This article first appeared on Propwashed. Continue reading here.
There’s an ongoing debate about how deeply you can discharge your battery and what the long-term effects are.
A common method to maintain a safe discharge amount is to use a voltage alarm. In this article, I set out to explain how to set up a reliable alarm and the effects of choosing different set points for that alarm. Fair warning: it isn’t really going to accomplish either of those things. If you use a voltage alarm when you fly, you should read it anyway.
The Experiment
Stressing a battery to the point of failure is useful for container testing, but generally something we all want to avoid—we really want to know the best way to keep our batteries healthy. So, we set out to learn about voltage alarm set points.
The test laid out like this: procure three identical batteries and use them under specific test conditions. Fly one down to 3.5V per cell each time, one to 3.4V, and one all the way to 3.2V. Measure voltage during flight through the flight controller, transmitted by telemetry to my Taranis. Program the Taranis with an audible alarm that selects between these set points based on a switch position. Record flight time, time × throttle %, total voltage, and battery temperature for each flight. Record individual cell voltages, internal resistance, and battery thickness after a rest period. Record this data again after each storage and charge cycle.
Based on what we’ve read, draining to 3.5V in flight should leave a comfortable margin in the battery. Draining all the way to 3.2V in flight causes a significant strain on a battery and uncomfortably nears the “irreparable damage” zone. These end points should provide very different results over time. As the batteries degrade, we should see a rise in internal resistance or measure puffing through battery thickness.
This article first appeared on Propwashed. Continue reading here.