Battery management apparatus and method for protecting a lithium iron phosphate cell from over-voltage using the same

Patent metadata

Field	Value
Publication number	US-10873201-B2
Application number	US-201716314775-A
Country	US
Kind code	B2
Filing date	Dec 4, 2017
Priority date	Jan 2, 2017
Publication date	Dec 22, 2020
Grant date	Dec 22, 2020

Abstract

A battery management, including a voltage measuring unit electrically connected to multiple lithium iron phosphate (LFP) cells in an LFP battery, the LFP cells being connected in series, to individually measure voltage of each LFP cell and output a voltage value indicative of the measured voltage, and a control unit configured to output a first signal requesting the start of a charging process of the LFP, and when at least one of the voltage values of the multiple LFP cells outputted from the voltage measuring unit reaches a threshold voltage value while the charging process is performed by the first signal, output a second signal requesting the stop of the charging process and output a third signal requesting the start of a discharging process.

First claim

What is claimed is:

1. A battery management apparatus comprising:
a voltage measuring unit electrically connected to multiple lithium iron phosphate (LFP) cells in a LFP battery, the LFP cells being connected in series, to individually measure a voltage of each LFP cell and output a voltage value indicative of the measured voltage; and
a control unit configured to:
output a first signal to a charger requesting the start of a charging process of the LFP battery by the charger, and
when at least one of the voltage values of the multiple LFP cells outputted from the voltage measuring unit reaches a threshold voltage value while the charging process is performed by the charger due to the first signal, output a second signal to the charger requesting the stop of the charging process and output a third signal to the charger requesting the start of a discharging process,
wherein the charging process is designed to increase a voltage supplied to the LFP battery stepwise from a preset initial target charge voltage value to a final target charge voltage value, and
the discharging process is designed to reduce the voltage supplied to the LFP battery stepwise from a preset initial target discharge voltage value to a final target discharge voltage value.

2. The battery management apparatus according to claim 1 , wherein the initial target charge voltage of the charging process is larger than the initial target discharge voltage of the discharging process.

3. The battery management apparatus according to claim 1 , wherein the control unit is configured to determine the threshold voltage value by subtracting a voltage margin value corresponding to a delay time from a preset upper limit of charge voltage value of the respective LFP cell.

4. The battery management apparatus according to claim 3 , wherein the control unit is configured to determine the delay time based on at least one of a first elapsed time and a second elapsed time,
wherein the first elapsed time is a period from an output time of the first signal to a start time of the charging process by the first signal, and
wherein the second elapsed time is a period from an output time of the third signal to a start time of the discharging process by the third signal.

5. The battery management apparatus according to claim 1 , further comprising:
a current measuring unit configured to measure a current of the LFP battery, and output a current value indicative of the measured current.

6. The battery management apparatus according to claim 5 , wherein the control unit is configured to:
calculate partial discharge capacity of the LFP battery by integrating the current value outputted from the current measuring unit over time from the time the discharging process starts, and
output a fourth signal requesting the stop of the discharging process when the partial discharge capacity reaches a discharge reference ratio to remaining capacity of the LFP battery at the time the charging process is stopped.

7. The battery management apparatus according to claim 6 , wherein the discharge reference ratio is 3%.

8. The battery management apparatus according to claim 5 , wherein the control unit is configured to output a fifth signal requesting the rise of voltage supplied to the LFP battery each time the current of the LFP battery reaches a first threshold current value during the charging process.

9. The battery management apparatus according to claim 5 , wherein the control unit is configured to output a sixth signal requesting the drop of voltage supplied to the LFP battery each time the current of the LFP battery reaches a second threshold current value during the discharging process.

10. The battery management apparatus according to claim 1 , wherein the discharging process starts after the voltage supplied to the LFP battery reduces in accordance with a predefined slew rate from a voltage value at the time the charging process is stopped by the second signal to the initial target discharge voltage value.

11. A battery pack comprising:
the battery management apparatus according to claim 1 ; and
a load device, the load device including the charger.

12. A method for protecting a lithium iron phosphate (LFP) cell from overvoltage in which an LFP cell included in an LFP battery is protected from overvoltage using a battery management apparatus, the method comprising:
outputting, by the battery management apparatus, a first signal to a charger requesting the start of a charging process of the LFP battery;
outputting, by the battery management apparatus, a second signal to the charger requesting the stop of the charging process when at least one of voltage values of multiple LFP cells reaches a threshold voltage value while the charging process is performed by the charger due to the first signal; and
outputting, by the battery management apparatus, a third signal to the charger requesting the start of a discharging process after the charging process is stopped by the second signal,
wherein the charging process is designed to increase the voltage supplied to the LFP battery stepwise from a preset initial target charge voltage value to a final target charge voltage value, and
wherein the discharging process is designed to reduce the voltage supplied to the LFP battery stepwise from a preset initial target discharge voltage value to a final target discharge voltage value.

Assignees

• Lg Chemical Ltd

Inventors

• Cha Sun-Young
• Joe Won-Tae

Classifications

• H02J7/975

  in response to temperature · CPC title

• H02J7/963

  in response to battery voltage gradient · CPC title

• H02J7/96

  in response to battery voltage · CPC title

• H02J7/94

  in response to battery current · CPC title

• H01M10/486

  for measuring temperature · CPC title