More Pictures &

Data and Test Results

Below are some thumbnail pictures at various stages of the build process.  I found the project to be quite a bit of work but I enjoyed every minute of it.  Whenever possible, I tried to make improvements to the vehicle.  

Changes and Enhancements I Made

The major changes that I made to the stock BugE are as follows;

Calculated Performance

Below is a cut and paste of the spreadsheet I built to determine the probable range and other performance data of my Lithium BugE.  This was built before I completed the vehicle and before I performed any tests.  The data is 100% reliant on the stock BugE baseline where the stock BugE travels 30 miles at 30mph.   In a nut shell,  I would need to determine the ratio of the energy that I had available over the energy available for the stock BugE then factor in the various efficiency gains to deduce the performance I would likely achieve.

 Here is a brief explanation of the data;

• Battery Capacity - This is simply the manufacturers rated battery or cell capacity.

• Peukert Exponent - This is critical in a calculation that determines the actual energy available in lead acid batteries, adjusted down using a Peukert exponent.  I got the Peukert exponent from the manufacturer of the Optima batteries because it was not noted on any data sheet.  Lead Acid batteries are normally rated based on a 20 hour rate.  For the battery used in stock BugE, the 20 hour rate assumes a discharge fixed current of 2.75 amps.  That's 55ah/20 hours.  At higher current draws, the capacity (available energy) is less when the Peukert calculation is performed.

• Peukert Adjusted Capacity - When the Peukert Exponent is used based on an average current of 45 amps (real world stock BugE numbers at 30 mph), the battery's capacity is actually only 48ah.  That is extremely important in baselining the stock BugE.

• Adjusted Stated Capacity - I added this to allow me to adjust ( up or down) the manufacturer's stated capacity.  For example, the Thunder Sky batteries seems to exhibit a higher capacity at lower discharge currents.  

• Average Voltage - The nominal or average voltage of the battery or cell.  This number is different at different discharge currents.  I determined that my nominal cell voltage is around 3.35 volts.

• No of Batteries - Counts of cells or batteries.

• Motor Efficiency - From manufacturer's data sheets or directly as stated from manufacture's engineers.  Unfortunately I only have data for a 48 volt system.  I am assuming that since my system voltage is about 80 volts, the motor efficiency is >89% and likely in the low to mid 90s.

• Controller Efficiency - Same as above.

• Efficiency Gain by Voltage - My best guess at using a higher voltage system.

• Energy Recovery - My best guess of the recovered energy as a result of regenerative braking.

• Adjusted System Efficiency - (Motor Eff. X Controller Eff.) X (1+ Eff. Gain by Voltage + Eff. Gain by Regen)

• Adjustment Factor - Adjusted Eff. Gain/ Stock BugE Eff.

• Range at 30mph - My Usable Energy/Stock BugE Usable Energy X Adjustment Factor X 30 miles

• Range in km - The above X 1.62 to determine km

• Watt-Hours per Mile - Total Energy/Range at 30mph.  Excludes charger losses and battery absorption losses.

Actual Performance 

To perform a reasonable range test I prepared the vehicle to ensure optimal performance by ensuring the batteries were fully charged, the tires were filled to near maximum pressure, toe in was not excessive, etc..  I decided that I would drive conservatively but in a reasonable manor such that I would not impede any traffic flow.  I realized before I started that I could not test the vehicle at an average speed of 30mph.  I simply had no roads accessible to me where speeds are that low for long stretches.  As well, I would face many stops and starts and some small hills.

I began the test on a late Saturday with my speed varying from 50kmh to 70kmh.  There were lots of stops and starts and sometimes I needed to accelerate hard.  My battery depth of charge indication was not accurate at this point so I was going to rely completely on the battery pack voltage and on my first low cell warning.  Each of the 24 element circuits continuously monitor each of the cell's voltage very accurately.  If any cell drops to 2.8 volts or less, my LCD display would show me the warning.  The reason I selected 2.8 volts as my low cell threshold is that the PIC processors I used in my element circuits would not measure the voltages as accurately as I needed at 2.5 volts.  However they are extremely accurate at 2.8 volts and upward. Choosing 2.8 volts would also give me a bit of reserve energy, just enough to find an electrical outlet for a recharge.

