There was a time when choosing a high power alternator was a simple matter of determining how much output capacity you needed, but that is no longer the case. Today, you have to consider a number of factors that include fit, the idle output versus the rated and maximum outputs, and even the size of the drive belt. Of course, it’s also important to consider both manufacturing specifications and testing procedures, which is why it’s a good idea to verify that a high output alternator conforms to all of the pertinent standards from the IEC, ISO, and other relevant organizations.
1. Direct Fit High Output Alternators
The first thing to look for in a high output alternator is whether it is a direct fit unit. This essentially means that the high output alternator will replace your existing unit without extensive modifications, brackets, or spacers.
In order to verify that a high output alternator will work in your application, it’s important to know the dimensions and the mounting style of both the replacement unit and the original one. Comparing the dimensions will allow you to determine whether the unit will physically fit, and verifying that both units have the same mounting style (e.g., single foot, saddle) is also a good idea. Of course, it’s even better if the supplier can verify that a unit will fit in your particular application.
2. The Power Output Reality Check
The easiest way to determine how much power output you need is to add up the power requirements of your vehicle’s electrical system, figure in the amount of amperage required to charge the battery or batteries, and then add in a 20 to 50 percent buffer. However, choosing the right high power alternator is a little more complicated than that.
After you know how much power you need, it’s vital to understand the difference between idle output, rated output, and maximum output. The idle output of an alternator is the amount of amperage it can provide when the vehicle is idling, so that is typically the most important number to look at. If your electrical system requires a constant 300A, and you select an alternator with a rated or maximum output of 300A, you will run into problems whenever the engine is idling.
3. The Importance of Belt and Pulley Sizes
When looking at high power alternators, it’s also important to take belt load limitations into consideration. The fact is that drive belts have load limitations based on size, which means you may need a different belt and pulley setup than the one you’re currently working with. Thin V belts can’t handle the same loads that thicker ones can, and even thick V belts are significantly less capable than serpentine belts.
If your application uses a single V belt, you may need to install a new crank pulley in order to use a high output alternator. For instance, a single 3/8″ V belt typically can’t handle anything over 80A, but dual 1/2″ V belts can handle a 310A high output alternator.
Of course, it’s also important to take the size of both the alternator and crank pulleys into consideration. Since alternators are typically designed to spin at least two times the speed of the engine, it’s important to maintain that ratio between the crank pulley and any replacement high output alternator. If the pulley of a high output unit is too big in comparison to the crank pulley, the alternator won’t spin fast enough, and your electrical system may not receive enough power.
4. Conformity with International Standards
Although it’s important for every alternator to conform with standards that are set out by organizations like the IEC, ISO , and SAE, it’s doubly important in the case of high output units. This is due to the fact that high output alternators are capable of putting out a lot of current, which can result in a significant safety risk if the unit wasn’t constructed and tested according to the most stringent methods. With that in mind, a high output alternator should meet or exceed the standards set out in documents like IEC 60034, and it should pass the testing requirements set by documents like ISO 8864 and SAE J 56 with flying colors.
If you’re looking for a reliable alternator supplier, view our catalogue and request a quote!