All over the internet you will find articles, and reviews about RV’s and power inverters. If you are searching for an inverter it can become quite confusing, and very expensive depending on your setup. To determine what size inverter you will need in watts is a simple multiplication formula, amps times volts. Our Keystone is a 30 amp, so 30 amps x 120 volts = 3,600 watts. Plugged into a 30 amp power outlet we can run all normal AC appliances such as the TV, refrigerator, hot water heater, dehumidifier, lap top, and a few plug in air fresheners. If the air conditioner is running we have to turn off the hot water to run the microwave, toaster oven, or coffee pot otherwise if the hot water kicks on it may, and has tripped the main breaker.
We chose a 3000 watt inverter manufactured by SUNGOLDPOWER. We excluded the air conditioner, obviously we don’t have enough batteries, or solar to run it. We also excluded the electric hot water, and refrigerator, anytime we are running off our inverter these are switched over to run on propane. We sized our inverter based on a normal small appliance load, plus being able to run the microwave and coffee pot (sometimes you forget your not in a house and try to run multiple appliances with no second though). We settled on a 3000 watt inverter, playing with the amps times volts formula to figure that’s a 25 amp output on the 120 volt side of the inverter, slightly under what our Passports AC electrical system is designed for. We could have gotten a smaller inverter but many installations with smaller inverters also require, separate transfer switches, battery chargers, MPPT solar controllers, multiple wiring connections, switches, and circuit protectors. We went with a fully self contained grid tie inverter capable of 25 amps AC output, 90 amps of DC battery charging, 60 amps of MPPT solar charging, and switching from grid to invert mode automatically with no disruption to the power supply. This thing is a beast, it weighs 79 pounds and pulls 12 amps DC with no load other than the internal electronics. If it was loaded to the 3000 watt rating it would pull roughly 250 DC amps, and that’s what we fused it for on the battery terminal, although we may step up to a 300 amp terminal fuse to give a little wiggle room and not blow the fuse now that we have replace the deep cycle lead acid batteries with battle born LiFePO4 lithium deep cycle batteries.
This is not a boondocking friendly inverter if you are just looking at the amp draw without a load, to reduce our DC power usage when large AC appliances are not in use we installed a Wagan 400 watt pure sine wave power inverter, and a (DPDT) double pole double throw relay. This inverter powers the small appliances like the TV, dehumidifier, and plug in air fresheners with no problem and only uses about 7 DC amps to do it.
The circuitry goes like this, 120 volts is supplied to the factory 30 amp shore plug, either by an electrical grid power source, or our 3100 watt champion generator. This wire was disconnected from the factory WFCO converter main breaker, it was ran up to the underbay where our inverter is mounted and terminated to the input breaker of the inverter. The 120 volts then comes through the inverters transfer switch either as line voltage or inverter voltage, goes out the output breaker to the DPDT relay, activates the 120 volt coil closing the normally open contacts and sending the 120 volts back to the WFCO converter panels main breaker and powers all outlets in our travel trailer. If we are boondocking then the big inverter stays in standby mode, the DPDT relay is in the normally closed position and the smaller 400 watt inverter supplies 120 volts to the WFCO main breaker. From the factory the WFCO power converter charger was sharing a breaker with the TV, we installed it on a separate breaker and keep it turned off. You do not want the converter powered from the batteries, this causes a loop loss and will drain your batteries for no reason.
We purchased the Renogy 200 watt solar kit with the standard wanderer controller. The panels were great but the controller not so much so we knew we would probably want to upgrade it in the future. The MPPT charge controller built into our inverter allows us to expand up to 1200 watts worth of solar panels, we have added a plug so we can hook our 100 watt Renogy suitcase panel up to provide a total of 300 watts of solar power. In full sun conditions we will get 15 amps charge from our three panels, during the day when we are out and about not using much power this will recharge our batteries no problem. With the 90 amp charger that is built into our inverter we can fully recharge dead batteries in about two hours, that greatly reduces generator usage in the event we use a lot of power due to cloudy days or just using more power for things. With the WFCO converter from the factory we had to run the generator for about eight hours and still did not get a full recharge on our lead acid batteries.
We wired our inverter with 0000 gauge welding cable, the reason we used such a large wire was voltage drop. 12 volt DC is prone to voltage loss, with our wiring being so large and under five feet we have less than one volt of voltage drop. This is important with recharging the batteries quickly and the inverter getting the power output from the batteries it needs running large loads like the microwave.
Our set up does have one minor quirk, and we have not yet decided on an action plan yet. if we are plugged in, such as when we stay in a campground with hook ups with the air conditioner running, if the pedestal looses power the inverter will swap over to invert mode and the 250 amp DC fuse will blow. This is good otherwise the air conditioner would drain our batteries dead in minutes. Right now when using full hook ups we keep the 3000 watt inverter on standby, line voltage priority, it shuts down when shore power is not available and our camper loses the 120 volts. We keep the 400 watt inverter manually turned off when hooked up. We have considered installing another breaker panel just for items like the air conditioner, and hot water to only have power when shore power is available. We feel this would be going overboard, it would be fairly simple to do but the need considering it’s a rarity does not justify the time or the cost. We keep the refrigerator on auto so if 120 volts is lost it will swap to propane, everything else loosing power for awhile if we are away is not a big deal, we can always reset the microwave clock when the power is back on.