An eGas Gauge for my eBike

Soldering iron (generic)

Toggle Switch, DPDT

2.2 uF 16V electrolytic

Battery Holder, AA x 3

Capacitor 10 nF

Arduino IDE

3.9K 0.1W 5%

ATtiny85

Resistor 10k ohm

My Lectric XP eBike displays battery voltage as an indicator of remaining energy. When the current is zero, this strategy works fairly well. But when riding, the voltage varies as a function of current. A better way to estimate this energy is to keep track of the ampere-hours drawn from the battery. The first time I fully charge up my battery and then discharge it to what I call empty, the circuit learns this change in ampere-hours. From then on, I fully charge my battery, tell the eGas Gauge it is full, and system tells me the remaining energy. There are three output options. It can beep out the data within +/- 3%, drive an analog meter for continuous readout, or flash an LED to indicate Full, 3/4, 1/2, 1/4, or Empty. Complete details plus code are available <a href="https://rick.sparber.org/eBikeGauge.pdf">here</a>.

An eGas Gauge for my eBike

This ATtiny85 based system measures ampere-hours to determine the remaining energy in my bike's battery.