How to avoid high current peak draining the coin cell battery life?

Many of you (us included) have probably experienced issues with high peak currents when working with coin cell batteries in IoT projects. The high current peak and coin cell battery life don’t go hand in hand, most commonly, killing the battery. This is a quite annoying problem and one starts questioning whether this could be prevented somehow?

Our CPO, Björn, gives three practices to consider before picking the coin cell battery for your next Internet of Things project:

#1 Do you really need a coin cell battery?

If your form factor could allow for a bigger size, an alkaline AAAA battery might handle the peak current much better. Of course, there are other things to consider then, for example, the battery behavior in high/low temperatures. As always, the approach of picking the right energy source needs to consider the complete use case.

#2 Get your device’s current consumption as low as possible!

Yes, it may sound obvious, yet there are many pitfalls to be avoided. For example, try to avoid different parts of your device being active at the same time, hence creating higher peaks. This is common during radio transmissions, so consider well if you should have some other things out of sync or sleeping at that time.

#3 Add a capacitor (in parallel) with the battery!

It works, but how much to add depends on each case and needs to be tested out. After browsing countless forums and articles with also countless different opinions about this, Björn decided to do some extensive testing.

Find the test results on six different set-ups with following capacitors

• 2x100uF 16V MLCC, C1210C107M4PAC7800 from Kemet
• 470uF 16V aluminium capacitor, UWT1C471MNL1GS from Nichicon

using Otii Arc and Otii Battery Toolbox, as well as the deeper technical discussion in the tech paper published at Design Spark in the link here.

There are solutions to the high current peak and coin cell battery life, but they require a low power mindset and testing. So #measureeverydamnday and as always: let us know what you think and reach out if you have questions.