Introduction

Dear visitor,

this page has been written to present myself and my creations for "Campus Party Europe" competition. To get a better idea of who I am and what I am doing in my life, please read following part of the text.

About me

My name is Šarūnas Šutavičius and I am 23 years old. I live in small EU country called Lithuania. I was interested in electricity and electronics since early childhood and now I have a few of my creations to show. During the school years I have done lots of hobby projects that I presented in national and international contests. Every time I presented something, I always brought home prizes and diplomas for first-third place. One of most recent events - first degree diploma for best project in European Union Contest for young Scientists, engineering section.

This is my personal website and it is hosted in my 24/7/365 running linux home server. Here you can find some of my electronics projects with photos and characteristics. I am writing everything in Lithuanian, so if you would like to take a look at it, you might want to use automated translation service. I am sorry for inconvenience, but I find out about this contest just a couple of days ago and had no time to do proper translation for everything.

If you would like to know me better, please visit "About me" page in my personal blog at http://e-motion.lt. The blog is oriented to fully electric vehicles and I am publishing my work on the topic there. More about that later on.

Project

Electric bike

Introduction

Fully electric vehicle is very hot topic these days. Most often marketing points of such vehicle are "ecology" (being marketed as "zero-emission") and "low running cost". Well, those points are true, sort of.

First of all, running cost is low only when looking at long run, at least ten years. The reason for this is battery. If you choose cheap battery, such as Lead-Acid (PbSO4), it will die completely after 100-500 cycles (full discharge and full charge) and you will have to buy new one and recycle the old. This gets very expensive, especially if we are talking about electric car. Another downsides of such battery are: very high weight, very low discharge rate, very poor low temperature tolerance and many other issues. Of cause PbSO4 battery has to be charged at least 10 hours and will die early if discharged faster than 5 hours (0.2 C rate). Many of these issues apply to most other common batteries and there are some other problems, such as memory effect in NiCd chemistry.

Because of these problems, running cost gets not so low, even during long run. If cheap (long run) running cost is required, good battery must be selected. Sincerely talking, the only EV-suitable battery at his moment is Lithium-Iron-Phosphate (LiFePO4). There are many manufacturers that produce this kind of battery and all of them differ in quality and price. The cheaper ones can be discharged ar maximum rate of 2 C (30 minutes minimum) and charged at least 4-8 hours, which is unacceptable in many applications. Of cause, these batteries are cheaper than better ones. If the battery is intended to be used in electric car with at least 200 km of range per charge, a maximum discharge rate of 2 C should be enough for everyday use, but you would still have to leave it overnight to charge fully. The best batteries I know are manufactured by A123 Systems. I say that not because I have read this somewhere on the internet, but because I personally did some testing. A123 batteries offer very high charge (15 minutes) and discharge rates (30 C continuous, 50 C peak). This is achieved by increasing conductivity of cell's electrode. One "ANR26650" (2.3 Ah) cell has ESR (equivalent series resistance) of only 8 milli Ohms. I had to build my own battery ESR tester to believe it.

The goal

The goal of this project is to build a fully electric bike for everyday commuting use. To attract wider range of buyers, the bike should be high performance, suitable to go offroad and handle aggressive riding. Of cause the main advantages over standard internal combustion bikes would be the lack of noise, smoke and stink. A huge "electrical" torque is the main factor in e-bike's performance and it drives you like a drug - once you tried it, you will never look back to internal combustion engines.

Why bike?

For electric car to have 200 km of range per charge, it would need about 50 kWh of stored energy (250 Wh/km) and this requires very big battery. One A123 Systems "ANR26650" battery cell stores about 7.4 Wh (3.25 V, 2.3 Ah) of power and costs 10 € (if bought in quantity of 500 pcs). Total amount of cells needed is 6800 pcs, and a total price for raw cells is 68'000 €, not including shipping, taxes or any other costs. These also would require complicated assembly and advanced BMS (battery management system). This kind of money is way over my hobby budget and this is the only reason I am going for electric bike project. First of all, bike requires a lot smaller amount of energy per kilometer, for example electric bicycle with 70 kg rider requires 24 Wh/km at average speed of 50 km/h (this is my personal result). Also, bikes usually do not need such high range per charge and average user would be happy with range of 100 km per charge. This is why electric bike was chosen to build. At first I was going to convert a standard scooter, but, of cause, there are serious legal issues that are preventing me from doing that. At first, scooter must be registered and have a valid number plate. To have that, scooter must have a valid MOT test pass. To be able to pass a MOT test, you need all sorts of certificates that are practically impossible to get in my country and would cost a fortune. This is why a bicycle was selected for a host. Technically, it is still a bicycle and does not need fancy certificates to run.

