What is special about a high-amp alternator? What is "duty cycle"?

Duty cycle is a specification which defines the number of minutes, within a 10 minute period, during which a given alternator can safely produce a particular amount of charging current -- delivered into a restive load.

For example, a 150 amp car alternator will typically have a 30% duty cycle. The alternator can charge continuously at 50 amps -- but if operating at full power, it should be "rested" for at least 7 minutes after 3 minutes of continuous high amp charging.

On the other hand, a 150 amp high amp/ambulance duty alternator will typically have a 100% duty cycle. This alternator can generate continuously at 150 amps -- into a restive load

Failure to carefully observe duty cycle limitations can easily over stress a alternator -- contributing to premature failure.

Alternators do not have internal protection systems that prevent this sort of over stress -- leaving the task to the owner or operator.

Look carefully at your alternators specifications -- and the warranty that comes with it. Most alternator manufacturers will identify a particular alternator by its maximum possible power generation capacity, even though that alternator may only be able to produce that level of power for a very short period of time.

ALL ZENA^® alternators are rated at their 100% duty cycle power capability.

Don't make the mistake of comparing a commercial duty, 100% duty cycle alternator (like a ZENA unit) with alternator which promise high output currents, but which are actually severely limited by low duty cycle performance.

Need help comparing alternator? Call us.