May 20, 2024

Automotive load managers for emergency vehicles are designed to monitor and control the transfer of electrical energy in an automotive system. The most advanced load managers will incorporate load sequencing and load shedding functions. These two functions will help maintain the vehicles optimal electrical state, which is paramount for any emergency vehicle.

The load sequencing function is used to turn all selected loads ON or OFF from on central switch. Loads can be anything from, emergency lights, sirens, A/C, radios, etc. When electrical loads of the type encountered in an automotive application are switched ON or OFF they create large current and voltage fluctuations in the electrical system in which they are connected. The larger the current consumption of a load, the greater the impact the load has in the generation of electrical transients or line noise when the load is energized or deenergized (Turned ON or OFF).

These current fluctuations, in turn, contribute to the generation of voltage spikes of a magnitude that is high enough to damage sensitive electronic devices connected to the electrical system. This would be the last thing you want while riding in an emergency vehicle. The load sequencing function of a good load manager will allow you to turn all the selected loads ON or OFF from one location to minimize electrical disturbances and the effect this action may have upon the rest of the electrical system. The load shedding function is used to monitor the voltage level of the vehicles battery. If a decrease in the battery voltage is sensed, the load manager will start shedding loads. A good load manager will allow you to program what loads and in what sequence they will be shed. One the loads battery voltage returns to its normal value, the loads that were previously shed are switched on.

The examples in the previous paragraphs were for when a vehicle is in motion. If the vehicles alternator is not supplying enough power when the vehicle is idling, the load manager should have a high idle function which will send a signal the vehicles engine speed control to set the idle speed to a higher level. An action equivalent to pressing the accelerator while in park. The higher engine speed is maintained until the battery voltage returns to normal or until the engine is no long idling.