IPRO 304 Spring Accomplishments

• Spring 2004 Team Members

• Project Description

• Individual Team Accomplishments

  • Battery Team

  • Fuel Cell Team

  • Design Team
    

• Conclusions and Future Work

• Original Fuel Cell Schematic

• Spring 2004 Final Presentation

The following are excerpts from Spring 2004 Final Report which can be viewed by clicking here.

The purpose of this IPRO is to create a hybrid electric vehicle capable of traveling from Chicago to Milwaukee. The vehicle is to be comprised of the following components. First the base of the vehicle is an electric wheel chair designed by Invacare for outdoor use. The second component was the Li-ion batteries with a passive cooling system. This passive cooling system employs a phase change material to keep the operating temperature of the batteries as low as possible. Next, to charge the batteries, a fuel cell is the third component of our vehicle. It was donated to us by Avista labs and it is designed to be used as a 500W 48V battery charger.

The vehicle is designed to run on four Li-ion cells to operate and have four in reserve being charged by the fuel cell. When one battery bank goes dead the user can then switch to the new set of batteries fully charged by the fuel cell and allow the discharged set to be charged.

The batteries constructed by the group are extremely successful. They are able to power the wheel chair under all conditions tested. We did have some troubles with the current design of the output terminals. The connectors used are slightly smaller than the ones on the vehicle causing them to occasionally come free during operation of the vehicle. Additional testing demonstrated that the passive cooling system did lower the operating temperature of the batteries. See the results of data acquisition section for further information.

Two small hydrogen tanks will be attached to the fuel cell at one time. From our tests we are confident that each set of two tanks will last at least four hours. Therefore during the journey to Milwaukee we plan to coordinate the breaks for food and rest every four hours at which time the hydrogen tanks will be changed. From this estimate we ordered ten small tanks for the trip. See below polarization curve:

The results of the design group were mixed at best. The trailer successfully carries both the fuel cell and the hydrogen cylinders securely and safely. However, the pins used to support the trailer keep bending and need to be replaced. Also, the seat wobbles quite a bit on the support. This is due to the fact that only one bolt holds the seat in place, and no locking mechanism was placed at the end of this. Also, the seat cover is difficult to remove and replace, and it must be removed to tighten the seat it because the seat cannot be tightened by hand easily. On the positive side, the equipment was sturdy enough to take the bad treatment that would be encountered driving from Chicago to Milwaukee. In addition, the new equipment was light enough so that there was little power drain on the system. This is a positive result in order to extend the life of the battery pack on one cycle.

One possible way to avoid the problems of the weak support pins would be to attach stroller wheels or the equivalent to the front pegs on the cart. This would allow for stabilization of the cart and better handling. The design group initially attempted to acquire the stroller wheels for this project, but none were available at the time and none were sold separately form their respective stroller. Also, the supports in the front of the cart may not be able to withstand the forces that would act on them.

Another result of the testing was the very large turn radius required to run the system smoothly, this is necessary because the back wheel of the vehicle rubs against the cart and can cause the vehicle not to move. Extending the handlebars of the cart can avert this problem, but it has not been tested. However, this makes the system difficult to drive.

Other aspects that have not been considered, as of yet, which include that the placement of the battery packs on the floor is temporary, and will be repositioned for the final run. There will be a structure built to hold all eight batteries but that will still keep some floor space open. This design must be easily accessible for frequent testing of the connections and battery operation.

Finally, the fuel cell has not been connected to the batteries. This will be done and may result in alterations to the design. For example, the handlebars may be shortened so that less wiring is necessary and so that the wires will not drag or snag on anything. The wires may also be fed through a rubber tube to keep them safe and to prevent any damage. Again, this may change the overall design slightly. However, the initial design should not change dramatically.

While the initial vehicle testing was very promising considerable amounts of work remain for the following IPRO groups. As documented in the individual group sections above each group had certain flaws in their design discovered once the vehicle was operated. The major ones include finding a more effective method for hooking the batteries to the vehicle. The distance between the vehicle and the trailer is two small and needs to be extended to allow for smaller turning radiuses. Also, the attachment between the trailer and the wheelchair needs to be improved to prevent bending of the pins. Finally a charger circuit needs to be perfected in order to implement the fuel cell as a battery charger. Once these are completed it will be possible to do testing over long distances allowing the batters to be completely discharged and then recharged by the fuel cell.

The next important step in the project will then be to “hybridize” the vehicle. Using the fuel cell to power the vehicle under constant conditions and using the batteries to provide power when variable power is needed. This will further explore the feasibility of using the Li ion batteries with the passive cooling system in hybrid electric vehicle applications.