Wiring From Scratch Avion Ultra C11 Truck Camper
I am a firm believer in not allowing the perfect to be the enemy of the good. While having a completely renovated camper is preferable, we don’t want to spend years in one place, building a dream camper when we could take the process in stages and travel as we work. We are prioritizing replacing rotten flooring, old wiring, and insulation so that we can reinstall the inner walls and travel as we complete the rest of the camper. Even in its gutted state, this camper is better than the shell we were living in before.
A Little Background
After stripping out the interior of our 1970 Avion Ultra Truck Camper, it is time to rewire the beauty. I took a few hardware classes in grad school so I have a small scale understanding of circuitry, but this is a first for me. I have read a fair bit on upgrading or patching RV electrical systems. But I have yet to come across anything comprehensive regarding a full, top to bottom rewiring project. So, that is why I am writing this post: this is my proposal. I hope that, in listing my hypothesis, others—far more knowledgeable than I—can point out my mistakes, misconceptions, and direct me to better resources, products, or just offer some advice.
Where Does Power Come From?
As many overviews of camper wiring will observe, there are five major potential power points to consider when wiring the camper:
- Shore Power – from some 50-AMP or 30-AMP hookup
- Truck Alternator
- Solar Panels
- Mobile Generator
At the moment, I’m concerned with setting up a system that supports shore, truck, and battery power but will be wired to support solar and maybe a generator in the future.
I haven’t settled on the refrigerator or heater, but I assume that they have sufficiently similar specs that I can go ahead and wire up the outlet for now. In the future, I can just hook into those wires with the appliance.
My Shopping List
After a fair bit of research, I understand my shopping list covers:
- Power Sources
- Surge protector
- Fuse Box (or not?)
- 120VAC to 12VDC three-stage converter
- Battery Monitor / Recording Meter
- DC to AD Inverter
- tons of wiring
I already have the basics: wire cutter / stripper, multimeter, etc.
110-Volt 50-AMP Shore Power Inlet
My understanding is that shore power comes either in 50 AMP or 30 AMP hookups but that it is easier (and safer) to step down from 50 to 30 than to step up from 30 to 50. But, it seems that the occasions when one would have to step up to 50-AMPs is rather rare and building for 30-AMPs is less
At the moment, the inlet for shore power is a cable hardwired into the camper. The cable is held in the drivers-side lower rear portion of the camper, near the bumper. This is very far from where the batteries would logically be stored. It appears that the location was chosen so that the breaker box would be in the closet. But. given that I intend to rearrange the floor plan of the camper, is there a major reason to keep the inlet in the far back corner?
I will be replacing this single, hardwired cable with an inlet plug. This will free up the location of the inlet, as the cable to connect to shore power can be stored most anywhere. As such, I am considering moving the inlet further forward, to line up with where the batteries will be stored.
The truck alternator is our most constant and reliable source of charge. We can be in the middle of nowhere and still charge our batteries so long as there is gas in the engine. This hookup is not only a source of power, but the means by which the the break lights and blinkers on the camper are controlled by the truck (the Avion camper covers up the truck’s lights). As important as it is, it appears that this is one of the most simple components as the seven pin hookup is industry standard, often referred to as the umbilical or “pigtail. As such, I’m planning to just get a basic plug such as this one.
I’m right in the middle of removing the old Avion Ultra fuse box. It has clearly seen better days. Moreover, since those days, circuit overload protection has changed. From products I see online, I can buy a breaker system (breakers serve the same purpose as fuses but simply flip themselves off when overloaded, thereby not requiring replacing every time someone thinks they can be clever with a blow dryer) built into a converter. As such, I would assume that this would be preferable…
120-Volt AC to 12-Volt DC Three-Stage Converter
This converter takes shore power—which should be 110 volt AC, more about that when discussing the surge protector—and converts it to 12 volt DC, which charges the batteries and powers most camper appliances. In reading this blog post, It seems that I can choose between 45-, 60-, and 80-amp models. These amp values are dependent on what I’m planning to charge. The more batteries (and high amp) in play, the longer it takes a low amp converter to charge the batteries. From this post on RV.net, I get the impression I may be swaying to a 60-amp converter. But I need to settle on my batteries first.
I see that certain solutions, like the Parallax Power 5300 Series 50 Amp Service Power Centers combines the converter with a breaker system, thereby also solving my question of what fuse box to buy…I think?
Why Three Stages
Apparently, a lot of factory truck campers only have a single stage converter (at least, as of 2004 when this forum post was written). This is a problem, as the batteries we will use have three stages to reach full charge. So, these converts don’t make optimal use of the battery. Instead, we should have a three-stage converter to support the needs of the battery.
