Method and apparatus for predicting temperature based state-of-charge

A back-up power source for an electronic module connected to a primary power source, comprising:

• a power source having an initial ampere-hour rating and a nominal self-discharge rate;
• a temperature measuring device configured to measure the temperature of the power source;
• and
• a processor associated with the electronic module and coupled to the—temperature measuring device;
• wherein the processor is configured to receive the temperature measurements of the power source from the temperature measuring device, and to calculate therefrom a temperature-adjusted self-discharge quantity for the power source, and wherein the processor is further configured to calculate an estimated remaining state-of-charge of the power source, based on the reduction of the initial ampere-hour rating due to the temperature-adjusted self-discharge quantity, and on the further reduction of the initial ampere-hour rating due to a cumulative parasitic leakage current draw, a cumulative voltage sampling check current draw, and a cumulative low power mode transient current draw.

A method for estimating the remaining state-of-charge of a power source, the method comprising the following algorithm:

• C(N)=C0*{1−SUM[R*E1+R*E2]}−IL*TL−IM*TM−IC*TC
• where C(N) is the remaining state-of-charge;
• where C0 is an initial state-of-charge of the non-rechargeable power source;
• where R is a nominal self-discharge rate for the non-rechargeable power source;
• where E1 is a temperature-adjusted discharge factor;
• where E2 is a temperature-averaged discharge factor;
• where IL*TL is a cumulative parasitic leakage current draw;
• where IM*TM is a cumulative monitor current draw;
• and
• where IC*TC is a voltage check current draw.