Objectives/Goals
My objective was to learn about the underlying
chemistries of the lithium ion and lead acid batteries in order to better
understand why their discharge capacities were affected by different temperature
extremes.
I wanted to determine which chemistry would work
best at very low temperatures. I hypothesized that the batteries would lose a
large portion of their energy capacities due to the fact that most chemical
reactions slow with a temperature drop.
Methods/Materials
The primary materials used were two identical lead
acid batteries, A and B, that were both discharged at the same rate at 68 deg.
F. Then, after being simultaneously charged up again, they were both submerged in
35 deg. F ice water for 30 minutes.
The lead acid batteries were then separately
discharged at 35 deg. F, and their voltages were recorded every minute. For the
lithium ion batteries, I contacted a battery testing lab in Philadelphia where
they were able to follow my instructions to duplicate my lead acid testing.
They discharged three lithium ion cells at: 0 deg.
C, 20 deg. C, and 40 deg. C and measured their voltage over time.
Results
The results of my testing proved my hypothesis
correct. Both the lithium ion and lead acid batteries showed a decrease in
their energy capacities as they were discharged in the colder temperatures.
However, what was rather surprising was that the
lead acid battery, as a percentage of its overall capacity, showed less of a
drop than that of the lithium ion. The lithium ion battery is a very useful,
high energy capacity battery that ran longer than the lead acid battery.
But when the lithium battery was subjected to
extreme cold, essentially, it failed to function as a battery whereas the lead
acid showed a nominal drop in its energy capacity.
Conclusions/Discussion
In conclusion, though a lithium ion battery is a
very light weight, high energy density battery that is commonly used, in a cold
temperature, its energy capacity droped severely. However, the lead acid battery,
a heavy and toxic battery with a low energy density, proved more efficient
during cold temperatures.
This project shows great social implications because
primarily, most everything we depend upon today is battery powered. With the
knowledge of what might affect the performance of a battery, such as
temperature, certain precautions may be taken by battery companies in order to
enhance their products.
Project Summary
My project explores the effect of varying
temperature extremes on the relative energy capacities of lithium ion and lead
acid batteries as measured by their voltage drop over time when subjected to a constant,
resistive load.
Project by Sarah J. Adams
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