I reached 162 km and was ecstatic as this was the 100 mile point and the indicator (to me) of success.  I couldn't believe it went this far.  I really thought that the higher speeds and stops and starts would not allow for such a range.  I had not received any low cell warnings at this point and the battery pack voltage was still around 78 volts with just a bit of fluctuation.  I realized that 200km may be possible.  This was really neat because I was driving the vehicle in a conservative yet practical manor.  I had almost made 200km when I received the low first low cell warning.  The Lithium BugE had traveled  199.6km just short of the 200km mark.  The low cell warning had come when I accelerated through an intersection.  If I had been coasting, I would have beat the 200km mark.  Regardless, I was thrilled that my numbers were close and the Lithium BugE performed perfectly. 

Below is the actual test results.  I should point out that the actual charger efficiency (when I determine it) will likely result in an adjustment to the Whrs/Mile and equivalent MPGs.   

Lithium BugE Test Results

Conclusion and Thoughts

There was a lot of steps that I did not discuss because my intent was to make this website brief.  There are a  lot of details regarding assembly of the vehicle, making the canopy, building the steering column, steering stabilizer, tie rods, adjustable seat, making the custom fiberglass parts, the dash, etc., that had I talked about, would have at least tripled the contents of this website.  In fact, I could have launched a website about what it took to get the BugE into Canada and on the road legally.  All I can say is it was difficult and painful to say the least.  I can certainly understand why there are few homebuilt vehicles on the road in Canada.

This was a great project and likely the most gratifying one I have ever attempted.  I am completely sold on EV technology as a result of this experience and in driving the Lithium BugE.  It seems pretty amazing to drive hundreds of kilometers and not see the impact to my electricity bill.  The operating costs are negligible.   The Lithium BugE is not an entirely practical vehicle however.  It may not even be as practical as a motorcycle because of its less than stellar suspension system.  Nevertheless, it is a lot of fun to drive and draws a lot of attention.  I really like the impact it has on people.  Their expressions are funny to say the least.  The overwhelming majority of people smile and are excited and very interested in the vehicle.  It does create awareness and likely fosters peoples hopes and beliefs that EVs can become a reality with advantages, not compromises.  I have had a lot of people comment that they are surprised how fast the Lithium BugE is.  When I tell them the range, they are equally surprised.   When I tell them that this vehicle gets the equivalent of 400 to 600 mpg, I'm not sure if most of them believe me.  I can tell they are thinking of the possibilities in their minds. 

This project did exactly what I was hoping for and through the course of the research I did and in building the Lithium BugE, I believe I am now qualified to build a fully practical EV.  Or at least I am a lot more qualified than I was before I started this project!  I'll take some time off to enjoy the Lithium BugE but I have already begun preliminary research into my next EV.  If I could buy the Aptera and import it into Canada, I would prefer to do that. The Aptera is a purpose built EV with amazing specifications and is slated to be available this year (2008) in California.  It is a radical leap and likely 20 years ahead of its time.  It is unlikely that we will see an Aptera in Canada for many years if ever.  Assuming I would not be able to obtain one, my next EV may look suspiciously familiar or at least be influenced by the Aptera.

For questions about the Lithium BugE, please contact me at nap@nappepin.com

Thanks.

Nap Pepin

Frequently Asked questions:

• Did you design the BMS entirely yourself?
  Answer - Yes, I designed the circuits, designed the PC boards and I wrote the software.  It was a difficult process but a lot of fun too.

• Will you send me your design?
  Answer - No.  I spent a huge amount of time doing the research and designing the system.

