Perhaps the most significant change in this project is the use of a 48-volt battery bank. There are a number of reasons for this, and we’re going to discuss them before looking at a new configuration. Here though, we’re going to start with why we have what we have: an electrical system designed around 6 flooded lead acid cells in series–commonly referred to as a 12-volt battery.
While travel trailers have been around quite some time, the motorhome industry really didn’t get going until the late 1950s. The automotive industry had adopted 12-volt batteries during that decade, switching from 6 volt batteries, for a number of reasons. By going from 6 to 12 volts, or from 3 to 6 flooded lead acid cells, automakers were better able to accommodate increased electrical demands as cars became more advanced. Air conditioning, more powerful lighting, electric windshield wipers, and radios were becoming more common. The switch in the automotive industry also largely enabled the switch from generators to alternators, which are cheaper, more reliable, and more efficient.
If the chassis on a motorhome or the vehicle towing and RV had a 12-volt electrical system, it made a lot of sense to use the same for the RV systems. An alternator could power all the necessary stuff to move on down the road, as well as charge house batteries. Battery systems could be coupled together or traded out in a pinch. In an era where the biggest demands on the house batteries were lights, a furnace blower, and a water pump, a 12-volt battery did the job just fine.
As our lives got more complex, we started wanting to be able to operate certain things while away from shore power. That included some things (like TVs) that could be made to run directly from a 12-volt battery, but others meant that we started seeing inverters installed so we could operate other household devices–small cooking appliances, chargers for battery-powered electronics, computers, etc. It’s not at all uncommon to see a mainstream motorhome today with a 3kW inverter on board, capable of running a microwave, hair dryer, crock pot, or toaster for a limited time.
Ultimately, we arrived at 12V largely because it was shared with the automotive systems we were already using. It was a voltage high enough to do the job in a reasonable manner, and no higher. But as we go to higher power systems, some things start to get difficult. We’ll talk about that next.