Due 4pm Tuesday, Jan. 16, on web site
Reading Material
Handouts from class. Natcar rules (follow links from class website to natcar site) &
take a look around at websites of other schools.
Optional Additional Reading
General Information - H&H on batteries (930-940)
To learn about charging NiCd cells, go to
http://www.panasonic.com/industrial_oem/battery/battery_oem/chem/niccad/niccad.htm then
click on the charging link (~14 pgs).
In the Lab
Generate discharge curves. Nominal current for discharge for each group will be
determined in class. For the discharge, use a constant resistance (much easier than
constant current, and the results are similar enough for our purposes). Be careful,
the "resistor" will get real hot, especially at the higher currents. Take enough
voltage data points to see the shape of the curve. Use a stopwatch or other timer to
get the timing correct. End the discharge at .8-1 V per cell (higer cutoff voltage
for lower discharge rates), or 4.8 -6 V per battery. Make sure you record which
battery the curve is for, and that the batteries are fully charged when you start.
After recharging, repeat the discharge but stop at 100% capacity, 50% capacity, and ~10% capacity to sketch oscilloscope traces of the battery voltage when driving a motor using pwm. Pick a PWM duty cycle of 25% (ie: 1ms on, 3ms off). Feel free to experiment with PWM frequency. Last year at Berkeley we used 200 Hz.
Deliverables
Brief summary of results with sketches of scope traces up on website. Scanned in is
fine. I'll work on trying to get us a way to translate scope traces directly to the
computer, so if anyone has any suggestions...