Measuring battery life for a portable system is a time-consuming task, and the methods that accelerate battery discharge don’t provide reliable results. In the usual approach, you simply measure elapsed time while operating the product to the point of battery discharge. Running several such systems in parallel obviously gives more data, if you can afford to tie up the lab equipment.
You can try to derive battery life from data-sheet specifications associated with the circuit components, but a calculated value is usually far short of the actual operating time. Current drain specs tend to be conservative for low-power ICs because they are tested with high-speed equipment that cannot easily measure low-supply currents. Unlike many electrical parameters, the battery life in most cases is better specified as a realistic typically than as a guaranteed minimum.
Here this circuit is constructed with IC MAX921 and an analog clock to measure accurate battery drain duration.
Hardware Required
| S.no | Component | Value | Qty |
|---|---|---|---|
| 1. | IC | MAX921 | 1 |
| 2. | MOSFET | VN0300L IRF1 | 1 |
| 3. | Battery | 1.5 volt AA Size | 1 |
| 4. | Capacitor | 0.1uF | 1 |
| 5. | Variable Resistor | 100KΩ | 1 |
| 6. | Analogue Clock | – | 1 |
| 7. | Connecting Wires | – | – |
Circuit Diagram
Construction and Working
As we can see, the main part of the circuit is IC MAX 921 and an analog Quartz clock. Here the analog clock is connected to the battery (1.5 volt AA size) and the -Ve terminal of the clock is connected to the drain terminal of MOSFET. It is controlled by the output of IC MAX 921 and this circuit is powered by the testing battery. When the testing battery dried means there is no output from MAX 921, so the MOSFET drain opened. Hence the analog clock stops at a particular hour, and by observing the clock we can get to know the battery drain range. When the test circuit’s battery voltage falls below a selected threshold, the comparator output swings low and turns off MOSFET, removing power to the clock. The inactive clock then reads the running time, provided you set it to 12:00 before the test.
Applications
Can be used to measure battery life in different portable systems.
