Upgrade to energy independence Page 2
Step 3: Decide on AC Power Sources
Most equipment on boats is designed to run off 12-volt DC power. We do have a few things on Sea Spell, such as a sewing machine and a computer, that require 110-volt AC power. To operate these, we installed a 300-watt inverter to convert DC power into AC power (up to 15 percent of the energy passing through the inverter is lost). An inverter is simple to install.
An alternative is to install a generator. An advantage is that some generators produce AC power directly, eliminating the need to convert DC power to AC when the generator is running. A good-sized generator can produce enough power to run an air conditioner, something most DC systems cannot accommodate, and can also charge DC batteries. An inverter/charger combines both functions; it can change AC power to DC to charge the batteries and then convert the DC power back to AC when the generator is not running.
A good generator can serve as a boat’s primary source of power. In recent years several companies have developed suitcase-size, reliable, efficient, and quiet units. The downside is that you have to buy more fuel and maintain the generator.
Step 4: Select Batteries
The heart of every electrical system is the battery bank. We upgraded our batteries from two mid-size 12-volt batteries to four large 6-volt Trojan batteries connected together to form one extra-large 12-volt bank. The advantage of 6-volt batteries is that they are heavy-duty and mass-produced, so they are less costly than other options. We also have a separate battery for starting our engine. It is kept topped up with a trickle charger attached to the main bank.
There are several varieties of batteries on the market today. Traditional flooded, or wet-cell, batteries require regular checks to top up water levels. Newer sealed AGM (absorbed glass matt) and gel-cell batteries require no maintenance. When being charged, flooded batteries can release explosive hydrogen gases that must be vented. Sealed batteries have a relief valve.
The three types have different charging requirements, so it is important to match your charging regulators to the type of battery you use. Selecting the best batteries for your needs involves weighing the cost, how often you use them, and the conditions they will be subjected to. Some battery types work better in cold (or hot) weather than others.
Whichever battery type you choose, select deep-cycle batteries that can be heavily discharged and recharged many times. Deep-cycle batteries last longer if you don’t discharge them below half of their rated capacity. This means your battery capacity should be at least double your anticipated demand. If you plan to use wind and solar power to help keep your batteries charged, you’ll want to have enough capacity for times when the wind isn’t blowing and the sun isn’t shining—as much as three times the projected demand.