Reading the battery from the motors
- Log
- 16 of 25
- Date
- Reading
- 1 min read
Skills in this log
The robot runs on a battery, but nothing tells you how much is left. You find out when it switches off. On the evening of the cable breakdown, I found a way to read it without adding anything.
The idea
A community member had pointed it out: the robot’s motors measure the voltage that feeds them, and report it to whoever asks. They are fed by the battery. Reading that value means reading the battery.
First try: all nine motors answer, between 7.40 and 7.50 volts. The robot was on its charger.
An energy tile
On the small slate next to the robot, a tile now shows:
- “PLUG” above 7.0 volts: the robot is on the charger;
- otherwise, an estimated percentage, from a discharge curve;
- a red alert below 6.20 volts.
On the first evening, the curve came from another robot, measured by a community member. Over the following days I measured my own: that is the post on battery life.
The trap
While charging, the voltage you read is the charger’s, not the battery’s. It says “I am plugged in”, not “I am full”. To know where the battery stands, read it unplugged.