Work in progress

For electric bike to work, there are a few technical problems to solve. The main parts of it's electrical system are:

1. batteries
2. BMS
3. charger
4. throttle
5. motor
6. controller

For first test, a small 500 Wh LiFePO4 battery was selected. The cells are manufactured by "Phoenix Silicon Industries" and are rated for continuous discharge rates of up to 10 C.

LiFePO4, like any other multi-cell lithium battery needs a BMS, which protects cells from over-discharge and overcharge (disconnects power if any of the cells drops below 2.1V), also it monitors and balances cell voltages during the charge. A BMS is a key component to long battery life. The BMS is still work in progress and should be ready to use until April 2010.

The charger, apart from good batteries, is a key component to fast charging. For this purpose an industrial telecom charger is being used and it is powerful enough to fully charge this battery fully in only 20 minutes.

There is nothing special about throttle. Only one thing - it should be very reliable. To achieve this, it should not use mechanical potentiometer. The one with hall sensor was chosen.

Motor was chosen to be mounted inside a rear wheel, as this saves a lot of mechanical work on bike's frame and rear suspension system. For this purpose a Crystalyte x5303 hub motor was bought. It weights around 10 kg and can handle 4 kW continuous power without active cooling. This is a thee phase synchronous motor, meaning it has permanent (neodymium) magnets inside. A rim of wheel is attached directly to the rotor of this motor, so reduction coefficient is 1:1 and there are absolutely no mechanical parts that can wear off and break (except two cheap ball bearings). With appropriate battery and controller, this motor can produce a peak torque of up to 200 Nm. For such small and light vehicle, this is very high rating.

Motor is important part of the system, but the controller is a most important and complicated part. For first run standard Crystalyte three phase controller has been used. It had it's current limited to 35 amps and this was not enough to feel the power of "electric" torque, so it was increased to 100 amps. Also this controller has been modded to work with higher voltages (100 V instead of original 48 V) for future testing. This controller is very primitive so the phases are rectangular and this comes out as a cogging noise at low speeds (this is noticeable in end of video posted below), decreased efficiency and increased heat (mostly in motor). To solve this problem, I am currently working on completely new digital controller that will be able to handle power over 10 kW and will produce perfect sine wave phases. This is accomplished by implementing space vector pulse width modulation algorithm. It requires relatively huge amounts of processing power and high calculation precision, so this part gets very complicated. I am currently working on it and hope it will be ready to use until summer of 2010.

For more technical problems I have faced and been working on, please take a look at this small article on my blog. The language is Lithuanian, but automatic online translator should do a good job.

Results

After one year of prototyping, this is what has been achieved:

Yes, it's a bicycle. And yes, it has pedals. Bicycle has been chosen as a perfect host for experiments with electricity. For example, if something goes wrong during a test drive, you can always pedal your way home. Also, for first testing very small battery (only 500 Wh) has been used and those pedals really pays off when long distance needs to be covered.

Technical specifications:

• Top speed on flat (no wind): 66 km/h
• Top speed uphill: 55 km/h
• Top speed downhill: 75 km/h
• Torque: Unknown (has not been measured yet), but you have to be gentle on throttle to avoid rolling over.
• Peak power: 4.5 kW
• Range per charge:
  • 20 km @ 50 km/h;
  • 30 km if ridden gently;
  • 13 km if ridden like I stole it;
• Charge time: 1 hour (with light portable charger - 4 hours).
• Electricity cost per 100 km range: 0.30-0.50 €

This video speaks for itself:

Future plans

This video was taken a while ago (last summer) and the bike has changed a bit during the time, it is being constantly improved: new controller and battery management system are under development, also new battery will be ready to use very soon. This new battery will give it three times more range per charge, peak power (with new controller) will be increased to 12 kW (6 kW continuous) and charging time decreased to 15 minutes.

Also I am working on another EV project - electric moped. It will be used for daily commuting to work and around city, while the e-bike will be left exclusively for motocross sports and aggressive rides in forest. To read more about e-moped project, please visit my blog.