By Purkeys | Aug 8, 2014

How to Measure AC Power Consumption



Long-haul truck drivers use inverters to convert DC power to AC power. This allows them to use 110 V appliances like microwaves and computer chargers. When the truck’s engine is off, all of the electricity to run these hotel loads comes from the truck’s batteries. Overconsumption of AC power leads to dead batteries and extra jumpstart costs.

It is important to realize that a seemingly small AC load is actually much larger once converted back to DC power. To estimate the extra draw off the batteries start by converting AC power back to DC power. To do so, divide the wattage of an inverter by 10 volts. Use 10 volts instead of 12 volts to account for loss of efficiency when converting from DC to AC. For example, a 1,000 watt microwave at 12 volts would be pulling 83 amps out of the battery but when you estimate the loss of efficiency during the DC to AC conversion formula might look like this:

  • 1000 watt = 10 volts x 100 amps

100 amps is a much larger draw and can drain the batteries much faster than expected.

Fleets and drivers can work together to avoid the overconsumption of AC power. Purkeys offers a smart inverter that will shut off when the batteries drop below certain voltage. This voltage set point is higher than the typical inverter’s set point to ensure there is still enough energy in the batteries to start the truck. Drivers can conserve their AC power use by:

  • Turning the truck on when using devices that take a heavy load, such as microwaves
  • Monitoring how many small loads are going at once

A smart inverter combined with AC power awareness can reduce a fleet’s jumpstarts and extend the life of truck batteries. It also will reduce downtime, increase productivity and generate more revenue.


Are you dealing with battery issues? Have you looked into converters? We welcome your comments and questions below.

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