Forty years ago, the solid-state revolution, which gave us computers and a host of increasingly powerful electronic devices, reshaped boat energy systems in ways that have underpinned a remarkable transition from camping out to enjoying the comforts of home. Initially, this required an AC generator to be run long hours, and sometimes 24/7, often extraordinarily inefficiently and frequently with a duty cycle that was (and still is on many boats with generators) damaging to the generator engine.
Over the years, three technologies have fused to sideline the generator and today are fueling a new revolution in onboard energy systems.
These are DC-to-AC inverters, lithium-ion batteries, and alternators with levels of output we could only dream about in the past. Inverters can now handle any AC load on a boat, including substantial air conditioning; lithium-ion batteries store the energy needed to power the inverters (and all other boat systems) for hours and sometimes days; and alternators recharge the batteries with limited engine run times, mostly when underway so no additional run time is required.
Inverters are well understood, and lithium-ion batteries are becoming more affordable and widespread—although many more installation issues need to be thought through and accommodated than with lead-acid batteries.
For now, I want to focus on the evolution of alternators.
The Pioneers
How many readers remember Dave Smead? A brilliant engineer, Dave’s many accomplishments include building the world’s first portable digital voltmeter for the U.S. Air Force in the 1960s and creating satellite communications networks for NASA in the 1980s.
In 1983 he sailed from Seattle to Mexico where he met Ruth Ishihara, and they returned to Seattle via Hawaii. Dave realized the cruising community was hopelessly uninformed about battery systems and onboard energy management. He shifted gears into creating effective energy systems for cruising boats.
Dave is the principal reason we have high output alternators with “smart” regulators and sophisticated energy monitoring. He and Ruth founded Ample Power Company to bring cutting edge products to market. Their book, Living on 12 Volts with Ample Power, taught many of us how to manage batteries to optimize performance and life.
Ample Power delivered ever more advanced alternators, regulators, and systems monitors until 2017 when Dave went into cardiac arrest on the first lap of a motocross race. All of us who disconnect from shorepower and continue to enjoy comfortable onboard lifestyles owe a debt of gratitude to the largely unrecognized genius who was Dave Smead.
The Seattle to which Dave and Ruth returned in the 1980s was a hotbed of innovation. Bill and Connie Montgomery founded Balmar. Rick Proctor launched Cruising Equipment Company. A group of innovative engineers playing musical chairs founded Heart Interface, Trace, and Statpower, the three leading inverter companies. Then Xantrex bought all but Balmar, made a series of strategic mistakes, and opened the door to European upstarts Victron and Mastervolt.
Balmar emerged as the clear leader in the high output alternator and smart regulator marketplace.
Initially Balmar marinized automotive alternators. The typical automotive alternator is, at best, 60% efficient. This means 40% or more of the input energy supplied by the drive belt is converted to heat. The higher the output of an alternator, the greater the heat. Conventional alternators are likely to burn out if run hard at full rated output for extended periods of time.
There are three ways to address this heating: improve the cooling, improve the efficiency (the higher the efficiency for a given level of output, the less the heat generated), and cut back the alternator’s output as the temperature rises. Balmar has implemented all three. Whereas most alternators have a single cooling fan at the pulley end, many Balmars have a fan at both ends. Balmar has steadily upped efficiency, first with something known as hairpin stator windings and later with braided stator windings. There is an option to add a temperature sensor to the back of all Balmar alternators, enabling the alternator’s output to be controlled on temperature as well as voltage.
Controllers
On the control side, a huge improvement in functionality came with the introduction of multistep regulators. The initial three steps—bulk, absorption, and float—common to all these regulators have been refined to incorporate algorithms that optimize the performance of a wide range of battery types, including lithium-ion. Battery bank temperature measurement and compensation is almost universally applied, and frequently alternator temperature compensation. A succession of Balmar voltage regulators have dominated this marketplace.
In 2014, Bill and Connie sold Balmar to CDI Electronics in Alabama. The move resulted in the loss of some of the Seattle-based talent, spawning Wakespeed, a company founded by Rick Jones and Al Thomason. Rick and Al embarked on an ambitious program of regulator development incorporating additional parameters into the control process, notably the ability to manage an alternator based on available engine power. The resulting Wakespeed WS500 regulator has become the one to beat. In 2022, lithium-ion battery manufacturer Battle Born bought Wakespeed.
Upping the Power Levels
Why the need to incorporate engine data into an alternator controller? When installed on relatively small engines, for example the 40-hp engines found in each hull on many cruising catamarans, the ever more powerful alternators can overload engines at certain points of operation, especially at wide open throttle.
How powerful are these alternators? The rated output of an alternator is typically given in amps. In the days when DC systems were all at 12 volts, this made it easy to compare one alternator with another. But now we also have 24 volts and increasingly 48 volts. A 12-volt, 150-amp alternator produces half the output power of a 24-volt, 150-amp alternator. To compare power levels, we must factor in the voltage to derive watts (W). The 12-volt, 150-amp alternator has an output of 12 volts times 150 amps, or 1,800 watts. The 24-volt, 150-amp alternator has an output of 24 volts times 150 amps, or 3,600 watts. We generally divide the watts by 1,000 to derive kilowatts (kW)—1,800 watts equals 1.8 kW; 3,600 watts equals 3.6 kW.
It is not uncommon to find small frame alternators (interchangeable with most alternators that come with an engine) with rated outputs up to 3 kW. American Power Systems (APS), a Balmar competitor, has some rated at over 5 kW. Balmar and APS have large frame alternators rated at up to 7 kW. APS has a small frame, 48-volt alternator rated at up to 10 kW. Let’s say this alternator is 70% efficient. The power into the alternator (from the drive belt) needs to be (10 kW/0.7) equals 14+ kW. This translates into almost 20 hp.
