Inverters 101:

We are going to explore that common question to so many RV owners: “What in the blazes is an inverter and do I leave it on all the time?”

The inverter is another tool available to maintain the batteries, because even those of you who keep that battery bank primed and preened will still require assistance to charge those batteries, as well as turn DC power into 120-Volt AC to operate various appliances. The RV inverter does both.

Do you ever notice that the moment you turn on the television, power is instantly engaged? This is due to the fact that even while the television is off it is using a small amount of electrical power to sustain a “standby” mode. That small amount of power is considered a parasitic load, and many electronics in the RV continuously use power in this way. The inverter, when left in the on position and not hooked to shore power, will itself draw about one amp of power, similar to burning a small halogen light. However, when you add the inverter to all those parasitic loads, you end up with an amp draw comparable to five or six halogen lights. So leave the inverter off if nobody is watching television or using the microwave. The only exception is for those of you with an all-electric RV, who should keep the inverter on at all times. However, every coach in storage that is not plugged in should have the inverter remote button, as well as the battery disconnects and house power, turned off.

There’s no shame in pulling off the highway and immediately busying ourselves with the ancient ritual of “setting up camp.” It’s human nature, even when we know the batteries are in a low state of charge, to get the evening underway after all those hours of driving. Plug into shore power, or start the generator. Sometimes it’s even a good idea to do both in case you run into a low shore power supply. Look at a standard 50-amp plug. Four prongs are available that make up “hot 1,” “hot 2,” “neutral” and “ground.” This system of two “hots” makes the available power add up to 100-amps maximum, or 80-amps continuous. Adapting to a 30-amp plug, you will find three prongs that supply “hot,” “neutral,” and “ground,” resulting in a true 30-amps of power maximum, or 24-amps continuous. Comparing the two amperages side-by-side, there is actually a loss of 70-amps maximum when dropping from 50-amp to 30-amp. Firing up the generator while plugged into shore power will give the generator priority, assuring you that 50-amp power is being supplied to the RV.

Once the electrical juice starts to flow, the inverter automatically begins charging the house batteries. Now, on occasion, when the batteries are in a low state of charge, and the inverter is working diligently to charge those batteries back up, breakers may trip as loads are applied when hooked to 30-amp service. This is where the road splits on different model inverters. In some instances, you will find it necessary to simply reduce the loads using the programming features of the inverter remote panel and give the batteries time to charge. For how long strictly depends on how low of a charge the batteries have reached. If your inverter remote panel offers power settings, and you select the appropriate button, charge to the battery can be reduced to enable you to run larger loads. Other model inverters now allow the operator to turn the battery charge completely off. However, in any situation it is important to get those batteries back up to charge and the inverter should be allowed to perform this task at the soonest opportunity.

Time required to complete a battery charging cycle is dependent on the state of charge of your particular batteries and loads that are running concurrently to the charging cycle. Outdoor ambient temperature will also affect battery charging. In some instances you may be drawing out almost as much power as the inverter is working to put in, and this will create a longer charging cycle because of loads applied to the house batteries. Determining actual percent of charge through the inverter panel will require that you factor in what is presently being used. For a general charging goal, calculate that with all electrical loads off, 12.6 to 12.7 can be considered a good charge for the batteries. By reading the inverter panel you can get a ballpark figure of the load going out, as well as the charge coming in, but should always be aware that some of that power is being reduced by distance of travel through the wires. Just like you can’t force a horse to drink, you can’t force a battery to take unnecessary charge. Particularly if the battery has a bad cell, low water or excess corrosion. Inverter programming will not overcharge the batteries. Once charge is completed, additional electrical power is held in float for future use.

If AC power spikes, and your RV is not equipped with a surge protector, most electronic appliances will also spike. Too much of that activity and the circuit boards in many electrical fed components will start limping along like battle-worn soldiers. How do you know if you already have a factory-equipped surge protector? Check next to the transfer switch for a small box with indicator lights labeled Leviton. If you don’t have that box, consider equipping your RV with a quality surge protector. Two types are available, those you plug onto the end of your shore power cord, or those hard wired to the electrical system. While the plug in type is less expensive, it also adds one more cord for you to track. Surge protectors hard wired to your system will be a permanent addition to the RV and less likely to be lost or stolen.

By now you should have a pretty clear picture of the functions of the inverter. However, there is an additional aspect to this component that generates more controversy than a government proposed tax increase. It is called ‘equalize charge,’ and with it, batteries provide power by pulling substance through plates. Unless conditions are always optimum, this substance will sulfate on those plates to create a blockage, which over time will render a battery useless. Cleaning off those plates requires a process of “boiling” the batteries to heat up the plates and knock off the sulfur, known as equalize charge. When to equalize charge is based on your personal battery discharge rate, but never more than twice each year.

Controversy arises due to the fact that the equalize charge process can be confusing. Not all battery types are appropriate for this high-voltage recharging process and it will be necessary for you to determine if your batteries can even undergo equalize charge. If so, you must first remove all loads from the batteries, and it may be difficult to determine what exactly that includes. Even when shutting off the disconnect switch at the batteries, your RV may include other components, added after purchase, that were not directly wired to the original system. Secondly, time is crucial during the equalize charge cycle requiring that you stand by ready to shut down the system immediately upon completion. If you want to equalize charge, and can confirm that all loads are disconnected, fill the batteries with the appropriate amount of distilled water, loosen the battery caps and engage the Equalize Charge feature on the inverter panel. Refer to the inverter’s operating manual for specifics on the equalize charge process. During this cycle, the water in the batteries will begin to bubble rapidly, and as soon as the battery case becomes too hot to hold your hand against, turn off the equalize charge feature.

The time it takes to complete the equalize charge process varies and requires continual monitoring. Two to three hours is not uncommon. Throughout this process the batteries must be well ventilated, requiring that the battery slide tray be completely opened. During high charging rate, batteries will gas in extreme amounts. This gas is flammable and can cause potential damage to the paint on the RV. You may find it helpful to place an old towel over the batteries, as well as keeping a supply of rags on hand to mop up the spills. This substance is hazardous and any implements used during equalize charge should be disposed of in a safe manner. Remember that any time you work around the batteries you should remove all jewelry, including watches and rings, and wear safety glasses, durable clothing and rubber gloves. Some batteries are not designed for equalize charge. For safety’s sake, you may find it desirable to have the process performed by an experienced technician, or simply replace the bank with new batteries.

Inverter remote panels are located in various locations due to different model coaches. When the system is activated a green or red LED light is on. If the light blinks, or goes into standby, the system is monitoring power from another AC source and will kick in when needed. Leaving the inverter on for back up power is fine, but always be aware of continuous battery draw when the inverter is on. The push button pad switches on the inverter panel are delicate, designed with a slight delay before the indicator light comes on. Touch and release the push button quickly. If you hold down, waiting for the light, the system may actually go through a cycle of on/off/on/off, causing you to think the panel is malfunctioning.

So the mystery is solved. Keep an eye on the wall panel to monitor the condition of your batteries and the inverter will become a valuable tool in helping you to efficiently manage your RV electrical system. Monitor the electrical loads, maintain the batteries, use the inverter when needed, and you will find a valuable ally in prolonging the life of the RV batteries.