Patent ID: 7725275

Claim:
A process for evaluating parasitic load on an electrical storage battery of a vehicle having an engine and an on-board electrical storage battery, said vehicle operative in alternating engine-on and engine-off states, comprising: for each of a plurality of engine-off states to obtain a plurality of equations: determining a first estimate of the state of charge of the battery at a first time substantially just prior to the beginning of an engine-off state or during said engine-off state; determining a second estimate of the state of charge of the battery at a second time during said engine-off state subsequent to the first estimate of the state of charge determination; determining an elapsed time between said first time and said second time; and determining an estimate of the parasitic load of the battery based on the difference between the first and second estimates of state of charge of the battery and said elapsed time; each equation having the form: δ=( S off −S on )× C=P×T+ε in which S off is the respective estimate of the state of charge of the battery substantially contemporaneous with the beginning of an engine-off state, and S on is the respective estimate of the state of charge of the battery substantially just prior to the beginning of the engine-on state that immediately follows the engine-off state, C is the battery reserved capacity in ampere*hours, P is the estimated parasitic load, T is an elapsed time between S off and S on , δ is state of charge loss of the battery during the elapsed time T, and ε is a constant, so as to provide a set of linear equations of the form: [ δ 1 δ 2 ⋮ δ M ] = [ t 1 1 t 2 1 ⋮ ⋮ t M 1 ] · [ P ɛ ] in which M is the number of observations, t i (i=1 . . . M) is the instance of elapsed time and δ i (i =1 . . . M) is the instance of state of charge loss; and solving the set of linear equations to provide a statistical estimation of the parasitic load across the plurality of engine-off states.