Does Warmer External Temperature Translate Into Further Distance in an Electric Rickshaw
By. Stephon Glover

Target Problem

Electric Rickshaw’s are a common form of transportation in throughout Asia. There are no manufacturer recommendations with regard to temperature and distance.

Problem Statement: The use of Rickshaw’s in Beijing is invaluable. They are used as small vehicles for families, as taxis for 1 or 2 people, and as a means of getting around smaller districts of the megacity. There is a noticeable drop in not only distance but also torque when temperatures drop below 15 degrees Celsius. The following experiment will address the issue of temperature variation and the effect it has on the speed and distance travelled of an electric Rickshaw. The results of this study can be used in the design of electric battery storage and insulation.

Literature Review
There are numerous tips to improve electric vehicle performance, namely altering the way the vehicle is used. There is little language in the way of battery insulation, which will be the method used in this experiment.

Of note, SAE International (2011) concluded that tested energy consumption varies based on driving ability and duties performed by the vehicle, such as heating and advanced audio systems. Electric vehicle performance is dictated not just by temperature, but deteriorates substantially based off of nonessential features.

Official reports on the charging and battery efficiency of the EV during the test period to present a total plug-to-wheel EV efficiency when operated over both regulated and real world drive cycles (Cenex 2012).

For this experiment, the vehicle will be operated under normal conditions, then the temperature of the battery will be altered using towels and a rubber water bottle. The vehicle to be used during the experiments provides basic transportation. The distance, as well as the speed at which it was traveled will be measured across two days, three times each day.

Experimental Design Steps and Sequence of Events
Day one:
The Rickshaw will be charged and driven 5.5 kilometers, three times each day. In between trips fill or remove fresh hot water bottle from battery compartment. The time it takes for compartment to warm or cool is inconsequential, only that the temperature is within variable range. 1. Ensuring a fully charged battery, take the temperature inside battery compartment, and drive set distance. 2. Take temperature and recharge battery. Wrap hot water bottle inside towel and place inside battery compartment. Take temperature inside compartment ensuring that it is at least 5 degrees higher than on previous trip. Drive set distance. 3. Take temperature and recharge battery. Wrap hot water bottle inside towel and place inside battery compartment. Take temperature inside compartment ensuring that it is at least 10 degrees higher than on previous trip. 4. Take temperature once third trip has concluded.

Day one notes: Temperature dropped significantly during test that included water bottle, however performance did not drop. Took longer to warm compartment than expected. Water bottle is lukewarm to touch, whereas it required being carried with a towel when first filled.

Day two 1. Ensure battery is fully charged, as temperature drops overnight will possibly reduce battery charge. Take temperature; wrap hot water bottle inside towel and place inside battery compartment. Take compartment temperature, ensuring that temperature is at least 10 degrees higher than initial reading. Drive set distance 2. Take temperature inside the compartment and recharge battery. Wrap hot water bottle inside towel and place inside battery compartment. Take temperature inside the compartment, ensuring that it is at least 5 degrees higher cooler than on previous trip. Drive set distance. 3. Take temperature and recharge battery. Remove hot water bottle and towel. Take temperature outside of the battery compartment, and also inside the battery compartment then compare to first experimental reading. Temperature should reflect this within a plus or minus 1-degree differential. Perform final drive.

Day two notes: performing the test in reverse is easier as the compartment cools itself off between drives. Noticed better acceleration on final drive than on first experimental drive. Attributed this to the battery being “warmed up” from previous drives and charges. Overall length of time ended the same, with significant drop off performance three-quarters of the way through the test.

Reasoning
It has already been established that cold weather has a negative effect on the range of electric vehicles. Varying the temperatures will help determine at what point performance drops. Running the test with an unchanged variable will help determine a base level of performance. Switching the order of test will also remove the variable from performance, since on day one the temperature will be increased while on day two it will be decreased.

Tools and Tech
Generic electric Rickshaw (Tuk Tuk)
800W, 48v Battery
10X7 inch Rubber Hot Water Bottle
27X52 inch cotton bath towel
Generic thermometer
Mapmyrun GPS tracking software

Variables
Independent variable: temperature inside battery compartment
Dependent variable: the time it takes to drive 5.5 km
Controlled Variables: Distance travelled, battery charge, path taken on each test.

Reducing the likelihood of confirmation bias.
Taking the same route for each test ensures that any variation in results will be solely based on battery compartment temperature. Taking the same route ensures that the exact same distance will be travelled and accounts for unseen variables such as traffic and elevation. Making sure the battery is fully charged before each test will ensure that power output remains constant throughout the experiment. By running the experiment across two days with the same variables, the experiment assures the results will be based solely on the independent variable. By changing the order of the temperature variables and attempting to recreate the results, the experiment will eliminate any unforeseen variables.

Hypothesis
The hypothesis is that even a slight increase in battery compartment temperature, will result in noticeably better performance. This hypothesis is based off of the SAE International study, as well as common knowledge that electronics show a dip in battery life during cold weather.

