Thames & Kosmos Electronics - Battery tester

Sensors & Detectors
EXPERIMENT 

Battery tester
YOU WILL NEED
  resistors,  Ω
  resistor,  kΩ
  resistor,  kΩ
  red LED
  Transistor module
  short wire bridge
 electronics board
 battery clip
 and additional household
item: 9-volt square battery
HERE’S HOW
1. Assemble your battery tester.
2. Connect the battery.
Does the LED really light up or just
glimmer a little?
If the LED shines brightly, you’re in luck
— it means your battery is still in
excellent shape. Or does it only glimmer
weakly? If so, take that as a warning. It
may mean that the experiments in this
chapter won’t work with that battery.
Or does the LED not light up at all? If
that’s the case, check to be sure that none
of the components are installed wrong, or
whether there’s a wire bridge missing. If
everything looks good, you can be sure
that the cause is a dead battery.
That’s how you can tell whether a battery
still has enough power. Even a battery
fresh from the store might have lost some
of its charge just by sitting around too
long before you bought it.
 WHAT’S HAPPENING?
LED1
T1
+
–
A C
R2  kΩ
R
 Ω
R
 kΩ
R
 Ω
+
–
9V
T1
R 4
470 Ω
R 3
470 Ω
R 1
220 kΩ
R 2
22 kΩ
LED 1