# US 2021/0344204 A1 · Power storage device and charging method

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- Number: US 2021/0344204 A1
- Document ID: US20210344204A1
- Status: Published application
- Kind: A1
- Application number: 17/268,912
- Filed: 2019-06-14
- Published: 2021-11-04
- Earliest claimed: 2018-09-07
- Assignees: Fdk Corporation
- Applicants: Fdk Corporation
- Inventors: Shun Mochizuki
- Web page: https://patentgrep.com/patent/US20210344204A1

## CPC

- H02J 7/54: Passive balancing, e.g. using resistors or parallel MOSFETs
- H01M 10/441: {for several batteries or cells simultaneously or sequentially}
- H01M 10/48: Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte (constructional details of current conducting connections for detecting conditions inside cells or batteries, e.g. details of voltage sensing terminals, H01M50/569)
- H01M 50/51: Connection only in series
- H02J 7/02: for charging batteries from AC mains by converters
- H02J 7/56: Active balancing, e.g. using capacitor-based, inductor-based or DC-DC converters
- H02J 7/96: in response to battery voltage
- H02J 7/80: including monitoring or indicating arrangements
- H02J 9/062: {for AC powered loads}
- Y02E 60/10: Energy storage using batteries
- H02J: ELECTRIC POWER NETWORKS; CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- 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

## Abstract

A power storage device 1 includes first power storage unit BBU1 to seventh power storage unit BBU7 connected in series and a control unit 10 for monitoring each unit voltage and controlling each of the power storage units, each power storage unit BBU 1-7 includes a power storage portion BAT and a charge switch SWC connected in series between charge/discharge terminals T and a bypass switch SWB providing a bypass between the charge/discharge terminals T, and for the respective power storage units connected in series, the control unit 10 equalizes the unit voltages by individually setting a charging mode in which the bypass switch SWB is controlled to be set to OFF while the charge switch SWC is controlled to be set to ON to charge the power storage portion BAT with a constant current, and a bypass mode in which the bypass switch SWB is controlled to be set to ON while the charge switch SWC is controlled to be set to OFF to stop charging of the power storage portion BAT.

## Claims

### Claim 1

A power storage device comprising:
a plurality of power storage units connected in series; and
a control unit for monitoring a unit voltage of each of the plurality of power storage units and controlling each of the plurality of power storage units, wherein each of the power storage units includes a power storage portion and a charge switch which are connected to each other in series between charge/discharge terminals, and a bypass switch providing a bypass between the charge/discharge terminals,
wherein, for the plurality of power storage units to be charged in series, the control unit individually sets a charging mode in which the power storage portion is charged with a constant current by controlling the bypass switch to be set to OFF while controlling the charge switch to be set to ON, and a bypass mode in which the charging of the power storage portion is stopped by controlling the bypass switch to be set to ON while controlling the charge switch to be set to OFF, thereby equalizing the unit voltages.

### Claim 2 (depends on 1)

The power storage device according to claim 1, wherein the control unit increases a number of the power storage units to be set to the bypass mode as the charging of the plurality of power storage units progresses.

### Claim 3 (depends on 1)

The power storage device according to claim 1, wherein the control unit controls a number NC of the power storage units to be set to the charging mode so that the number NC is equal to a minimum natural number satisfying NC≥VCUTOFF×NTOTAL/VTOTAL when a discharge termination voltage of the power storage unit is represented by VCUTOFF, a series connection number of the power storage units is represented by NTOTAL, and a total voltage of the plurality of power storage units is represented by VTOTAL.

### Claim 4 (depends on 1)

The power storage device according to claim 1, wherein each power storage unit includes a discharge switch connected in parallel to the charge switch, and when power outage occurs during charging of the plurality of power storage units, for all the power storage units, the control unit controls the charge switches and the bypass switches to be set to OFF and controls the discharge switches to be set to ON.

### Claim 5

A charging method for charging a plurality of power storage units connected in series, comprising:
a voltage monitoring step of monitoring a unit voltage of each of the plurality of power storage units; and
a series charging step of performing series charging on each of the plurality of power storage units while equalizing the unit voltages by individually setting either a charging mode in which an internal power storage portion is charged with a constant current or a bypass mode in which the internal power storage portion is bypassed to stop charging.

### Claim 6 (depends on 5)

The charging method according to claim 5, wherein, in the series charging step, a number of the power storage units to be set to the bypass mode is increased as the charging of the plurality of power storage units progresses.

### Claim 7 (depends on 5)

The charging method according to claim 5, wherein, in the series charging step, a number NC of the power storage units to be set to the charging mode is controlled to be equal to a minimum natural number satisfying NC≥VCUTOFF×NTOTAL/VTOTAL when a discharge termination voltage of the power storage unit is represented by VCUTOFF, a series connection number of the power storage units is represented by NTOTAL, and a total voltage of the plurality of power storage units is represented by VTOTAL.

### Claim 8 (depends on 5)

The charging method according to claim 5, wherein, in the series charging step, when power outage occurs during charging of the plurality of power storage units, all the power storage units are set to a discharging mode in which charging of internal power storage portions thereof is stopped to discharge the power storage portions.

### Claim 9 (depends on 2)

The power storage device according to claim 2, wherein the control unit controls a number NC of the power storage units to be set to the charging mode so that the number NC is equal to a minimum natural number satisfying NC≥VCUTOFF×NTOTAL/VTOTAL when a discharge termination voltage of the power storage unit is represented by VCUTOFF, a series connection number of the power storage units is represented by NTOTAL, and a total voltage of the plurality of power storage units is represented by VTOTAL.

### Claim 10 (depends on 2)

The power storage device according to claim 2, wherein each power storage unit includes a discharge switch connected in parallel to the charge switch, and when power outage occurs during charging of the plurality of power storage units, for all the power storage units, the control unit controls the charge switches and the bypass switches to be set to OFF and controls the discharge switches to be set to ON.

### Claim 11 (depends on 6)

The charging method according to claim 6, wherein, in the series charging step, a number NC of the power storage units to be set to the charging mode is controlled to be equal to a minimum natural number satisfying NC≥VCUTOFF×NTOTAL/VTOTAL when a discharge termination voltage of the power storage unit is represented by VCUTOFF, a series connection number of the power storage units is represented by NTOTAL, and a total voltage of the plurality of power storage units is represented by VTOTAL.

### Claim 12 (depends on 6)

The charging method according to claim 6, wherein, in the series charging step, when power outage occurs during charging of the plurality of power storage units, all the power storage units are set to a discharging mode in which charging of internal power storage portions thereof is stopped to discharge the power storage portions.