Claims:1. A controller (110) to determine capacity imbalance of cells (114) in a battery
pack (102), said battery pack (102) comprising plurality of cells (114),
characterized by,
measure and log a parameter of each cell (114) 5 in a memory unit
(108) with increase in monitored capacity of said battery pack (102);
select one cell from said plurality of cells (114) as a reference cell
(104) , and
determine a capacity offset for each of said remaining cells (106) in
10 relation to said reference cell (104), said capacity offset is said to be
determined when a correlation between profiles of said parameter of
said reference cell (104) and that of each of said remaining cells
(106), is maximum.
2. The controller (110) as claimed in claim 1, wherein said parameter is
selected from a group comprising a voltage and a voltage gradient, wherein
said voltage gradient is defined as rate of change of voltage with rate of
change of capacity of said battery pack (102).
3. The controller (110) as claimed in claim 1, wherein said determination of
capacity imbalance is performed while said battery pack (102) is being
charged.
4. The controller (110) as claimed in claim 1, wherein said capacity imbalance
25 is determinable during capacity increase of said battery pack (102), i.e.
before reaching full capacity of said battery pack (102).
5. The controller (110) as claimed in claim 1, wherein said battery pack (102)
is Lithium-ion battery pack (102), wherein said Lithium-ion battery is
30 Lithium iron phosphate battery (LiFePO4 battery) or LFP battery.
6. A method for determining capacity imbalance of cells (114) in a battery
pack (102), said method comprising the steps of:
measuring and logging a parameter of each cell (114) in a memory
unit (108) of a controller (110), with increase in capacity of said
5 battery pack (102);
selecting one cell from said plurality of cells (114) as a reference
cell, and
determining a capacity offset for each of said remaining cells (106)
in relation to said reference cell (104), said capacity offset is said to
10 be determined when a correlation between profiles of said parameter
of said reference cell (104) and said parameter of each of said
remaining cells (106), is maximum.
7. The method as claimed in claim 6, wherein said parameter is selected from
15 a group comprising a voltage and a voltage gradient, wherein said voltage
gradient is defined as rate of change of voltage with rate of change of
capacity of said battery pack (102).
8. The method as claimed in claim 6, wherein said determination of capacity
20 imbalance is performed while said battery pack (102) is being charged.
9. The method as claimed in claim 6, wherein said capacity imbalance is
determinable during capacity increase of said battery pack (102), i.e. before
reaching full capacity of said battery pack (102).
10. The method as claimed in claim 6, wherein said battery pack (102) is
Lithium-ion battery pack (102), wherein said Lithium-ion battery is Lithium
iron phosphate battery (LiFePO4 battery) or LFP battery. , Description:The controller 110 determines the capacity/SOC imbalance of cells in the battery
pack 102. The battery pack 102 comprising plurality of cells 114. The controller
110, characterized by, configured to measure and log a parameter of each cell 114
in a memory unit 108 with increase in monitored capacity of the battery pack 102.
The controller 110 further selects one cell as a reference cell 104 from the plurality
of cells 114. The controller 110, further determines a capacity offset of each of the
remaining cells 106 in relation to the reference cell 104, using the logged data. The
capacity offset is determined when a correlation between profiles/pattern of the
parameter of the reference cell 104 and that of each of remaining cells 106, is
maximum. An innovative application of electrochemical behavior coupled with
statistics to simplify the need for cell balancing is provided.