Faster battery discharge and lower energy consumption at low supply voltage

November 22, 2017

We love engaging with our customers – they’re smart, curious and very observant!

We’ve received some comments on our latest video tutorial “Measure current consumption for different battery states of charge”, that we’d like to broaden the discussion on.

How come the battery voltage drop will lead to faster battery discharge?

Since the energy consumption is more or less constant over the supply voltage range when using a DC/DC converter, as in this example, as the battery capacity is used up (resulting in the battery voltage dropping) the current consumption is increasing. This in turn will lead to an even faster discharge as the battery voltage drops further leading to even higher current draw. In short, the battery discharges faster and faster the lower the battery voltage gets. This was what we referenced at the end of the video.

Why is the measured energy consumption lower for lower supply voltage?

As some of you have noticed, the BLE beacon we were using to perform these measurements has an interesting “feature” that makes energy measurement a bit tricky. The beacon transmit interval seems to be timed by an oscillator that is affected by the supply voltage before the DC/DC converter. This results in a slightly lower duty cycle with 2V supply voltage compared to a 3V supply – this will to some extent explain why the measured energy consumption was lower at the lower supply voltage.

If you are interested in having a look at the BLE beacon measurement from this tutorial, download the Otii app HERE and the BLE-beacon project HERE.

Keep on commenting and asking questions on our forum! We are listening!

The Qoitech team

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