Vehicle battery management unit having cell balancer based on capacity differences of battery cells

Patent metadata

Field	Value
Publication number	US-9278622-B2
Application number	US-201313937316-A
Country	US
Kind code	B2
Filing date	Jul 9, 2013
Priority date	Jul 10, 2012
Publication date	Mar 8, 2016
Grant date	Mar 8, 2016

Abstract

The battery management unit for a vehicle includes a charger mounted on the vehicle, configured to connect to an external power source and charge an assembled battery including a plurality of cells with electric power from the external power source; a memory that records which cell is a lowest cell having the lowest voltage when the battery is fully charged; and a cell-balancer that carries out cell-balancing on the voltage of the battery by discharging, when the charger is not charging the battery, the cells having a voltage higher than a current voltage of the lowest cell to the current value of the lowest cell.
Thereby, it is possible to suppress an increase in dispersion of voltages and reduction in battery capacity.

First claim

What is claimed is:

1. A battery management unit for a vehicle comprising:
a charger mounted on the vehicle, configured to connect to a commercial external power source and charge an assembled battery including a plurality of cells with electric power from the external power source;
a memory that records which cell is a lowest cell having the lowest voltage when the assembled battery is fully charged by the external power source among the plurality of cells; and
a cell-balancer that carries out cell-balancing on the voltage of the assembled battery by discharging, when the charger is not charging the assembled battery, one or more cells each currently having a voltage higher than a current voltage of the lowest cell to the current voltage of the lowest cell.

2. The battery management unit according to claim 1 , further comprising:
a calculator that calculates a cell capacity difference based on the difference between a lowest voltage and a highest voltage among voltages of the plurality of cells when the assembled battery is fully charged; and
a setter that sets an upper limit of cumulative time of carrying out the cell-balancing based on a consumption electric current of the cell-balancing and the cell capacity difference calculated by the calculator, wherein
the cell-balancer prohibits the cell-balancing from being carried out for cumulative time longer than the upper limit set by the setter.

3. The battery management unit according to claim 2 , wherein the setter resets the upper limit whenever the assembled battery is fully charged.

4. The battery management unit according to claim 1 , wherein one of the conditions to carry out the cell-balancing is that the cell-balancer sets the absolute value of charging or discharging electric current being less than a criterial value.

5. The battery management unit according to claim 2 , wherein one of the conditions to carry out the cell-balancing is that the cell-balancer sets the absolute value of charging or discharging electric current being less than a criterial value.

6. The battery management unit according to claim 3 , wherein one of the conditions to carry out the cell-balancing is that the cell-balancer sets the absolute value of charging or discharging electric current being less than a criterial value.

Assignees

• Mitsubishi Motors Corp

Inventors

• Tagaya Naoto
• Muramatsu Katsuyoshi

Classifications

• H02J7/54

  Passive balancing, e.g. using resistors or parallel MOSFETs · CPC title

• H02J7/52

  for charge balancing, e.g. equalisation of charge between batteries · CPC title

• H01M10/446

  Initial charging measures · CPC title

• B60L11/1866

  Operations & Transport · mapped topic

• H02J7/0016

  Electricity · mapped topic