Testing battery powered devices

Battery powered devices present unique test challenges. During development, a circuit may be powered from a fixed power supply to eliminate the variability and hassle of debugging with a battery. However, this does not reflect the real environment the circuit will operate in. As a battery discharges its voltage decreases following a battery specific curve until at some point the battery is exhausted and its output voltage collapses. Eventually the device will have to be tested in its real-world environment.

Testing a devices behavior as the battery discharges can be time consuming and make reproduction of any failures difficult. A better approach would be to simulate the battery discharge curve over a shorter time period, sufficiently long to allow the device to experience and react to the shifting voltage and short enough that the test can be completed in a reasonable time frame. This allows repeated tests if any failure occurs.

To help with these kinds of problems, Five Wire includes the Waveform Source which is capable of acting as a power supply. Its output can drive voltages between 0 – 5 V with load currents up to 100 mA. It can be configured to generate a fixed output such as +3.3V DC but also includes standard waveforms that simulate battery types such asĀ  Alkaline, Ni-Cad, Li-ion, Ni-MH, and LiPo. The discharge time can be adjusted to 60 seconds, 300 seconds (5 minutes), or longer. Simulating battery operation of your device using the Five Wire Waveform Source allows you to quickly test and debug issues related to battery operation. Here is an example of a LiPo discharge over a 5 minute period using the Waveform Source.

If the battery type or discharge curve you want to test is not directly supported in the menus, you can create your own custom waveform for testing. The Five Wire Waveform Source is an arbitrary waveform generator (AWG). It has 10 bits of vertical resolution, 0 – 5 V output, and each waveform can include up to 1020 points. The time duration of each point is settable with a range from 10 microseconds to 20 seconds for a maximum waveform duration of 20,400 seconds (more than 5 hours). The waveform can be developed using a spreadsheet or using MBScript, a ‘C’ like scripting language included in the Five Wire application software.