Elenco XP&trade - Manual (Page 55)

Project B23 Battery Tester (4V or less)
This project is similar to the preceding Digital Voltmeter project, but
tests batteries. Modify the preceding circuit to be as shown here.
Turn on the slide switch (S1). Load program Battery Tester into the
microcontroller (U21) using the programming instructions in project
B1. Press the F8 key to open a Terminal as described in the Digital
Voltmeter project.
To test a battery, hold the battery in the position shown, then push
the press switch (S2) to measure and display the voltage. Hold the
battery with negative (–) terminal resting on the 7-snap wire and
the positive (+) terminal touching the end of the red jumper wire. If
measurement is 0.0V or 0.1V, then you are not making proper
contact with the battery terminals, or have the battery upside down.
For 1.5V batteries, if measurement is 1.0V or less, then the battery
is dead and no longer useful. Batteries up to 4.0V can be
measured.
Part B: This circuit uses the 100
Ω
resistor (R1) as a “load”, to make
sure the battery works properly when current is being drawn from
it. Remove R1 from the circuit and re-test some batteries. The
measured voltage may be higher now; the difference will be slight
for batteries that are new or of high quality, and higher for batteries
that are older or of lower quality. You can use this test to compare
different battery brands.
You can also replace R1 with the motor (“+” on right) and fan. This
makes the “load” heavier, and the measured voltage for a battery
will be lower.
Optional:
!
WARNING: Moving parts.
Do not touch the fan or
motor during operation. Do
not lean over the motor.
-54-
A battery make electricity using a
chemical reaction, but has a
limited amount of chemicals and
not all of it can react at the same
time. When a battery cannot
supply as much current as a circuit
needs, the voltage (electrical
pressure) drops.
Engineers refer to this as putting a
load on a battery, because it is the
burden the battery is carrying.
+
–