Method for determining state of charge of lead-acid batteries of various specific gravities
First Claim
Patent Images
1. A method of determining a state of charge (SOC) of a lead-acid battery having an unknown specific gravity, the method comprising the steps of:
- applying a current ramp to the battery while measuring battery voltage at terminals of the battery;
measuring presence of gas points during application of the current ramp;
determining a maximum voltage per cell (Vpc) for the battery;
estimating the SOC of the battery by applying a default low specific gravity of 1.28 having a known correlation curve;
when gas points are present, comparing the Vpc to an upper limit of a maximum measured battery voltage, measured during the step of applying the current ramp to the battery, divided by a number of cells in the battery (SGLIM);
when gas points are absent, comparing the estimated SOC to an SOC threshold value representing a maximum state of charge for which gas points should not be detectable;
determining a specific gravity of a lead-acid battery from one of the two comparing steps;
determining a rested state open circuit voltage of the lead-acid battery at a rested state; and
determining the SOC of the lead-acid battery at a rested state from the rested state open circuit voltage using a correlation function, wherein the correlation function depends on the specific gravity of the lead-acid battery.
1 Assignment
0 Petitions
Accused Products
Abstract
In accordance with various embodiments, there is a method for determining the state of charge of a battery. Various embodiments include the steps of determining the specific gravity of the battery and measuring an open circuit voltage of the battery at rest. The open circuit voltage at rest can be used to determine the battery state of charge from a correlation function dependent on the battery specific gravity.
-
Citations
12 Claims
-
1. A method of determining a state of charge (SOC) of a lead-acid battery having an unknown specific gravity, the method comprising the steps of:
-
applying a current ramp to the battery while measuring battery voltage at terminals of the battery; measuring presence of gas points during application of the current ramp; determining a maximum voltage per cell (Vpc) for the battery; estimating the SOC of the battery by applying a default low specific gravity of 1.28 having a known correlation curve; when gas points are present, comparing the Vpc to an upper limit of a maximum measured battery voltage, measured during the step of applying the current ramp to the battery, divided by a number of cells in the battery (SGLIM); when gas points are absent, comparing the estimated SOC to an SOC threshold value representing a maximum state of charge for which gas points should not be detectable; determining a specific gravity of a lead-acid battery from one of the two comparing steps; determining a rested state open circuit voltage of the lead-acid battery at a rested state; and determining the SOC of the lead-acid battery at a rested state from the rested state open circuit voltage using a correlation function, wherein the correlation function depends on the specific gravity of the lead-acid battery. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
-
Specification