# US 5,705,912 A · Circuit for preventing overdischarge of rechargeable battery pack consisting of a plurality of rechargeable batteries > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,705,912 A - Document ID: US5705912A - Status: Granted - Kind: A - Application number: 08/307,154 - Filed: 1994-09-16 - Granted: 1998-01-06 - Earliest claimed: 1993-09-17 - Assignees: NEC Corporation - Inventors: Masaki Ichihara - Web page: https://patentgrep.com/patent/US5705912A ## CPC - H01M 10/44: Methods for charging or discharging (circuits for charging H02J7/00) - G01R 31/396: Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery - H02J 7/56: Active balancing, e.g. using capacitor-based, inductor-based or DC-DC converters - H02J 7/61: against overcharge - H02J 7/63: against overdischarge - Y02E 60/10: Energy storage using batteries - Y02P 70/50: Manufacturing or production processes characterised by the final manufactured product - H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY - G01R: MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES (indicating correct tuning of resonant circuits H03J3/12) - H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY - Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION - Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS ## Abstract A rechargable battery pack is constituted by not connecting all of the terminals of a plurality of secondary batteries but extracting them outside. A charging circuit is constituted by a dedicated charging circuit which comprises a constant-voltage circuit and a constant-current circuit for each of the rechargable batteries to charge each rechargable battery separately. A discharging circuit comprises, for each of the rechargable batteries, a controler for preventing an overdischarge and a worning portion for warning of an overdischarge. ## Claims ### Claim 1 A system for preventing overdischarge of rechargeable batteries, comprising: a battery pack having rechargeable batteries, wherein each of said batteries, within said battery pack, is free of an electrical connection with any other one of said batteries, said batteries each having respective terminals thereof connected to corresponding external terminals of said battery pack; and a discharging circuit for connecting with said external terminals to connect said batteries of said battery pack in series with a load, and including voltage detectors, each of which monitors a respective battery voltage of a corresponding one of said batteries, and each of which provides, when said respective battery voltage indicates overdischarge, an overdischarge detection signal to a controller which responds to said overdischarge detection signal by interrupting said connection of said batteries with said load. ### Claim 2 (depends on 1) The system of claim 1, wherein said controller interrupts said connection of said batteries with said load by providing a control signal to a switch, and said switch opens said connection in response to said control signal. ### Claim 3 (depends on 2) The system of claim 2, further comprising means for generating an alarm signal in response to said control signal. ### Claim 4 (depends on 3) The system of claim 3, wherein said alarm signal is a sound. ### Claim 5 A system for preventing overdischarge of rechargeable batteries, comprising: rechargeable batteries disposed in a battery pack, each of said batteries having a respective positive and a respective negative terminal, each said positive and each said negative terminal being electrically connected to a respective exterior terminal of said battery pack, and being free of any electrical connection with any other said positive and said negative terminal; and a discharging circuit connecting with said external terminals to connect said batteries of said battery pack in series with a load, and including voltage detectors, each of which monitors a respective battery voltage of a corresponding one of said batteries, and, when said respective battery voltage indicates overdischarge, directs said discharging circuit to stop discharging said corresponding one of said batteries. ### Claim 6 A system for controlling discharge and recharge of batteries, comprising: a battery pack having external terminals, and containing said batteries, each of said batteries having respective battery terminals, each of said terminals being coupled only to one of said external terminals of said battery pack; a discharger comprising, for each of said batteries, a respective overdischarge detector circuit, and being removably coupled with said external terminals to form a series connection between said batteries and a load; and a charger comprising, for each of said batteries, a respective recharge circuit, and being removably coupled with said external terminals to form a respective dedicated connection between each of said batteries and said respective recharge circuit; wherein said discharger is coupled with said external terminals during said discharge of said batteries, and said charger is coupled with said external terminals during said recharge of said batteries. ### Claim 7 (depends on 6) The system of claim 6, wherein: each said overdischarge detector circuit monitors a respective battery voltage of a corresponding one of said batteries, and provides, when said respective battery voltage indicates overdischarge, an overdischarge detection signal to a controller to interrupt said series connection; and each said recharge circuit includes a respective constant voltage circuit and a respective constant current circuit connected to a power supply. ### Claim 8 (depends on 7) The system of claim 7, wherein said controller interrupts said connection of said external terminals with said load by providing a control signal to a switch, and said switch opens said connection in response to said control signal. ### Claim 9 (depends on 8) The system of claim 8, further comprising means for generating an alarm signal in response to said control signal. ### Claim 10 (depends on 9) The system of claim 9, wherein said alarm signal is a sound.