Process of Data Collection

As previously stated, the battery with the warmest temperature had the fastest time across both days. What was interesting about the results is how drastically the pace improved. The pace dropped with the temperature, as expected, but it never increased back to the original levels. What is interesting is during the final test run, without a temperature variable, performance was still within the independent variable ranges. Acceleration also improved with temperatures. The colder the temperature, the longer it took for the Rickshaw to reach its top speed of 40 kilometers per hour. This speed is manufacture claim and was never actually achieved. The pace set throughout the experiments, leads to an average of 33.95 kilometers per hour. Given mitigating factors such as path, minute elevation and acceleration this is considered a reasonable variable.

Route Taken

Data Table: Speed as influenced by temperature Name | Temperature(Celsius) | Duration | Pace (Minutes) | Speed (KPM) | Day 1: Test 1 | 8 Degrees | 0:11:19 | 2:03 | 29.27 | Day 1: Test 2 | 15 Degrees | 0:09:47 | 1:46 | 33.85 | Day 1: Test 3 | 26 Degrees | 0:09:12 | 1:39 | 36 | Day 2: Test 1 | 19 Degrees | 0:08:49 | 1:35 | 37.57 | Day 2: Test 2 | 13 Degrees | 0:09:36 | 1:44 | 34.5 | Day 2: Test 3 | 9 Degrees | 0:10:11 | 1:50 | 32.52 |

Appropriate Methods
The fact that the warmest temperature produces the fastest time proves that this distance and route were good metrics to measure the effects of temperature on range. One issue of note is the time it took to cool between drives on the second day. This could be an issue of internal temperature, something that cannot be measured without making the battery unusable. But dropping the temperature resulted in the same change in performance as increasing temperature, even after repeat test and charging, so these metrics are appropriate for determining the influence temperature has on performance. Allowing more time between each test may be used to draw further distance between each independent variable.

Results

Time taken to complete test route (in minutes)
As presented by the chart above, each test registered a different time, but there is a clear correlation between temperature and performance. The standout time of the initial test further confirms the results of the test. This run was done at just 1 degree cooler than the final test, but finished over a minute later. From the second test and through out the remainder of the experiment, regulating the temperature produced improved performance.

Conclusion

Confirmation of Hypothesis
The results gathered throughout the experiment and presented confirm the hypothesis that increasing the temperature surrounding the battery will improve performance. While the original equipment manufacturers claimed 40 kilometers per hour was never achieved, it is possible that further increasing the temperature in the battery compartment would allow that number to be reached.

The principles of credibility and accuracy are fundamental cornerstones of the scientific method.

Experimental Design as a Key Factor
Following a set path when implementing the experimental design is a crucial step of internal validity. Even with accurate results, messy or erratic design will compromise the strength of the experiment. Internal validity and authenticity serve as the foundation of any experimental design. A properly design experiment should only have one independent variable for testing. If, for example, the thermometer was changed on the second day, there would be no way of knowing if the readings were correct. This would call into question the initial results. This would also cloud the objective of testing. The experiment facilitator must be able to determine the cause and effect of the independent variable. Every other factor must be controlled, even if scale must be reduced.

Replication
This experiment can be replicated using any variation of tools, distances or procedures. The vital components that will determine whether the results have been successfully and accurately reproduced are listed below.

Insufficient battery life can hamper both acceleration and top speed, which will render any recorded metrics useless.
Temperature control is the independent variable. Allowing enough time to pass when testing the effects of reduce temperature will ensure that residual internal temperatures will drop as well.
Setting one path to follow throughout each of the experimental test is key. This removes possible variations in elevation, and slight differences in distance.
Using the same tools throughout the experiment. Changing tools one the experiment has started will also negate any previous readings. It is important to test each tool for accuracy and reliability before initiating any formal test.
One driver is an unacknowledged variable that the previously mentioned SAE International study took into account. While this experiment does not use the advanced tolls and methods used during that study, it is important to maintain scientific integrity no matter what.

Evaluation of Validity
Putting the pieces together is the final step to achieve a high standard of validity.
In order to substantiate the quality of being factually sound, this experiment would need to be replicated by either the original facilitator or an independent party. This is arguably the most important step, as without reproduction of the experiments, it is just raw data. Replicating the results of the experiment derives information that can then be studied further to gain insight and knowledge. As it stands now, the experiment is just a study that has not been reviewed and is not valid. The experiment must be recreated under the same specific steps in order to accurately replicate the results.
References

Edgebander Machines (2007) Phoenix Battery powered Tuk Tuk. Retrieved from Link

Lincoln Repository (2012, December) Electric Vehicle Efficiency Mapping (pp. 133-122. ISBN 9780857094568) Retrieved from Link

SAE International (2011, May) UK Electric Vehicle Range Testing and Efficiency Maps (Publication number 2011-39-7224) Retrieved from Link