Electrical Load Management: Notes

Power management function is designed to monitor vehicle electrical load and determine when battery is potentially in a high discharge condition. This is accomplished by using a high accuracy battery voltage reading as an indicator of battery discharge rate. DIM calculates battery temperature, voltage and charging rate at all times while engine is running. DIM calculates battery temperature by factoring in current intake manifold air temperature compared to last temperature recorded when ignition switch was turned to OFF position, current battery voltage compared to last battery voltage recorded when ignition switch was turned to OFF position and length of time since last battery temperature calculation. Six levels of load management will execute in load management control algorithm when there is a high discharge condition:

1. Idle speed increase message to Powertrain Control Module (PCM) to raise alternator output. See Idle Speed Increase .
2. A greater vehicle idle speed increase message to PCM.
3. Reduction of electrical loads. See Loads Subject To Reduction .
4. Another vehicle idle speed increase to PCM.
5. Additional reduction of electrical loads.
6. Additional reduction of electrical loads.

Each load management function, either idle boost or load-shed, is discrete. No two functions are implemented at same time. During each load management function, DIM checks battery temperature, battery voltage and amp-hour calculations and determines if DIM should implement a different power management function.