Here are the results of measuring my current sense resistor, R1.
Here's my measurement setup and results:
? ohms 48.3 ohms
o----------R1---------o----------R2----------o
0V 21.7 mV 16.68 V
Total ohms 48.5
The 48.5 total ohms reading was fluctuating between 48.5 and 48.4.
The R2 ohms fluctuated between 48.3 and 48.4. My guess is the total
is actually 48.45 ohms.
Total current through R1 and R2 is
I = E/R = 16.68 V / 48.45 = 0.3443 amps
so:
R1 = E/I = 21.7 mV / 0.3443 amps = 0.0631 ohms
Interesting, more current out than I expected for that little
battery. Here's a spec sheet:
http://www.apexbattery.com/wal-mart-es4lbs-motorcycle-battery-
motorcycle-batteries-wal-mart-motorcycle-batteries.html
http://tinyurl.com/mw5ehj
It shows "CCA" as 45. Cold cranking amps (CCA) is a measurement of
the number of amps a battery can deliver at 0 ° F for 30 seconds and
not drop below 7.2 volts. I guess since the temperature was 70 F, it
could deliver a lot more. Glad I taped a plastic shield over the top
of the battery.
I updated the experiment report to reflect the new values:
http://www.mtaonline.net/~hheffner/HullMotor.pdf
Best regards,
Horace Heffner
http://www.mtaonline.net/~hheffner/
