Resettable state-of-charge indicator for rechargeable batteries

摘要

An improved state-of-charge indicator for a battery wherein the counter circuit of the battery state-of-charge indicator includes a means for both resetting and fine-tuning the counter circuit. The current flowing from the monitored battery is passed through a sensing resistor. The voltage across the resistor is amplified and integrated over time and the result of the integration is stored in a capacitor discharged by a switch whenever a threshold voltage is achieved. The cycle is repeated each time coulomb of capacity is removed from the battery. The counter circuit counts the charge/discharge cycles of the capacitor resulting in a count representative of the amount of energy dissipated and therefore indirectly of the amount of energy remaining in the battery system. In this improvement, both a resetting means and a fine-tuning means are included for the counter circuit when the battery is being recharged. The fine tuning means can be preset to reset the counter circuit upon reaching a predetermined voltage signifying that the battery is fully charged. The fine-tuning means may further comprise a zener diode used with a MOSFET mixer.