Boats, small cabins, and portable power stations often have just a few small AC loads. Some may have DC lighting, a fridge, and other appliances, but there are a lot of appliances that won’t run on DC.
Some off-grid inverters are made specifically for mobile applications—that is, designed to be less prone to damage from vibration and dirt/dust. They also have an internal transfer switch that removes the AC neutral-to-ground bond when connected to shore power. The smallest of these inverters often don’t have much, if anything, to program; they don’t usually include AC battery chargers or battery monitors, either.
Choosing the correct size is similar to larger stand-alone inverters: the inverter needs to have enough power to run all of the AC loads, and have the correct DC battery voltage. Most models are 12 or 24 VDC. Since these smaller inverters tend not to be used for motor loads, often they don’t have much surge capability.
Models less than about 500 watts tend to have a cigar-lighter plug for the DC connection. Larger units need to be hard-wired into the system. Most have one to two 120 V AC outlets, and built-in fuses to protect the output circuits.
The more economical models may be modified sine-wave, although pure sine-wave models are available. It is important to match inverter power quality with the loads—i.e., don’t use a modified sine-wave inverter on sensitive AC loads, like high-quality audio and video electronics. Some inverters have a built-in LVD, but be sure to look at the actual disconnect voltage since often this feature is at a preset (and unchangeable) very low-voltage disconnection (10.5 V is common)—not for protecting the batteries, but to protect the electronics inside the inverter from low input voltage.
Exeltech’s XP stand-alone inverter. [exeltech.com]
Morningstar’s SureSine inverter. [morningstarcorp.com]