Method and apparatus for determining the state of charge of a lithium-ion battery
AssigneeHoneywell International Inc.
InventorsJames V. Guiheen, Harmohan Singh, Thirumalai G. Palanisamy
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Abstract
Computer-assisted methods for determining the state of charge of a specific lithium ion battery, without the need for charging and discharging the battery, by utilizing look-up tables or algorithms which store the relationships of state of charge to open-circuit voltage or to ramp-peak current, or to both for that type of specific lithium-ion battery to determine the state of charge for that specific lithium-ion battery.
Claims6
A method for creating a look-up table of ramp-current versus state of charge for a lithium-ion battery, said method comprising the steps of:
- (a) bringing the battery to a first present state of charge;
- (b) applying a monotonically increasing current to said battery from a power supply, where there is a dependence of current increase with time;
- (c) recording said dependence of current increase with time;
- (d) increasing said monotonically increasing current to said battery until the current reaches a value defined as the ramp-peak current at the first present state of charge for said lithium-ion battery where either
- (i) a measured voltage for said battery reaches a predetermined maximum, or
- (ii) said monotonically increasing current equals a maximum current rating of the power supply;
- (e) recording said ramp-peak current at the present state of charge;
- (f) repeating said steps (a), (b), (c), (d), and (e) for additional present states of charge, said recording step (e) recording said ramp-peak currents for the additional states of charge for said battery;
- and
- (g) creating the look-up table of ramp-peak current versus state of charge for the lithium-ion battery using the first and additional present states of charge for said battery.
The method in accordance with claim 1 wherein all the steps of claim 10 are repeated at a set of predetermined temperatures.
Dependencies are inferred from the claim text.