I have only occasionally seen reference to the importance of positioning certain components relative to each other. However, as far as I’ve read, it is critical to have the charger as close to the batteries as possible. When charging the batteries, it is critical to apply voltage at certain levels relative to the battery’s state. Resistance in the wires can result in voltage loss, and the longer the wires, the more that is lost. That can result in a significant inconsistency between what the charger anticipates and what the battery really needs. So, minimizing that distance minimizes the threshold for error.
Currently I’m leaning towards a Progressive Dynamics converter. Not only was it the brand that supplied the converters original to the Avion, but they continue to have a good reputation among RVers. The PD4060 60 Amp Inteli-Power Mighty Mini Power Center appears compact and should power the two 12-volt batteries that I am leaning toward.
Here’s a biggy. Not all campers come with a surge protector built in. Yet, from what I have read in some forums, older RV parks can have very unreliable voltage from their hookups. As we intend to boondock and then duck into civilization every once and a while, we want to be able to take our charge where we can get it…safely. Thus, we want to introduce a surge protector to protect our camper and our computers! I’m a little confused, though, when shopping around, as they seem to just be extensions for the hook up wire such as this listing. I can’t seem to find something for hardwiring into the camper. Perhaps this is something that can come as part of a Power Center (combining the converter and breaker box)?
There are a lot of types of batteries and battery arrangements. Since we have completely stripped our truck camper, limitations like the battery box size are not an issue. Instead, what matters to us is creating a system that allows us to spend days off the grid, boondocking. So having the right battery situation is critical. As our main use case would be charging two computers, running lights, and a few fans. We intend to be powering the refrigerator and stove on propane (while the truck is not in motion). I don’t think amperage is our main limitation, it’s amp-hours. Our goal is to allow the optimal amount of battery use for boondocking situations while taking cost and space into consideration.
When powering RVs, there are three main battery type contenders: wet cell, gel cell, and AGM batteries.
Wet Cell Batteries
Wet cell batteries are cheaper but dangerous because they off-gas hydrogen which can be explosive in enclosed areas. So, to use these batteries, you must store them somewhere that vents out of the camper. (AGM batteries also off-gas but at much lower rates.) In addition, as the name would suggest, wet cell batteries need to stay wet, which requires regular maintenance checks to keep the water level balanced.
Gel Cell Batteries
Gell cell Batteries are considered the “no maintenance” equivalent of the wet cell batteries. While they do not require the same maintenance as wet cells, that is a compromise made on life span. A well maintained wet cell battery will have a longer lifespan than its gel equivalent. To top it off, gel cells also off-gas and require ventilation.
Absorbent Glass Mat (AGM) Batteries
Instead, we’re willing to spend the extra cash for the AGM batteries. AGMs pretty much do not offgas and do not require the maintenance of the wet cell batteries. They also charge faster than the wet and gel cell batteries. This has to do with their lower resistance levels, so less energy is converted to heat. Many testimonials also note that AGMs have longer lifespans, though, whether this is a matter of the battery or poor maintenance on previous non-AGM batteries is anyones guess. The down side? they are much more expensive.
Since we aren’t using them to start a truck or such, the type of AGM battery we want is true deep cycle batteries to withstand repetitive discharges up to 80 percent or more numerous times, and still provide amperage at their rated capacity according to this blog post. Wet and Gell cell batteries also can be true deep cycle. The challenge is to make sure, when selecting any of these varieties, that the battery is true deep cycle and not just the marine deep cycle, which isn’t as rugged.
|Battery Size||Amp hours||Voltage|
|Group-24||70-85 amp hours||12 volts|
|Group-27||85-105 amp hours||12 volts|
|Group-31||95-125 amp hours||12 volts|
|4-D||180-215 amp hours||12 volts|
|8-D||225-255 amp hours||12 volts|
|Golf Cart||180 to 225 amp hours||6 volts|
|L-16, L16HC etc.||340 to 415 amp hours||6 volts|
From multiple forums and blog posts I’ve read, it is best to have two batteries—either two 6-volt golf cart batteries wired in series or two 12-volt batteries wired in parallel. Why two 6-volt batteries are better than one 12-volt battery appears to be because the two 6-volt batteries in combination can put out more amperage for the 12 volts than a single 12-volt battery. By that logic, it would be better to buy four 6-volt batteries, wire each pair in series and then connect those in parallel rather than just wire two 12-volt batteries in parallel.
Though, I have also read that lead acid batteries do not play well in parallel. While, conceptually, two brand new batteries of the same make and model when wired in parallel should operate in perfect concert, in practical use, one will tend to drain and charge not in perfect sync with the other and lower overall performance. That being said, I’ve only read that once.
