Elenco Green Projects - Manual (Page 30)

5V
Project #31 Battery Load
Battery Load Current Project #32
The battery makes 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. That is why the voltage drops when the switch connects the battery to
the rest of this circuit.
Engineers refer to all the devices a power source is running as the load, because
they are the burden the power source is carrying.
Your M6 meter is a
simple meter, don’t
expect it to be as
accurate as normal
electronic test instru-
ments. 50mA
Move the meter to the new location shown
and set the meter (M6) to the 50mA
setting. Set the slide switch (S5) to position
B and see how high the current is when the
battery is running all these devices.
You may see that the current is very high,
which explains why the battery voltage
dropped in the preceding project. Do you
know which devices need most of the
current? Remove some and see how the
current changes to see if you were right.
Build the circuit and set the meter (M6) to the 5V setting.
Set the slide switch (S5) to position C and read the
battery (B4) voltage when it is not running anything.
Now set the switch to position B and see what happens
to the voltage when everything turns on. If the battery is
already weak, some modules may not start. If you watch
the voltage for a while, you will see it slowly drop as the
battery is discharged. If the battery was already weak,
the voltage will drop faster.
If you remove some of the devices the battery is running
(the LEDs, motor, and hand crank), then the voltage will
not drop as much when the switch is turned on.
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See projects 1 & 3 if you need to recharge the battery (B4).