and fall, and the only bad comment is that the charger was squashed during shipping, and I had to pay $25 more and wait 4 weeks for a replacement before I could charge and use the battery.

Wednesday, November 6, 2013

The motor

The motor helps make this bike a car substitute.  There are several decisions:
-Front or rear wheel (and since I started this project, mid drives have become more popular)
-Geared or Direct Drive
-Size (300 to 1000 watts)
-Throttle control or Pedelec
-Price vs quality

I'll run through the main considerations:

A lot of bikes have a front wheel motor, as it doesn't involve the freewheel and chain.  However the rear triangle of a bike frame is much more solid than a front fork, and since the cargo bike design included carrying loads, I choose a rear motor.  A secondary factor is that many of my roads are dirt and sometimes steep, and I expected a front wheel motor to be more likely to spin.  (There are bikes with a motor on each wheel for all wheel drive.)  A note: both locations need a torque arm, especially aluminum front forks, unless you have a very small motor that you never turn on full.
Torque arm (black metal piece from axle to frame) that stops axle from spinning in dropout.

A geared motor has a smaller hub inside it carrying the magnets, which spins much faster than the wheel. Then gears slow down the motor speed to the wheel speed, giving a lot of torque at low speeds. However the gears would make coasting next to impossible, so a one way slip clutch is added.  This allows coasting like a regular bike, but does not allow any regeneration on braking.
One way slip clutch in center, with 3 planetary gears riding on it.  The motor gear fits in the center of them, and the outer ring gear is on the bicycle wheel inside where the spokes attach.

A direct drive motor has the magnets attached directly to the wheel hub, and has to be a larger diameter (and heavier) to give the magnets enough leverage.  Very simple, with no gears:

Direct Drive hub motor, left- magnets on casing, right- the inner stationary coils (unsure of photo credit)

Direct Drive lets the motor function backwards as a generator, and pump electricity back (Regen) into the battery when going down hills. There is not much energy available on a bike from doing this, I'll cover it more in a Regeneration post. Also the magnets are constantly attracted to the coils in the motor, and if the motor is not turned on it is harder to pedal, like riding with a soft tire.

Mid drive motors (connected to the front sprocket near the pedals) have been made mostly by Panasonic for the Far East market, however in the last year Bosch, Contitech, Benchmark, and Yamaha have come out with motors, and there are also several aftermarket kits, like Stoke Monkey. I originally ruled out mid drives because they can be complicated, and they use the standard chain and sprockets to transfer power, which seemed less robust than a hub motor.  However they do have two advantages:
-A very big motor can be squeezed in behind the seat for racers
-A small motor also works, because you shift down for hills

A Pedelec system turns the motor on only when the rider is pedaling, by using pressure sensors on the pedals or sprocket.
Sprocket with torque sensor for Pedelec system (unsure of photo credit)

Several European countries require this system.  The solar electric cargo bike uses a hand throttle instead which allows riding without pedaling.  However if done well, (such as Bionex), a Pedelec can be a lot of fun to ride with no constant control needed from the rider.  It is also a natural fit with a mid drive system.   I may have to build a fourth bike to test this out.

Amps are like the water flowing through a pipe, and Volts are like the pressure pushing that water.  On an electric bike you get the same amount of push by turning one down and the other up equally, and in general higher voltage/lower amps is the way to go.  This direction allows thinner wires, which reduces cost and makes the bike lighter, all the way up to the point where the motor burns up because the insulation can't handle the voltage.  Most electric bikes are using 24, 36, or 48 volt battery packs, and I chose a middle of the road 36 V battery for the bakfiets.  It's motor can probably handle over 100 volts, the limit here is set by the controller:
Infineon ebike motor controller

The power section of this controller is rated for 52 V, so I could also use a 48 V battery pack.  This controller is programmable, and I can set several operating parameters.  The bike is currently set up as a 500 watt bike, (36 volts x 15 amps = 540 watts), and this is proving to be a decent amount of power for getting up hills.

The motors I chose are very good quality, but more expensive than the kits being sold on Ebay.  I did this for a few reasons:
-The motors have the capacity to go up to 1000 watts under continuous use.  Although only 300 W is needed on a flat road, I wasn't sure what would happen on hills with a loaded cargo box.
-I knew the bikes were going to be loaned out, and wanted some safety margin so no one was stranded
-The bikes are an experiment, and being able to program the motor controllers is useful
-The seller had high recommendations, and was able to let me choose rim size and type, motor torque and speed, controller specs, and throttle control
This setup is medium heavy duty.  If I was building a bike with no racks for around town use, one of the lighter kits on Ebay would probably be ok.

Monday, November 4, 2013

Organizing the project

There are not very many solar electric cargo bicycles where I live.  As I started to collect information about them the summer of 2012, I asked at bicycle shops between here and Montpelier, talked with other energy committee people who were Electric Vehicle enthusiasts, and asked Transition Town bicyclers.  Entering that winter I had a list of 21 people who wanted to be involved in the project in some manner, with about half of them willing to be test riders for a week or two and write a report on whether they used the bike or their car and why.  From the start there was a lot of interest, and it seemed like many people would be involved.

