A Mad Scientist’s Take on the Ultimate Electrical System (Part 1)

Designing the Ultimate Electrical System For Truck Camper Rigs

In previous electrical and solar power articles published by Truck Camper Adventure, we purposely simplified the systems and terminology to make it easier for novices to understand. In this article, written by Pat Davitt, we’ve taken the opposite approach by presenting an advanced article with an advanced solar power system design for those who are more technically savvy. But beware, Pat’s approach to electrical system design isn’t cheap, primarily because of the batteries. If you’re new to RVs and truck campers, and you’re interested in learning more about batteries and solar power, we recommend that you take a look at our Building a Great Solar Powered Truck Camper Rig article.

Months ago, during what must have been a “senior moment,” I decided to explore buying a truck camper. It couldn’t have been a mid-life crisis, since I went through that glorious time about 20 years ago. I’m familiar with camping either by walking or with horses and/or mules. As my research progressed, it became apparent that I wasn’t going to be happy with the electrical systems. So, I put on my Systems Architect hat and decided to design my own.  Talk about things rapidly getting out of hand.

I don’t claim to be a truck camper expert, just the opposite, I don’t own one yet. I have, however, been in or, looked inside of one, a few times. This lack of knowledge may be a good thing since I have no preconceived notion of the “way it should be.” Living in an off-grid solar home for the last six years and, at another time in my life, living on a motor vessel with extensive AC and DC circuits brings helpful insight to the design process.

The two important things to remember are:

The purpose of this prototype project is to push the limit of electrical power that can be installed in a camper. I’m not concerned about if one “needs” the power, but rather “how much will fit.”

The engineering intent is to have all the electrical equipment/components, except for the batteries and solar panels, in a single enclosure. And, that all external connections, including load circuits, solar panels, batteries, etc., will be made on the exterior of the enclosure. The goal is to have a pre-built electrical enclosure that can be installed, as a unit, in a camper. Even though I’m “going large,” this concept can be downsized to fit smaller equipment and campers.

Part one of this article is an introduction and the design process, part two will be the technical information and, part three will be my thoughts on where the future may lead.

I knew, from my research, that for a system to work in a truck camper, or any RV for that matter, it must be small and light weight. The design criteria are:

  • Maximize Solar Panel Wattage
  • A powerful, yet lightweight, 48 volt Battery System
  • AC Power to run an induction cooktop, convection microwave, and air conditioner
  • DC Power to run Danfoss Refrigerator, Pumps, LPG Furnace and Water Heater, Ventilation, and LED lighting
  • 50 amp 120 volt 6,000 watt shore power/generator capabilities (Not 120/240 volts)
  • 48 volt Solar Charge Controller and Inverter/Charger
  • High quality components Installed in a single electrical cabinet
  • Meet ABYC (American Boat and Yacht Council) Standards
  • Cost not as Important as functionality

Design Sequence

1. How much Solar wattage can I put on the roof? An 8.5-foot cabover camper should have roof dimensions of about 7 feet wide by 13.5 feet long. With the proper rack, four 36 volt 350 watt panels will fit with a couple of feet left over for a vent fan. That gives me a total of 1,400 watts of solar. It will also require a non-rooftop mount air conditioner.

2. Batteries: The smallest, lightest, and most powerful batteries I found were Victron Lithium-Ion HE. They are 24 volt 200 amp hour, 7.6 inches wide by 14 inches long by 14.25 inches high, and weigh 63 pounds apiece. Two of them in series will give me 200 amp hours at 48 volts. That equates to 7,680 usable watt hours assuming a maximum 80 percent Depth of Discharge (DOD) (48 x 200 x .8). Their Cycle Life is 2,000 at 80 percent DOD. These batteries are Lithium Nickle Manganese Cobalt Oxide (LiNiMnCoO2) and weigh about half as much as the more popular Lithium Iron Phosphate (LiFePO4).  The Victron’s also have a data feed directly into the control/monitoring computer (more on this later).

Just for grins I figured out what it would take to equal 7,680 usable watt hours with Lifeline GPL-27T AGM 12 volt 100 amp hour batteries. Each battery has (12 x 100 x .5 = 600) or 600 usable watt hours assuming a 50 percent DOD. Divide 7,680 by 600 and you get 12.8; it would take 13 of the Lifelines to equal the usable watt hours of the lithium’s. Also, the Lifelines weight 62 pounds apiece, so 13 of them weigh in at 806 lbs. vs. the Victron’s 126 pounds; not to mention how much space they would need. The cycle life of the Lifeline batteries is about 1,000 at 50 percent DOD.

The downside of the Victron lithium’s, with the required Victron BMS, is the initial expense. The retail cost for two batteries and the BMS is $10,770, with the batteries making up $8,800 of that total. But then 13 Lifelines would cost you about $4,200 and they have half the cycle life of the Victron’s. So, the TCO (Total Cost of Ownership) over the expected lifetime of the two battery types, is about even. That surprised me.

