When a customer meets the limitations of electrodynamics

More than a decade ago, a customer brought his late-1990s Suzuki Sidekick into our shop and asked us to install a 2,000-watt power inverter that he had purchased. His goal was to have 120-volt household power available while using the vehicle.

The job seemed straightforward. We connected the inverter to the vehicle's electrical system and mounted it in the rear cargo area, per the customer's request. After installation, we tested the unit, verified that it was producing 120 volts, and returned the vehicle to the customer.

A few weeks later, the customer came back frustrated, insisting that the inverter was not working. We inspected the system and found nothing wrong. To verify its operation, we plugged in a shop vacuum and confirmed the inverter powered it without issue.

Curious about the application, we asked the customer what he was using the inverter for. He explained that he was an avid hunter and owned specialized hunting overalls that required heat activation to help mask human scent while in the woods. To warm the garment before hunting, he was plugging a portable clothes dryer into the inverter.

Electrical power can be calculated using the formula:

Watts = Volts × Amps

Under ideal conditions and at higher engine speeds, the alternator could produce roughly:

14 volts × 55 amps = 770 watts

Even at maximum output, the alternator was capable of supplying only about half the power required by the dryer. There was simply no way that the small factory charging system could continuously support a 1,400-watt load.

The customer then asked whether we could install a larger alternator. In theory, a 100-amp or larger alternator would be required to approach the demand of the dryer. However, no such alternator was readily available for that Suzuki application. Even if one could be adapted, the engine would likely need to operate at elevated RPM for an extended period to maintain the necessary electrical output. After evaluating the situation, we declined the modification. The requested setup exceeded the practical capabilities of the vehicle's charging system and would have introduced reliability and durability concerns.

Lesson Learned

This experience highlights an important principle in automotive electrical systems: installing a high-capacity inverter does not create power. The inverter can only convert the electrical energy that the vehicle's charging system can supply. Without sufficient alternator output, even the largest inverter is limited by the power available from the vehicle itself. In short, the inverter wasn't the problem. The customer was asking a compact SUV's charging system to power an appliance that demanded nearly twice the electrical energy the vehicle could produce.