In the simplest of terms, an AC generator supplies power directly to a 120-volt circuit to run AC accessories throughout a boat, as well as charge the boat’s batteries (through an AC-to-DC charger). A DC generator, on the other hand, directly charges the boat’s batteries, which can, in turn, provide 120-volt power via an onboard DC-to-AC electrical inverter system.
One important caveat: Inverters are generally more limited in the AC power that they can supply versus a more robust AC generator. Accordingly, this generally limits the primary market for DC generators to boats less than about 55 feet in length overall.
That said, a DC generator can eliminate much of the complicated AC shore-power rigging and provide a seamless transition between the DC and AC systems, says Chad Godwin, OEM sales director for Fischer Panda, which currently offers two diesel-powered DC generators, as well as a full line of AC generators. The 12-volt AGT5 delivers 12 volts at 272 amps and is rated at 5 kW; the AGT6 produces 24/48 volts at 192/96.5 amps and is rated at 5.5 kW. The company also builds custom DC generators for boatbuilders.
Lending impetus to the development of DC generators is the growing use of marine lithium-iron-phosphate (LiFePO4) house batteries, which are lighter in weight, provide greater storage capacity, and recharge faster than traditional lead-acid AGM batteries. “A diesel-powered DC generator represents a near-perfect complement, providing faster, quieter, safer, and more-effective low-rpm charging than most outboard engines can deliver,” Godwin contends.
DC generators also weigh less, require less space, and consume less fuel than AC generators. “The AGT generators can weigh 50 percent less than a comparable AC generator and are up to 30 percent smaller in size,” Godwin says. “Because you don’t have to continuously run a DC generator to power AC accessories, it consumes less fuel than an AC generator.”
In many ways, Fischer Panda’s DC generators are an answer to Navico’s Fathom e-Power system. Instead of a marine generator, Fathom uses high-output alternators in select Mercury outboards to supply DC power to charge a bank of LiFePO4 house batteries. However, outboards need to rev at fairly high rpm to ensure that the battery system can keep up with heavier-load accessories such as an air conditioner. The Fischer Panda AGT6 8.8 hp generator provides an effective alternative when using outboards at low rpm such as when slow-trolling. Of course, the Fischer Panda DC generators require that most boats have a separate diesel-fuel system.
Like the Fathom system, Fischer Panda’s AGT generators also have an automatic feature that monitors a boat’s battery bank and turns on and off in auto mode to keep batteries correctly charged.
These water-cooled generators are also extremely quiet, registering just 66 dB(A) for the AGT6 when measured at a distance of 7 meters, according to Fischer Panda. These lower sound levels, combined with intermittent usage, mean you could conceivably run the generator in a mooring or in an anchorage without unduly annoying your neighboring boaters.
Read Next: AGM vs. Lithium Batteries
The diesel-fuel requirement for the AGT system presents both benefits and drawbacks. On the plus side, diesel exhaust minimizes those dangerous carbon-monoxide fumes associated with gasoline exhaust. On the downside, as pointed out earlier, a fuel tank dedicated to diesel fuel will be needed aboard almost any outboard-powered boat equipped with this generator system.
Fischer Panda is currently supplying DC generators to four boatbuilders for outboard-powered models within each of their lineups. This includes the new Regal 50 SAV, which features the factory-installed DC generator system that it has dubbed “LivePower.”
