POWERBOATER’S GUIDE TO ELECTRICAL SYSTEMS ber, this is a very low-amperage charging system—4, maybe as many as 9 amps are all you can expect. Operate the engine at a fairly high rpm; if the needle on the meter moves at all, your system is OK. If there is no movement, visually check all the electrical connections and terminals for corrosion and tightness. Clean and tighten them as needed. If your system is equipped with a fuse, you should check it visually or test for continuity through the filament with your ohmmeter. Check your engine’s owner’s manual for the location of the fuse if you have one. If everything seems OK then the problem is probably in the rectifier. Testing rectifiers is tricky without the wiring diagram for your engine. They don’t all look alike, and the wiring varies from one manufacturer to the next. The best approach for rectifier testing is to refer to your engine’s service manual. All you’ll need for equipment is your multimeter set to the diode-test scale. If you test the rectifier and determine that it’s OK, you must next test the stator. These are all different, so work from your engine’s manual, and if you’re uncertain of the procedure, consult your local dealer.
Regulated Outboard Systems Larger outboard engines (and, on the newest units, even the smaller ones) have voltage regulators installed into the circuitry. Sometimes these are combination regulator-rectifiers like you might find on an inboard system. If a component is going to fail in the system, it will most likely be this regulatorrectifier. The three-step voltage test described on pages 92–93 will work on these systems just like on inboard systems. It’s best to use your engine manual for the tests necessary to isolate charging system problems in the regulator.
Shore-Power Battery Charging Systems and Installations Permanently installed battery chargers connected to your boat’s shore-power system fall into one of two general categories. The most common is the ferroresonant constant-output charger. The other is known generically as a smart charger or three-step charger. 96
Many of the smart chargers available today also have a fourth stage known as an equalization stage and are thus four-step chargers. (More on that later.) A third popular type of battery charger is really a combined device known as an inverter-charger that not only converts 12-volt direct current into 120-volt alternating current, but also incorporates a quality multistage battery charger into one handy and compact unit. As you’ll see in the following descriptions, the differences between the basic types of battery chargers are significant.
Ferro-Resonant Battery Chargers Ferro-resonant battery chargers are deceptively simple devices, nothing more than a simple transformer (a ferro-resonant transformer) that converts 120-volt alternating current into 12-volt alternating current and a rectifier that converts the alternating current into direct current. The basic units, the simple household battery chargers sold at the auto parts store, work just fine for getting the car started on a cold morning or for a quick charge on a dead battery, but they have no place on your boat. Ferro-resonant chargers designed for use on boats are a little more complex than the basic units. They incorporate some elaborate circuitry that will gradually taper the charging current to roughly match the demands of your battery. The better ferro-resonant chargers work fine on wet-cell batteries, but even the best don’t do a very good job with the new gel-cell and AGM batteries. In fact, many of the problems associated with premature battery failure, such as a rottenegg odor and boiling of battery electrolyte (the result of constant overcharging), are often caused by the use of the ferro-resonant chargers. Unfortunately, some of the largest producers of powerboats, such as Bayliner and Sea Ray, still install ferro-resonant chargers in their boats because they are considerably less expensive than newer smart chargers. To determine which type of battery charger you have, you’ll need to find the charger itself. It will be mounted somewhere near the batteries. If you don’t see things like a battery-type selector switch or a temperature-compensation calibration switch somewhere on the charger, you probably have the ferro-
