September 25, 2023

TT# 135 Electrical Systems in Future RVs (Part 2)

By: Rob Lowe

The Future of RV Power


In the last TechTip #134, I introduced the concept that the automotive industry is likely to raise the battery voltage from 12 to 48 volts. That, while a big change, is not unexpected, and many would say that it is long overdue.


RVs are moving to an integrated power system especially in smaller Electric Class B’s. Winnebago and Thor’s Airstream have installed a lithium battery system in their coaches and utilize solar power to charge the system much of the time. The main chassis battery powers the EV powertrain, with a single 12-Volt battery powering the control systems. I would expect that as the industry moves to a higher voltage electrical system that the control system battery voltage will move up to the new industry standard (48-volt).     


Augment this transition, with a newer Lithium Battery system option that features far more endurance, substantial weight reduction, and the ability to be installed in non-vented compartments, while adding electronic control systems for many of the RV systems. The additional benefit of modern RV solar systems and improved inverter-chargers, along with the introduction of Electric Vehicles to the marketplace, both for personal transportation and now in smaller RVs has changed the way everyone views the equipment on RVs. Many new components have been updated ranging from RV refrigerators, air conditioners, even methods of cooking that were unheard of just a decade or two ago. It is now a reality that 12-Volt air conditioners already exist. Moving the standard to 48-Volts makes it even more likely that RV air conditioners could be powered by the Coach battery system. While 120VAC from an inverter is the favored approach currently for coaches running equipment requiring AC, inverting is an inefficient method compared to direct power these systems including the air conditioner. If a component is designed for the battery voltage available, the losses incurred in the conversion of power is nulled. We’ve already seen RV compressor refrigerators becoming standard on some RVs after the industry moved to install ‘residential’ refrigerators in RVs. How long will it take RV makers to move to the next major appliance to direct power rather than an inverter?


Government regulation and environmental concerns have brought the reality that portable and built-in generators will be banned within a decade. Combine that with the adoption of RVing as a lifestyle by many younger, more adventurous, connected RVers which see ‘camping’ as being ‘off the grid’. We’ve already begun to see Class B and small Class C RVs planned and some introduced that have no propane fuel on board and some have no need for external power to operate most of the onboard systems. As some of the new vehicles on the road are full Battery-Electric, the RV industry has reacted by developing trailers with a motor and lithium battery power source that can augment the range of the towing vehicle to return its range while towing, to what it has without pulling a trailer. Some smaller RVs are also fully battery-electric models without a gas, propane or diesel fuel source.


The RVIA (the industry body that regulates the standards to which all RVs must comply with), have taken up communications with the Campground Association, owners and the chains (i.e. KOA and others) with the intention of having them provide campsites ready to ‘power’ electric vehicle (EV) towing vehicles and a separate power pedestal for ‘powering’ the towed trailer. I use the word ‘Power’ loosely since these campsites will supply charge power to charge both parts of the RVing experience, the ‘towing’ vehicle and the ‘towed’ vehicle.


OK, where does that leave conventional motorhomes? The future is moving in the direction that most types of RVs will contain a power source with the potential to operate ALL onboard systems. For clarity the RV air conditioning, heating, and water heating, cooking appliances and the refrigerator, along with all lighting and control systems, will be powered by an off-grid onboard, clean power source.


In early 2023, Tesla announced that their new Cybertruck, which will begin deliveries in 2024, will be using a 48-Volt electrical system for all automotive functions. The electric drivetrain will utilize 800 volts. Adoption of such high voltages, greatly reduces the size and volume of wire used to carry the power from the power source to the powered items. This higher voltage also allows a more efficient use of the power to drive major RV systems. In 2023, the automotive and control systems on most ‘on-road’ vehicles are powered by a 12-Volt battery. On EVs, the powertrain has a high voltage battery pack which typically provides 400-800 volts for the drivetrain components, while a separate 12 (or 16-Volt lithium) battery powers all control and automotive systems. It is expected that with Tesla’s decision, all vehicle manufacturers will move their electrical systems to use a power source of 48 Volts. This will reduce the wire size needed for the many automotive systems and increase battery capacity. Alternators and the associated wiring may be smaller. I’d predict that initially in a motorhome RV application it will be common to see two alternators, one for automotive systems and another for the RV electrical system. That is consistent with many chassis makers supplying cutaway chassis to the RV industry, that have forbidden those RV makers from directly connecting to the chassis electrical system. Charging the Coach battery systems requires a battery-to-battery charging system. This system works in reverse when the chassis battery needs to be charged from the coach power source. The use of dual alternators to independently charge the chassis and coach batteries will move to an integrated single power source. This is a natural progression of two separate systems to a single chassis and coach power system that allows all electrical needs to be sourced from a single power source and combining the charging function into one system, as time goes on. That is the approach being taken on early production EV powered RVs,      


At the present time, RVs that have eliminated an onboard generator, have added a second ‘house’ alternator system powered by the engine. This system, when fully integrated, starts the emission-controlled engine as required, to charge the battery, just as an Automatic Generator Start (AGS) system does on newer generator-equipped RVs. With ample modern solar systems, the need to start the vehicle engine is greatly reduced. In addition, as described in more detail in Technical Tip #134, newer alternators are beginning to appear that allow battery charging at much lower engine RPM, even idle speed. As appliances, such as cooktops and air conditioners are re-designed for RV applications, they will most likely be designed to use the RV (coach) system. A source will provide power to maintain the 48-volt ‘chassis’ battery. They will not require 120VAC directly from an inverter or campground pedestal to operate the coach systems. The campsite will provide power to charge the batteries that power all onboard RV systems.


Ultimately, as electrification of motorhomes moves forward, a single power source could power the RV drivetrain as well as the coach systems. This power source will be far more substantial than anything seen on current generation RVs, however by integrating the power source, onboard systems will be less complex and far more durable. The dream of many newer RVers to go ‘off the grid’ will become a reality and campgrounds that are currently a source of reliable power to operate RV systems will become more of a charging station for the integrated power systems on these RVs. Trailers will have their own on-board, substantial, power source and potentially a drivetrain to aid the towing vehicle to maintain the towing vehicle’s range while towing.  Campground power sources will be designed to charge the onboard batteries which will power the drivetrain and the trailer systems. Campgrounds of the future will have to update and maintain a more robust power system, most likely including substantial solar charging systems and updated electrical connections. A powerful future lies ahead for those RV makers ready to take the leap to EV RV’s.


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