The alternator installed on the Yanmar 4JHE is from Hitachi. Already at idle, it charges the batteries with approx. 20 A and thus falls under the category of high performance. Unfortunately, the internal regulator doesn’t allow more than 25 A charging current. With the renewal of the electrical system, we replaced the previous alternator (55 A) by a stronger one (80 A). Only a few millimeters bigger in diameter the installation was an easy task. A high-performance controller from Sterling operates the alternator. Wiring was straightforward; the regulator replaces the isolating diodes. We were curious about the first test and it fulfilled all expectations. Instead of the usual 25 A, the ammeter showed almost 70 A. Compared to generators with 120 A and more amps this may not be much, but the installation of a high-performance alternator is not all it takes, as several boat builders and electricians explained credibly. These generators need efficient cooling. Nothing for a narrow engine compartment. We almost had burned the generator. Fortunately, the Sterling has temperature control and switched off the alternator. The solution is a strong fan whose airflow serves directly for cooling. The temperature while charging is about 70 degrees and thus below the 90 degrees C limit.
Besides the high charging current, the Sterling regulator has various charging characteristics and voltages that to be set depending on the type of battery. It charges the batteries in three stages – bulk, absorption, float. Not only the LEDs on the charger indicate the current state of charge, but it can also be checked via the battery monitor as well.