There was also a definite scarcity of knowledge, so it seemed like these bikes might end up as a public education program, like Solar Hartland had been.

I had also started to collect used bikes early on, and after putting a notice on my town's listserv looking for more parts bikes, ended up with 27 bikes (and several additional people who wanted to be part of the project):

Some of the parts bikes

About the same time, I started to become aware of how expensive this project might be.  Since so many people were involved, I asked for permission to run it as a town energy committee project, and then applied for a $1000 grant to cover the batteries and some of a motor.  The precedent was a pair of Transition Town bicycle blenders that I had been loaning out to various community groups for the previous 5 years.  The grant wasn't approved because they felt there wasn't enough community involvement, which turned out to be true: When I had to care for family members during the summer, Bob and Chad were able to do some of the welding, but without me designing the pieces the project slowed to a crawl.  So I sucked it up and bought both motors, (it is always better to have the parts in hand for measurements when building a frame), and postponed the batteries for a few months.

Carefully taking bikes apart....   :-)

Ever take something apart and think "I'm not putting that back together again"?

Unfortunately the battery was needed sooner than planned to finish up the frame dimensions, resulting in my skipping church donations, etc. for a while.  The motors came from Hong Kong (the company was a delight to deal with), and the battery from Shenzhen (the company might have been ok, but the shipping company squashed the charger and things went downhill from there).  I'll write more about this in upcoming motor and battery posts.

Another item that didn't work out as planned was the parts bikes.  Only about half of the parts were usable, and many shifter or other parts were unique to a manufacturer, so a lot of bikes were needed to get a whole bike. Also only about half the frame tubing could be reused, as many of the cut pieces were a few inches too short.  It is necessary to put together one good bike, and then plan on purchasing new tubing and repair parts as needed to convert it.

One of the bikes had this sticker on it:
I had heard of them before (a local baker, Kelly, has adapted it to "Bread not Bombs") but wasn't familiar with them, so I looked them up on Wikipedia.  They are in Boston, and have been around since 1984!  I can only imagine how many used bikes they must have to go through to produce a shipment.

Eventually the bakfiets was presentable, in time for the Fourth of July (2013) parade.  Other events have included:
Extinct North American Camel meets Solar Electric Cargo Bike
at Sculpturefest 2013, Woodstock, VT,  

Helping out the Dartmouth Sustainable Group at Move In Day
as part of the Upper Valley Sierra Club.  The student's portable power
solar panel project on a tricycle is visible to the left of the cargo bike.

Visiting "The Li of You and Me" community art show at the Library.
(Poster delivered on the cargo box top.)

Hanging out watching the bikers and runners at a water stop at the Vermont 50 mile race.

Test rides at the Hartland Farmers Market Fall Festival.

The bakfiets ended up putting on close to 450 miles this summer and fall, about half of which had good records made of the energy usage.  (I'll write more about that in an Energy Flows Budget post.)

There were many fun moments, like walking out of a regular supermarket, throwing the bags of groceries in the box, and riding off with shoppers looking on.   About 50 to 60 people took test rides, and about a dozen times I heard riders say "WOOOOO" from a quarter of a mile away once they figured the bike out.  If they didn't come back with a big grin, I knew they had missed turning on the motor somehow, and repeated the instructions and sent them back out again.

There are other events and conferences still coming up this year, but because of the delayed building schedule the loan trials did not happen.  I'm expecting the longtail will be done next summer, and once the second battery is purchased, the loan trials will take place.

Sunday, November 3, 2013

The design- usage

I know two people (Nancy and Laura), who routinely ride their bikes between Hartland and White River Junction (my 33 mile goal).  They most often are commuting, but occasionally they carry loads on front or rear racks.  They are much fitter than I am.  I used them as role models for this project, with the qualification that my bike was going to have to help me out a bit.

There are also hundreds of thousands of people in Amsterdam and Copenhagen racking up about 2 million kilometers each day on bicycles.  They can't all be fit, and they are going to work in work clothes.  On their upright posture bikes, people wear skirts and suits.

When I was a kid, an "English" 3 speed was the bike to have, (with derailleurs becoming more common just before I got my car license).  These were practical bikes, I rode mine for miles around town, including shortcuts through wood paths, corn and potato fields, and miles of state forest maintenance roads.

Strictly speaking, a regular electric bike would probably do my current errands with some fussing during packing the loads, but the pick up truck nature of the bakfiets makes it much easier.  A few things I've carried (like 30" x 40" foam core energy committee posters) will probably be easier on the longtail, the only place for them on the bakfiets is taped on top of the solar panels.

During initial layout of the dimensions, Karen asked for the bike to be able to carry compost in 5 gallon buckets.  I designed the cargo box to fit 3 buckets, but then moved the battery from outside to inside the box, so it now it only fits 2.  If I were to build another bakfiets, I would shorten the box several inches to just fit the 2 buckets and battery.

I've ridden in pouring rain, and the inside of the bakfiets cargo box stays dry, but overall weather is another issue.  I have a few ideas, but they are going to have to wait until the third bike.....

Just kidding! This is a trike, and I'm sticking with two wheels!  (This photo appeared on an Italian blog and I'm unsure of the photo credit.)