ears ago, having a inverter capable of providing maybe 150 watts of modified sine wave power was almost a novelty. I remember my first 100-watt inverter. It was packed inside a bulky aluminum housing and powered a small black and white TV (also a bit of a novelty for those of us who turned to RVing as an outlet for leaving our daily routines behind). Today, inverters are becoming standard equipment on many RVs — and combined with a powerful, smart battery charging circuit, are becoming indispensable, especially for those RVs equipped with residential refrigerators.
In fact, sophisticated inverter/chargers capable of conditioning lithium batteries and part of high-tech packages that run just about everything in an RV — sans an umbilical cord — are all the rage these days for those who relish boondocking. Many larger systems can even run air-conditioners, eliminating the need for noisy generators. The more elaborate systems will have a large 3,000-watt pure sine inverter, a big bank of lithium batteries and a significant array of solar panels.
But while most of the inverters on the market have decent lifespans, higher dependency on off-grid power can lead to inopportune inverter malfunctions — which can pretty much render the 120-volt AC electrical system kaput when camping without hookups and/or running the generator all the time. That’s exactly what happened to the owners of this 40-foot diesel pusher motorhome. And, as expected, it happened during an inopportune time: while on their way to their winter destination.
Xantex prides itself in being RV power solutions company. The Canadian-based entity offers inverter/chargers, control panels, solar systems, lithium batteries and a bunch of other accessories that make swapping equipment relatively easy — and just about everything the company makes benefits from advanced technology. For this project, the Freedom SW 3012 made the most sense, since the motorhome was wired with dual outputs through two breakers. This inverter/charger requires two 120-volt AC inputs, typically arranged in a 120/240-volt AC configuration to distribute the load on both sides of a 50-amp RV service provided by RV site hookups (which is also 120/240 volts AC). In the motorhome, these inputs were protected by 30-amp breakers labeled “Charger 1” and “Charger 2.” The 10-gauge wires from these breakers were routed into the inverter cabinet and were readily identifiable with a multimeter; the neutrals were grounded.
The output terminals of the Xantrex inverter/charger are labeled L1 and N1, and L2 and N2, respectively. They connect to a sub-panel with an un-grounded neutral bar. In the case of this motorhome, the sub-panel is an integral but isolated part of the main AC panel. The inverter output breakers are labeled “Inverter 1” and “Inverter 2.” The output of the inverter connects to each of the breakers, respectively; the neutrals are both connected to the sub-panel neutral bar and the grounds are connected to the chassis ground. Power to the sub-panel is either supplied directly by the inverter or by flow-through from shore power or the generator.
The first step was making sure the incoming power was disconnected from all sources, the breakers closed and the cables from the battery bank removed. As each wire was removed from the existing inverter, the ends were identified and marked. Once the original inverter was free from the cables and wires, it was unbolted and removed and the compartment cleaned thoroughly. These inverters are heavy, so enlist some help if needed.
In order to simplify the process, we surveyed the install strategy and did as much as we could on the tailgate of the pickup that was towed behind the motorhome. We decided to use ¾-inch nylon liquid-tight Type B fittings for routing the wiring through the knockouts in the side of the inverter. It was a good idea at the time, but in the end we were not able to route the wiring without removing these fittings and pulling with a needle-nose pliers. And, working space to tighten the flat nuts was very tight, requiring a few choice words to get these fittings removed and reinstalled, but we got there.
Before mounting the inverter permanently, the wiring for the battery temperature sensor had to be run, which turned out to be the hardest part of the job. We first removed the old sensor and cut and pulled most of the cable for discarding. Routing the new cable requires some engine compartment calisthenics (and, admittedly, more choice language). Fortunately, we were able to grab just enough of the old cable to attach the end of the new one and fish it through the back wall in the inverter compartment. Any loose wire was cable-tied in place, being careful to route around any obstructions and hot zones.
Before moving to the cockpit of the motorhome to install the remote panel, we tested the wiring again, flipped the breakers and confirmed that the output was indeed working as designed and checked for charging current.
The original inverter/charger’s remote panel was removed in order to pull the cable needed to hook up the new Xantrex panel. After marking the cutting zone with another Xantrex-supplied template, a hole was made in the wood panel inside the access compartment above the passenger seat. We used a jig saw, but an oscillating tool could have also been called into service here. The network cable adapter pigtail from Xantrex made short work of connecting the new remote panel — no muss, no fuss, no wire crimping and no guesswork.
Xantrex’s System Control Panel (remote) allows the user to monitor function as well as make parameter changes, which is important, for example, when connecting the inverter/charger to lithium batteries. The substantial instruction booklet guides the user through the steps and provides great insight for monitoring and understanding the various functions.
This unit offers state-of-the art pure sine wave power, so sensitive electronics will be safe, and longer surge times allow operation of motor loads and other high current items like hot plates and coffee pots. Three-stage smart charging is supported by a 100-amp rating. Retail price of the Freedom SW 3012 is $2,698; the System Control Panel has a $314 price tag and the Telephone to CATS cable adapter pigtails are $39 for two.
Living in an RV without an inverter these days is like driving without wheels. Making 120-volt AC power from a battery bank brings off-grid living to a level where compromising is no longer necessary. Harness the sun to keep batteries conditioned and tie them into an inverter, and RVers can enjoy boondocking like never before.