• There are a couple of Battery Management Systems available including one from Thunder Sky.  Why did you not purchase one of those?
  Answer - None of them met my requirements.  I wanted something that was fully expandable, provided data to a terminal and LCD and also provided driving information.  As well, I had my own ideas around how lithiums should be charged and wanted the flexibility to change or add functionality.

• Would you ever drive the BugE on a highway?
  Answer - No, it is meant for slower speeds on smooth roads.  The frame is not much more elaborate than a good go-kart.  I may build a much better frame with a full suspension system and disc brakes.

• Isn't the BugE unsafe?
  Answer - It's about as safe or perhaps even less so than a motorcycle because that is approximately what it is.  It is very visible with the extended faring so that could make it safer, sometimes. 

• What did you think of the Thunder Sky batteries?
  Answer - Their rated capacity is about what the manufacturer states.  However their ability to deliver high currents diminishes as the cells are depleted.  For example, when the Lithium BugE is fully charged, the battery pack can deliver 300 amps.  This remains until the pack is about 35% depleted.  After that, you are in danger of having a cell fall below 2.5 volts if you try to draw that much current.  I don't really notice it when I am driving normally.  In fact, I may limit the controller current to about 180 amps so that the performance is more consistent throughout the discharge cycle.

• Are the Thunder Sky batteries under warranty?  
  Answer - They are supposed to be but I really don't think they are and am not counting on it.  I assumed I bought them without a warranty.

• Would you recommend the stock BugE?
  Answer - Yes and no.  I would recommend it for a gated community or around a neighborhood with good roads, slower speeds and where there is not a lot of vehicles.  

Updates

I thought I would start a log file to provide updates on developments, changes to the Lithium BugE and even driving experiences.

January 13, 2010 - The Lithium BugE has been donated to the Reynolds Alberta Museum who asked if I would consider donating it when I was finished my testing.  I decided to do that since it would be such an honor to have it in the world class museum.  The process required that the vehicle be appraised.  After the appraisal, I would receive a tax deductible receipt and be able to claim 50% of the amount.  As it turned out, the vehicle appraised at $24,000 which I was very satisfied with.  My final costs were over $17,000 in Canadian funds.  I had put about 4000km on the vehicle and had a lot of fun driving it.  The museum plans to demo the vehicle once in a while.  To help ensure the longevity of the lithium cells, I am putting together a current source external charger that will work with my BMS to ensure the cells remain changed and perfectly balanced.  I addition, I'll be replacing 1 bad cell that had failed on me.  Not bad to have only 1 bad cell out of 24!  I am already building the next vehicle, a tandem 2 seater with 3 wheels again.  This will be much more advanced, fully enclosed and much safer including the front and side impact air bags.  The fame is being built in the US right now.  This vehicle will use cells that are of the same quality that will be used by the major car companies.  Hopefully I will achieve a range of 400 to 500 km.  This is the last entry for this website.  So long Lithium BugE, Nap Pepin

August 2, 2008 - I have driven the Lithium BugE close to 2500 km with no major problems.  I made major programming changes to the motor controller to limit the current at higher RPMs.  I was finding that the vehicle had too much torque at higher speeds making it a jittery ride, especially when going over a bump in the road.  In addition, I was experiencing low cell voltage warnings when I accelerated hard and the battery charge was less than about 70%.  The Thunder Sky batteries cannot provide the 330Amps or so that the Lithium BugE demands constantly through the discharge curve of the batteries.  To resolve this, I adjusted the controllers power limiting map so that torque is tapered off starting at 2500 RPM.  Basically, in 500 RPM segments after 2500 RPM, the power is limited to 70% then 65% then 60%.  So far, I do not receive a low cell warning as far down as 50% of the battery charge.  That is as far as I have tested it to date.  The low cell warning occurs as a text message "Low Cell Warning"  on the in dash LCD display.  The BMS reports any cell that has dropped to 2.8 volts or less.  The performance impacts are fantastic in my opinion.  The initial acceleration is still brisk but now the torque tapers off just like a car and is extremely smooth and stable as speeds of 40kph and up are reached.  It feels very refined now.  Clearly I cannot accelerate from 0 to 60mph in < 7 seconds anymore but it is more important to have consistent performance and control that is stable, smooth and safe.  In my opinion, the 90Ah Thunder Sky batteries and likely all Thunder sky batteries should only be rated for 1.5 C.  You can draw more for short bursts of perhaps 5 seconds but that is about it.  If I find that I do receive any low cell warnings at low states of charge, I'll make further adjustments.  I still have some room because the Lithium BugE  is very fast even with these changes.

