Boaters are continually looking for their onboard experience to rival the conveniences found in their homes and even in their cars and trucks. That means keeping a boat’s batteries fed to meet demand and, in some cases, converting DC power to AC to run appliances like microwave ovens.
“Battery chargers for boats are purpose-built and are intended to live in the marine environment, which includes salt air,” said David Sell, president of Integrated Marine Systems in Newport Beach, Calif. “They also need protection from spark and negative electrical feedback.”
A marine inverter takes DC power from a boat’s batteries and converts it into AC power so you can use “household” items on a boat without it being hooked up to shore power or requiring the expense of a generator.
Integrated Marine Systems specializes in aftermarket upgrades to boats and yachts. When the company installs a charger or inverter, it uses products from Victron Energy. Solar panels are also becoming more popular for providing recharging power, but they don’t have the capacity to run a collection of appliances. Other popular brands of chargers and inverters include Noco, ProMariner, Attwood, Guest, Xantrex and MasterVolt.
“Victron has a diverse and wide product line that covers charging, power inverting and solar,” said Sell. Victron also has an app that lets an owner monitor the battery bank’s health remotely. “There’s quite a bit of intelligence in those devices that are funneled through the app,” he added, “so you can monitor status and make changes.”
Charger Types
For battery chargers, Sell said 40- and 60-amp units are Integrated Marine’s most popular for 12- and 24-volt batteries. The higher the amperage rating, the faster a charger restores a battery’s capacity.
On the West Marine website, an article entitled “How to Choose a Battery Charger for Your Boat” points out three main unit types a boat owner should consider: portable and onboard, vented and waterproof.
Portable chargers are good for smaller boats. They can range from 1- and 2-amp battery maintainers to 30-amp units that provide a fast charge. These are good for trailered boats because there’s no concern about the charger encountering moisture in a marine environment.
A waterproof onboard charger is designed for a bass boat or other vessel with an open deck plan. They are designed to charge each battery individually, even if they are wired in series or in parallel. Because it’s waterproof, this type of charger is sealed so it can’t dissipate heat that builds up when charging. This makes a waterproof unit a less-than-ideal choice for powering continuous loads and meeting charging requirements of larger yachts. They should be limited to applications for battery group sizes of less than 31.
For bigger boats, vented onboard chargers are used to power continuous loads at the dock and can meet the charging needs of cruisers and yachts. They mount in a dry location and work with a shore power connection and AC distribution/breaker panels. Vented units can handle heavier capacity batteries and/or charge the batteries while they are under load. The vented design lets them dissipate heat generated during charging. Some even have cooling fans.
West Marine described “smart” chargers as units with customized charging profiles based on the type of battery chemistries including flooded, gel, AGM and the newer Lithium. They adjust the charging voltage and current based on the state of the battery. This ensures optimal charging without overcharging, which shortens battery life. Smart chargers can also use a multi-state charging process including bulk, absorption and float stages. In maintenance mode, a charger switches to a lower voltage once a battery is fully charged.
Understanding Inverters
Three main numbers define an inverter and the batteries to which you’re connecting. “The equation is extremely inefficient,” said Sell. “It takes a lot of DC power to create AC power.”
When determining an inverter choice, a boat owner should consider the voltage of the battery bank and the wattage of all the devices you want to power. For example, Victron offers a 12-volt, 3000-watt, 30-amp inverter charger that outputs 120 volts to the host vessel’s electrical panel. It’s called the Multiplus and for a price of about $1,000, it’s targeted for boats larger than 40 feet. “The relationship between the cost of the inverter charger is not relevant to the size of the boat,” said Sell. “Its capacity determines its price.”
He said that appliances like microwaves, icemakers and chiller units for air conditioning systems are usually AC, while a refrigerator can be AC or DC and an inverter will recognize the power requirement and adjust automatically. In homes or boats, any device that changes the climate or temperature draws the most power.
Sell recommends a combination charger/inverter because the device is only about 20% more than buying the two devices separately, it takes up less space and eliminates the complexity of having to connect the two.
“It puts one box in the place of two,” he said. “You’re going to have to spend that money and more to manage the connectivity between the charger and the inverter.”
Marine Integrated Systems also recommends a Dock Boost Transformer for boat owners who like to travel to new locations and use transient slips. “Boaters visiting marinas assume the shorepower is going to be fine and that is absolutely wrong,” said Sell. The transformer is made by a company called ASEA in Huntington Beach, Calif., and has a retail price of $11,500.
The dock boost transformer is a scale-able product that manages and isolates incoming voltage to prevent spikes or sags in power coming into the shorepower, protecting the boat’s electrical panel and infrastructure.
“This is a high-quality way to manage incoming power against those spikes and against the sags in power,” said Sell. “When a spike occurs, it absorbs the surge and when a dip occurs the boat doesn’t know it happened.”
