An ultra low current low cost zinc-air battery discharge monitor utilizing a microcontroller based countdown algorithm

The design and testing of a low cost ultra low power microcontroller based zinc-air battery charge monitor is presented. The zinc-air battery chemistry is a lightweight and efficient portable energy solution that features an extremely flat voltage profile as the battery discharges. This design provides an alternative charge monitoring method to a voltage sampling system. The circuit operates by sampling the outgoing current and performing a count down algorithm. This design utilizes an ultra low loss resistive current sensor and a microcontroller to sample the outgoing current of a zinc-air battery in a fully programmable interval that defaults to two seconds. The circuit shuts down into a sleep mode when not sampling, which draws about 8μA from the 12V battery. The average current is 22μA. This current will discharge the battery by 1% in approximately 1.54 years. Overall cost is US$7.00 using bulk consumer parts. The paper presents design goals, considerations, and hardware results of the circuit.