# US 4,394,741 A · Battery monitoring system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,394,741 A - Document ID: US4394741A - Status: Granted - Kind: A - Application number: 06/208,109 - Filed: 1980-11-18 - Granted: 1983-07-19 - Earliest claimed: 1980-06-28 - Assignees: Lucas Industries Limited - Inventors: Michael W. Lowndes - Web page: https://patentgrep.com/patent/US4394741A ## CPC - B60L 15/2045: {for optimising the use of energy} - B60L 58/15: Preventing overcharging - B60L 58/18: of two or more battery modules - G01R 31/3648: {comprising digital calculation means, e.g. for performing an algorithm} - G01R 31/3835: involving only voltage measurements - H02J 7/94: in response to battery current - G01R 31/006: {on road vehicles, e.g. automobiles or trucks (testing of ignition installations peculiar to internal combustion engines F02P17/00)} - G01R 31/396: Acquisition or processing of data for testing or for monitoring individual cells or groups of cells within a battery - Y02T 10/64: Electric machine technologies in electromobility - Y02T 10/70: Energy storage systems for electromobility, e.g. batteries - Y02T 10/72: Electric energy management in electromobility - Y10S 320/18: Indicator or display - Y10S 320/21: State of charge of battery - Y10S 320/34: Robot, hybrid, recreational or emergency vehicle - B60L: PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES (arrangements or mounting of electrical propulsion units or of plural diverse prime-movers for mutual or common propulsion in vehicles B60K1/00, B60K6/20; arrangements or mounting of electrical gearing in vehicles B60K17/12, B60K17/14; preventing wheel slip by reducing power in rail vehicles B61C15/08; dynamo-electric machines H02K; control or regulation of electric motors H02P); SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES (electric coupling devices combined with mechanical couplings of vehicles B60D1/64; electric heating for vehicles B60H1/00); ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL (control or regulation of electric motors H02P); MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES - 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 - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION - Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS ## Abstract A microprocessor based electric vehicle traction battery monitoring system evaluates the state of charge, interfaces with a traction motor control system, and controls recharging. The state of charge is evaluated during the first part of discharge by integrating the current after compensating it for rate of discharge and during the last part of discharge by dividing the battery into sub-packs and evaluating the state of charge from the lowest sub-pack voltage compensated for polarization voltage. The charge storage capacity is also calculated from the lowest sub-pack voltage. The maximum traction motor current is progressively limited during the last part of discharge. During charging, the charge withdrawn is replaced while progressively reducing the charging current and the battery is then charged at a constant current until the rate of rise of the lowest sub-pack voltage falls below a fixed level. ## Claims ### Claim 1 A battery state of charge evaluator comprising: means responsive to battery voltage for producing a voltage value, means responsive to battery current for producing a current value, means for computing the polarization voltage as a complex function of time and of the current value, the complex function being determined in accordance with characteristics of the battery being evaluated, means for correcting the voltage value to compensate for the polarization voltage, and means for computing the state of charge of the battery as a function of the corrected voltage value, said function being determined in accordance with the characteristics of the battery being evaluated. ### Claim 2 (depends on 1) A battery state of charge evaluator as claimed in claim 1 which further includes a clock and in which the computing means is responsive to the clock and the polarisation voltage is computed as a function of current variation with time during a previous predetermined period. ### Claim 3 (depends on 1, 2) A state of charge evaluator as claimed in claim 1 or claim 2 in which the determining means determines the state of charge from the corrected voltage value only when the current value lies within a predetermined range. ### Claim 4 (depends on 1) A state of charge evaluator as claimed in claim 1 which comprises a computer permanently programmed to evaluate the state of charge. ### Claim 5 (depends on 4) A state of charge evaluator as claimed in claim 4 in which the computer comprises a microprocessor unit and an associated random-access-memory and read-only-memory, the read-only-memory containing a programme for evaluating the state of charge. ### Claim 6 (depends on 1) A state of charge evaluator as claimed in claim 1, in which the evaluator further comprises means responsive to the temperature of the electrolyte of the battery, the voltage value being compensated in accordance with this temperature. ### Claim 7 (depends on 1) A state of charge evaluator as claimed in claim 1, in which the battery is divided into a plurality of sub-packs, said computing means determining the state of charge from the voltage of the sub-pack having the lowest voltage. ### Claim 8 (depends on 7) A state of charge evaluator as claimed in claim 7, in which each sub-pack comprises a plurality of cells connected in series. ### Claim 9 (depends on 1) A state of charge evaluator as claimed in claim 1 in which the computing means computes the polarization voltage in accordance with the following equations: VP=A.multidot.(I).sup.B and T=C-D.multidot.1n(I) where VP is the polarization voltage as time tends to infinity, I is peak current, T is a time constant, and A, B, C and D are constants.