Now you can see why we need to incorporate engine power levels into alternator control, especially as wide open throttle is approached!
Speed Issue
As impressive as some of these alternator outputs seem to be, there is a fly in the ointment. Alternators can be wound and internally wired in different ways to either optimize the rate at which the alternator builds its output (i.e., how fast the amps climb as speed is increased) or to maximize the output at high alternator speeds. You generally can’t have both. The super-high-output small frame APS alternators must be run at relatively high speeds before they will produce any output at all, and at speeds that are often not seen in boating applications if they are to reach their full rated output.
Balmar has two almost identical medium-case 48V alternators—one is rated at 5 kW, and the other at 3 kW. One is optimized for maximum power at high speed (5 kW); the other can deliver about 2 kW at idle speeds but tops out at 3 kW. In many applications, the faster ramp-up and lower maximum rated 3 kW alternator will deliver more energy to the boat than the higher speed, higher rated 5 kW alternator.
Which brings me to the Integrel alternator, but first a digression. In 2008 I helped to secure a $3 million grant from the European Union to investigate the applicability of automotive hybrid technologies to recreational boating. We conducted four years of testing of electric motors, motor controllers, and generators. We demonstrated, from a propulsion perspective, that it is hard to make marine hybrids more efficient than a well installed diesel engine. This is not the outcome we expected!
However, I concluded we could greatly improve the efficiency of house energy systems. In 2014, I persuaded the Parker Hannifin corporation to explore my ideas. Under the leadership of Steve Knight, business unit manager for Parker Energy Systems, we engaged in a new round of multiyear product development.
The Integrel System and 48 Volts
We had three core alternator objectives: high output power levels (15 kW), high levels of efficiency (80+%), and a fast ramp-up in output.
We experimented with a liquid-cooled, permanent magnet alternator. We hit the targets but at considerable expense and with the added complication and maintenance of the cooling circuit. Then Steve discovered an air-cooled alternator that combined permanent magnets with a conventional alternator. Although we achieved outputs of 13 kW with an early version, we scaled back the objective to about 8 kW and focused on achieving a rapid ramp-up with better than 80% levels of efficiency.
Over the next three years we tested different versions of the device in the laboratory and in my Malo 46, Nada, until we achieved the desired results. There is currently nothing in the market that comes close to the Integrel system in terms of performance. (Full disclosure: I still have a small stake—less than 5%—in Integrel Solutions, the company that now produces and sells the system.)
But, this system has required more changes. If we operate at the power levels of the Integrel alternator based on a 12-volt system, the amperage would go through the roof (8 kW at 12 volts equals 667 amps). There are no conductors in the recreational boat world big enough to carry the amps, and 24 volts would still be pushing the limits of available conductors.
We decided to go to 48 volts and limit the system to 170 amps, which raises the question: How to power 12-volt and 24-volt devices on a boat? Easily. Widely available DC-to-DC converters, battery-to-battery chargers, and other devices can step down the 48 volts to 24 volts and 12 volts. Efficiency levels are well above 90%.
There are significant benefits, especially in conductor size reductions and often also efficiency, to running the high current devices on a boat at 48 volts rather than 12 or 24 volts. When we initiated the Integrel project, there was no 48-volt equipment. Today there are alternators, bow thrusters, windlasses, winches, watermakers, air conditioners, and inverters. The 48-volt platform is gaining traction.
A Qualitative Step Forward
From my perspective, the maturation we are seeing around impressively powerful alternators, lithium-ion batteries, sophisticated energy management systems, powerful inverters, and a 48-volt platform represents more than a quantitative improvement in our onboard energy systems. I see it as a qualitative improvement; when we look back on it in years to come, we will place it on a par with the solid state revolution of the 1970s. That revolution ushered in the possibility of enjoying the comforts of home on board; the current one is bringing this to fruition without the need to have a generator, and, in most cases, without additional engine run time over what we need for propulsion.
On my own boat, in the time it takes to get into or out of a slip or to set the anchor or pull it back up, we can create and store sufficient energy to run Nada for at least 24 hours. And when underway, even after six years with the Integrel system, it still puts a smile on my face when I see 8 kW of output being pumped into my lithium-ion battery bank. This is such a far cry from that first high output alternator system I installed 40 years ago.
Alternator Testing
The rating of alternators is a minefield. The standard rating process is something called a sweep test. The alternator is quickly accelerated from no speed to full speed with the maximum output, in amps, logged at all speeds. The ambient temperature is 25°C (77°F). The alternator is not run long enough to heat up. The result is a level of output that will never be seen in practice.
A more realistic test is to hold the alternator at any given speed and level of output until its temperature stabilizes. This is called a saturated dwell test. It is frequently conducted once again at an ambient temperature of 25°C. Even so, the output will be substantially below that of the sweep test, by as much as 20%.
An even more realistic test is to do a saturated dwell test in a high ambient temperature. Given that the temperature alongside an engine is commonly as high as 90°C (194°F), this would be an ideal ambient for conducting the test. The only data I have seen for such a test comes from APS, and is based on an ambient temperature of 100°C (212°F). I have also seen data from Balmar for a couple of their alternators based on an ambient temperature of 75°C (167°F).
The bottom line: Most alternator output data can be substantially discounted in terms of real-world performance. The closer the data is to low ambient temperature sweep data, the more it can be discounted.
January/February 2024