HOWEVER, the problem with two 6V in parallel is that, if one battery goes, you are sunk. Two 12V batteries mean either could still function, just at a lower amperage. Given our boondocking intent, this is a major consideration. Instead, I’ve come across 12V parallel circuits where the batteries are connected with an A, B, A+B switch so that power can be easily accessed by any configuration of batteries.
Cautionary Notes on Battery Maintenance
- “When replacing your batteries, remove the negative cable first because this will minimize the possibility of shorting the battery when you remove the other cable…then reconnect the cables in reverse order,” From The 12 Volt Side of Life
- “Thinly coat the terminals and terminal clamps with a high temperature grease or petroleum jelly (Vaseline) to prevent corrosion.” From The 12 Volt Side of Life
In the meantime…
At the moment, I’m considering starting with a single 12V battery. The truth is, we are taking this build in stages. Early on, we don’t need the amperage of two 12-V in parallel. Therefore, we’re going to buy one 12V AGM battery as it is less expensive but still does not off-gas. A cheaper battery (probably from Sears) with a shorter lifespan is acceptable given it is a stopgap. Also, several RVer’s have noted that their first battery tends to have a shorter life as they learn how to properly handle it. This also gives us more opportunity to determine our long term load as we gradually add new items to the circuit. I read something in passing that the Cabella’s batteries are made by Trojan. That warrants further research.
We fully intend to add solar panels to our rig. Given our desire to boondock, these seem a logical extra source of power. That said, they can be an expensive investment, so, right now, I just want to wire the rig in preparation for adding solar panels. So far as I’m aware, this just involved laying the wires for the solar panels…?
Solar Panel Tilt Mount Kit
One thing we are considering biting the bullet for is going ahead and mounting the solar panel mount. Our thought is that, since we have the interior walls completely stripped right now, this could be the best opportunity to mount external equipment. This can improve our mounting options as well as sealing any holes to minimize leaks. It does seem like the mounts we’ve seen are often designed for a particular solar panel, such as these. But there are some tilt mounts that appear to be more flexible. So, we would probably go with those…
Battery Monitor / Recording Meter
Yet, from further research, it appears that battery monitors are of limited use. They tend to be optimisitc when reporting battery charge. But a particularly handy tool is the recording meter, which reports on battery consumption over time. This is a great early addition to a circuit to monitor our usage and get a sense of what we need before we invest in a solar array.
DC to AD Inverter
After my research on Charging A Laptop On 12 Volts, it’s become clear that an inverter to supply 120VAC from 12VDC is important, even when Boondocking and striving to optimize power consumption. Handy Bob Solar swears by Magnum inverters. That being said, I’ve just begun to dip my toe into this matter.
Something I don’t hear a lot about in wiring discussions is the wires. I guess this is because it’s pretty obvious for those in the know. As someone not in the know, selecting what gauge of wires to use on the camper involves a little guessing. Gauge is important because, the larger the wire is, the lower the resistance. The lower the gauge number, the larger the wire diameter is. According to Handy Bob Solar, RV wiring is a special consideration: “It is good practice to use one or even two sizes bigger wire than recommended to limit voltage drop.”
I did find reference to wiring gauges in this article with a passing reference to Northwood campers using 14 gauge wiring with the exception of the charge and ground wires where they use 10 gauge wire for better conductivity. (The wire gauge and diameter are inversely related: the higher gauge the wire, the thinner it is.) On the opposite extreme, this article about optimizing your alternator charging arrangement relies on massive, 2-gauge wires from the alternator and 4 guage within the camper because “that side of the connector will only accept 4 gauge maximum.” Even so, that’s some big wires. According to bigfootford on RV.net, “High strand count solar/welding wire is what you need.”
Moreover, when determining the wire gauge to the converter, consider the distance x2 (for back and forth) and the amperage needed, “The biggest of the two (charger current or load current) will determine how big your wire should be.” Also notes “You should fuse your battery wire for a Catastrophy. Go to a auto stereo shop that does installs. They will have fuses that are great.” I assume that the fuse / breaker box with the converter should handle that requirement unless it is important to fuse each battery individually.
Thus far, I have only gotten my hands on one diagram, but a few considerations regarding wiring procedure have popped up:
- “neutral and ground are NOT bonded in the main power distribution box as they are in a house” from forum post
My Ask From You
I know, it’s a lot. The challenge, as I see it, is to pick the right products that go together. This is a systems approach. Rather than finding the best battery or converter or inlet, I want to find the battery, converter, and inlet that best work together. If I said something stupid: please correct me. If I missed an important point: please direct me. I would be so grateful for any product recommendations, links to any tutorials on truck camper / RV wiring, or general input.
* The alternative is two 6 volt batteries in parallel, but we want to boondocking, so more seems better. Right?