3. Core Components: (Solar Charge Controller, Inverter/Charger, Control and Monitoring Device). The Victron components I chose were:

  • Quattro 48/5000/70-100/100 120 volts – Inverter/Charger
  • Blue Solar 150/45-tr – 48 volts Solar Charge Controller
  • Lynx Ion BMS 1000 – Battery Management System
  • Color Control GX – System Setup, Management, and Control PLC
  • Two Victron HE 24 volts/200 amp hour Batteries

4. AC/DC Panels and Load Centers:

  • MidNite Solar MNDC 175 – DC Load Center
  • Blue Sea Custom DC Distribution Panel
  • Blue Sea Custom AC Load Center/Distribution Panel

5. Solar Panels: Four 350 watt 36 volt LG Solar NeON R LG350Q1CA5 PV Panels

6. Miscellaneous Equipment:

  • Mean Well HRP-600-12 – Industrial Grade 120 volts AC to 12 volts DC 50 amp Power Supply
  • CUI PYB10-Q48-S12-DIN – Industrial Grade 10 watts 48 volts DC/12 volts DC Converter

Obvious Questions

1. Why a 48 volt DC Battery System? Part of it is familiarity with 48 volt systems, I have one in my house. The main reason is, that when you get into high power designs, the size of things really matters. The batteries I’m using have a maximum discharge current, that is fuse and breaker limited to 200 amps at 48 volts, that’s equivalent to 800 amps at 12 volts. The size of wires, circuit breakers, fuses, and other components becomes prohibitive at these power levels. The only down side to a 48 volt system is the requirement for a 48 volts DC to 12 volts DC converter to power the loads. Or, as I have chosen to use, a 120 volts AC/12 volts DC 50 amp power supply.

2. Why did I choose to supply power to the DC loads from an AC/DC Power Supply? I had a heated argument, with myself, about that, but finally decided to go the AC/DC route. It has to do with redundancy. If I power the DC from an AC source, and have a problem with the batteries or inverter/charger, I can still have full DC and AC power by connecting to either shore power or a generator. Also, the AC/DC Power Supply is more efficient than the DC/DC Converter.

3. Why did I choose a 50 amp/120 volt/6000 watt service instead of a 50 amp/120-240 volt/12000 watt service? I was trying to avoid the complexity of split phase, and I wanted more power than the standard 120 volt/30 amp/3600 watt service. I also wanted the Inverter to power all the AC Loads, and while they make 120/240 volt inverters, they are not practical to use in a camper.

4. Why Victron Equipment? To start with, Victron Energy is a long-established, international company with a reputation for manufacturing quality products. Especially in the mobile sector. But the main reason I went with their equipment is the integration of all their components with a central setup, control, and monitoring computer (CCGX or Venus GX). Theirs is the first system I have seen where the battery BMS directly controls the charging Voltage and Amperage being sent from both the inverter/charger and the solar charge controller. They call it DVCC (Distributed Voltage and Current Control). It’s quite a concept, the battery system controls its own charging rather than relying on setups in external charging devices.

Conclusion

Well, that about does it for this first article. I look forward to getting your feedback, both positive and especially negative. You can’t learn anything if all people say are good things about a design. My batteries don’t get here until early August, so I’m going to start on the technical article and hopefully get it finished in late July. (Ed. note: part 2 of this article can be found by clicking here).

I have included some “teaser” photographs of the project’s progress to date.

The DC Load Center wiring
The AC and DC Panels and the Color Control GX are installed in the door of the enclosure.
Backside of the door
Inside of the enclosure. The big blank space in the back is for the Inverter/Charger. The wiring is a work in progress.
The Terminal Block and Bus Connections are on the left side, I will soon be adding the “Pass Through” connectors.
Nothing done to the Battery Box yet. The Victron BMS is not mounted, it’s just laying there.

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About Pat Davitt 2 Articles
Pat Davitt is a former Naval Aviator who served on active duty for eight years and retired from the Naval reserves after 20. He worked as a senior project manager for a general contractor and later researched, installed, and setup computer systems for construction companies. Today, Pat lives on a small ranch in the Davis Mountains of West Texas with his favorite horse “Rocky” and dog “Zorro”. Even though he already lives in the “boondocks,” he wants to visit other remote areas in the United States, which led to his search for a truck camper.

6 Comments

  1. Thanks to all for this technically well written article. Please provide a full schematic drawing of the entire system. It will help in understanding the flow from the primary feeds, solar/shore, to the batteries and loads. There is much going on with your design/system that we want to understand better. Yall’s efforts are much appreciated. The wife and I play with surplus IRIS/SPACES equipment, to power small loads when boondocking.

    • Bill,
      Be careful what you wish for. Part two of the article will be coming out in the not too distant future. I think it will satisfy your wish for details. 🙂

      Pat

  2. I’m working on my own system right now;
    35 – Nissan leaf batteries backs configured in 7S20P (24V system) with 13.5kwh usable (batteries are carried in a 2″ high platform between the truck bed and camper).
    Samlex EVO-4024 Inverter (4kw/24V) with 105A charger
    Electrodacus SBMS Solar charge controller/BMS
    8-205W mono solar panels in 4 stacked racks with bottom panel extending 32″
    105A/24V second vehicle alternator to charge while driving…….installing it in a Lance 1130 camper on a F350….It will be overweight but this is just a test bed which will be transferred onto a 20′ expedition vehicle on a former Steward and Stevenson 5 ton truck.

    • Steve,

      You’ve hit on what the ultimate camper battery’s’ physical dimensions should be; thin and flat. I tried to find commercially available flat batteries that would be compatible with my centrally controlled system, but could not. Hopefully, some one will produce them, for market, in the future.

      Thanks for your comment.

      Pat

    • Patrick,

      Thanks for your comment. My Marine Drill Instructor “Gunny Bodine” at Aviation Officer Candidate School, thought me many things; including “Attention to Detail” that have served me well throughout my life. Only guy I have ever met that could make a complete sentence out of nothing but cuss words.

      Pat

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