# US 11,309,557 B2 · Method to control maximum current for a fuel cell

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 11,309,557 B2
- Document ID: US11309557B2
- Status: Granted
- Kind: B2
- Application number: 16/730,140
- Filed: 2019-12-30
- Published: 2020-04-30
- Granted: 2022-04-19
- Earliest claimed: 2015-09-29
- Assignees: Intelligent Energy Limited
- Applicants: Intelligent Energy Limited
- Inventors: Jeremy Bowman
- Web page: https://patentgrep.com/patent/US11309557B2

## CPC

- H01M 8/04302: applied during start-up
- H01M 8/04303: applied during shut-down
- H01M 8/0432: Temperature; Ambient temperature
- H01M 8/04492: Humidity; Ambient humidity; Water content
- H01M 8/04559: {of fuel cell stacks}
- H01M 8/04589: {of fuel cell stacks}
- H01M 8/0488: {of fuel cell stacks}
- H01M 8/0491: {of fuel cell stacks}
- Y02E 60/10: Energy storage using batteries
- Y02E 60/50: Fuel cells
- Y02T 90/40: Application of hydrogen technology to transportation, e.g. using fuel cells
- H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

The disclosure relates to a fuel cell stack and corresponding method of operating the fuel cell stack. The method comprises: determining a maximum allowable current that may be drawn from the fuel cell stack; repeatedly determining a magnitude of change to the prevailing maximum allowable current based on a prevailing allowable current ramp rate and an actual measured current of the fuel cell stack; updating the maximum allowable current according to the periodically determined magnitude of change; and controlling operating parameters of the fuel cell stack according to the prevailing maximum allowable current.

## Claims

### Claim 1

A method of operating a fuel cell system comprising:
repeatedly determining a maximum allowable current that may be drawn from the fuel cell system based on at least one of a prevailing allowable current ramp rate, an actual measured current of the fuel cell system, and a parasitic current load of the fuel cell system; and
controlling a plurality of operating parameters of the fuel cell system according to a most recent determination of the maximum allowable current as a function of one or more of:
(i) a total system running time;
(ii) a count of the total number of full stop-start cycles to which the fuel cell system has been subjected;
(iii) an ambient humidity falling below a predetermined low humidity threshold;
(iv) an ambient temperature falling below a predetermined low temperature threshold;
(v) an ambient temperature rising above a predetermined high temperature threshold;
(vi) a system voltage;
(vii) the proximity of one or more cell voltages to a minimum cell voltage threshold and/or the proximity of a system temperature to a maximum temperature limit and,
(viii) the maximum allowable current does not fall below a predetermined minimum current limit.

### Claim 2 (depends on 1)

The method of claim 1 in which the step of controlling operating parameters of the fuel cell system comprises controlling an electrical load on the fuel cell system.

### Claim 3 (depends on 1)

The method of claim 1 in which the most recent determination of the maximum allowable current comprises an increment or a decrement with respect to a less recent determination of the maximum allowable current.

### Claim 4 (depends on 1)

The method of claim 1 in which the most recent determination of the maximum allowable current is determined according to the smaller of a magnitude of change corresponding to the prevailing allowable current ramp rate and a magnitude of change indicated by a current load requirement.

### Claim 5 (depends on 1)

The method of claim 1 in which the most recent determination of the maximum allowable current is determined as a function of a period of time corresponding to a drying time of one or more fuel cells of the fuel cell system.

### Claim 6 (depends on 1)

The method of claim 1 further including the step of periodically determining an allowable current ramp rate as a function of an actual measured current and a presently prevailing current ramp rate and at least one of: a rated maximum current for the system; a maximum ramp rate based on the capability of the fuel and/or oxidant delivery system; a period of time corresponding to a drying time of one or more fuel cells of the fuel cell system; and a period of time corresponding to a wetting time of the one or more fuel cells of the fuel cell system.

### Claim 7 (depends on 6)

The method of claim 6 in which the rated maximum current comprises a predetermined maximum current for the physical configuration of the fuel cell system.

### Claim 8 (depends on 1)

The method of claim 1 further including the step of inhibiting an increase in the maximum allowable current in the event of one or more of:
(i) a temperature of one or more cells exceeding a predetermined temperature threshold;
(ii) one or more cell voltages falling below a predetermined cell voltage threshold;
(iii) plural cell voltages exceeding a predetermined range.

### Claim 9 (depends on 1)

The method of claim 1 further including the step of overriding the maximum allowable current in the event of one or more of:
(i) the system entering a shutdown procedure;
(ii) one or more fuel cells of the system being isolated from a load.

### Claim 10 (depends on 1)

A fuel cell system comprising:
one or more fuel cells disposed in series or in parallel; and
a controller conformed to perform the method of claim 1; and,
in which the one or more fuel cells are air cooled fuel cells.

### Claim 11 (depends on 10)

A vehicle comprising the fuel cell system of claim 10 for powering said vehicle.