August 3, 2008 - I have made additional adjustments to the motor controller parameters  to refine the regenerative braking.  With these changes, the variable regenerative braking is more refined, smoother and so responsive that it will be rare for me to use the mechanical brakes.  These changes will result in more recovered energy and a bit more practical range which by the way, I still have not tested.  What I can say about the range is that I drive for 1 to 2 hours at a time and come back with 50% to 70% charge remaining.

At this point I am reliant on the Curtis Controller's battery state of charge indicator as mine is not accurate as of yet.  I wrote the code such that I take voltage samples of the battery back when drawing more than 10 amps.  This is greatly flawed because of the significant voltage sag that occurs when accelerating hard.  I  need to come up with an algorithm that evaluates voltage deltas to determine state of charge.  

August 3, 2008 - I want to start on the next EV project soon however I am planning to try to find one or more corporate sponsors to fund the project.  If I am successful at obtaining some A123 cells, I am guessing that my battery costs alone will be $30,000.  Maybe I need to stick with off the shelf Thunder Sky batteries and just try to work within their limitations.  The key is to design around a battery pack with the highest system voltage as possible and likely in the range of 300 volts.  Adding super capacitors for acceleration bursts is another possibility but implementing them is difficult and complex.  The strategy behind this next project is to use composites to achieve a super strong but very light vehicle.

September 20, 2008 - This past 6 weeks has been very busy for me, mainly because of the publicity I received have been on the front page of the Edmonton Journal on June 28th.  Since then, I have completed a 1 day video session with ACCESS TV for a new show called Trail Blazers, am in the middle of another project for the Northern Alberta Institute of Technology (in which  I am a graduate) and on Thursday, September 25th, I will be doing an all day film project with the Discovery Channel.  It is thrilling and a true honor for the media to have taken such interest in the Lithium BugE.  In addition to the above, the Alberta Reynolds Museum (a truly world class transportation museum) has contacted me about acquiring my BugE.

With the weather getting colder, I have tried to drive the Lithium BugE as much as I can and have now driven about 3400 km.  Last Thursday and Friday I drove it to work so that many interested colleagues could see the Lithium BugE but also to perform tests in rush hour traffic conditions.  As expected, the range is greatly reduced when traveling  at highway speeds.  In addition to shortened range, the cells go out of balance to a larger degree, so much so that I will have to compensate for the greater imbalances with a modified balancing routine when recharging.   It's and easy software fix.  The range is quite possibly less than 60 miles under high speed conditions or conditions requiring lots of fast stops and starts.  Most of the losses in efficiency are due to the less than stellar aerodynamics caused by the open faring.  Still, I do the math and see that in such conditions, it still achieves an equivalent fuel economy of about 400 mpg.  My next vehicle will focus not just on low vehicle mass, but also aerodynamic design so that at higher speeds, the absolute best efficiency is achieved.  I know the speed to power consumption relationship is normally that with twice the speed, the energy consumption is cubed.  What is not clear to me (yet) is if that is fixed.  I'm guessing it isn't and with superior aerodynamics, high efficiency can still be obtained at higher speeds.  I certainly would not recommend the BugE for driving on a highway and I don't think it was intended for such speeds.  It was designed for high efficiency commuting at speeds of 50 to 70 kph and it does that extremely well.

Back

Home