by Dave Boyer

I went over the air conditioner system and covered some issues with AC (alternating current) power in the previous posting (part 9). This section will go into more detail about RV electrical systems and components. From the beginning I want to make note that there are several equipment options available out there other than what SMB offers.

Just be aware that asking for a specialty item to be installed might make you the beta tester for that item.

Electrical and Electronics:

The electrical system is heart of my vehicle. It’s composed of both an AC and DC section. The majority of vans coming off the line (including my own) have two DC systems that serve separate functions, one as the engine starting system and the other as a secondary 12 volt power supply. The secondary battery system is what supplies DC to the cab while you’re camping and is referred to as the house battery. Both starting and house systems can contain one or more batteries each. Standard builds frequently include wiring circuits for the AC and DC outlets that are located throughout the van. The AC section of the vehicle usually incorporates an inverter and typically controls battery charging as well as supplying alternating current to devices such as a microwave. The inverter primarily runs off the house battery but is frequently tied to the engine system to aid with heavy load demands (such as the microwave) that may be used. When running the motor at high idle the alternator will help offset energy being pulled out of the house battery. When using light loads or less, the alternator will charge the house battery. For boon docking purposes, the house battery is a crucial element of the vehicle and needs to be kept as fully charged as possible. If solar panels are installed, they normally will keep the batteries topped off without the need to plug into an alternate power source. With enough solar the refrigerator can run off the solar system by itself during good sunlight and still supply a reasonable charge to the house battery. This is very important and should apply while sitting in the driveway or out in the sticks. It’s a good idea to correctly size the solar and battery components together to achieve maximum efficiency. Large alternator systems that are able to supply higher than average output are also worth looking into.

A self sufficient DC power system has some big advantages. Having a pre stocked refrigerator is sure nice. I’ve said it before; the time it takes to hit the store and load up wastes valuable time. Besides, after a rough day at work it was the last thing I wanted to do. Often this would persuade me to postpone the adventure or eliminate it all together. Being able to jump in my van and leave for the hills without the hassle of loading up the refrigerator and a bunch of equipment at the last minute is a definite plus. I usually spend a great deal of time running to the store buying supplies in preparation for most excursions. During the cooler months when the refrigerator does not cycle much, I leave it stocked with standard condiments and the more non-perishable foods. In the hotter seasons I fire up the refrigerator a few days before I leave. A day or so before I actually leave I swing by the super market and load up the refrigerator on the spot. The next day or whenever I’m ready I can leave on a moments notice. This is a true time saver.

Sportsmobile’s standard electrical design worked well for me but eventually I made some changes.

Picking the correct power system is unique to the owner as well as the type of RV. I’m going to go over a setup suited for a trail rated Sportsmobile 4×4 as I see it. The way SMB builds the electrical system is fairly straight forward and they usually start with a basic approach, so design changes are up to the customer. The upgrades I added after taking possession of my van were due to my experiences in the field. I’m sure some will disagree with my opinions.

My personal view is that Absorbed Glass Mat batteries are better suited for the off road conditions a Sportsmobile might encounter. Conversely two wheel drive RV’s might be better suited for deep cycle wet cell batteries. I’ll briefly touch on this issue but more can be researched in the links provided throughout the article. Although most web site editorials concerning battery systems provided here cover typical RV’s, these articles are a good source of technical information. Advances in industries such as the solar market make these commentaries slightly out dated but still worth a look.

Many RV electrical systems (including mine) revolve around: A 110 volt system which supplies standard household voltage to operate AC equipment and outlets located throughout the vehicle when plugged into a power source.

1) The starting battery or batteries.

2) The vehicles alternator charging system.

3) An isolating system. A method to keep the starting and house batteries separated from each other.

4) A deep cycle battery system. This can be one or more batteries that provide 12 volt power to DC equipment and power ports.

5) A solar array, which maintains the battery bank charge level.

6) A power inverter, which supplies AC power while camping in remote areas. Inverters change direct current voltage to household alternating current. In this case 12v DC to 110v AC. Most inverters double as the shore power battery charger when connected to an AC power system. Standalone battery chargers and DC power supplies are available but these also usually require AC shore power to operate. DC power supplies are sometimes called converters and perform the opposite function of an inverter. They change 110v AC to 12v DC. Many also double as a battery charger.

The AC system:

Many recreational vehicle owners live with the idea of obtaining the necessary household AC voltage where they camp. Larger RV’s have appliances that require 110 AC so many campgrounds have power pedestals available that the RVer can plug into. This is referred to as shore or pedestal power. Most SMB designs incorporate an AC system that allows the owner to use an available power source. I have yet to use shore power at a campground but I do plug into a power pedestal at home to charge batteries and use certain items like ventilation fans during summer and devices in winter to dehumidify the interior when necessary. Although finding an AC power source in the backcountry where I planned to venture is usually out of the question, I find it useful around civilization and at home. Running the Starcool add on air is nice when visiting areas where it bakes in the warmer seasons and also helps keeps van cool at home before I depart during those dog days of summer. This requires a 30- 50 amp power supply to furnish the vans AC system and air conditioner with the correct voltage. These power centers along with the correctly rated extension cord must supply around 118 to 124 volts to prevent damage to the air conditioner. This image show a typical shore power pedestal. I just recently installed this at my residence.


Note: take caution when connecting the main power plug to any kind of shore power. Make sure that the power source is dead before plugging into the van. Without turning off the source I have found that the power plug arcs even with most of the equipment is off in the van. This can eventually cause problems at the outside plug. It is also important to check the voltage after connection to any unfamiliar power source. (See part 9).

The vehicle starting battery:

This is the stock battery that comes with the vehicle which is also referred to as the chassis system. Diesel motors usually have twin batteries for starting the engine while gasoline rigs generally have only one. Whether the vehicle has one or two, leaving the headlights on can lead to the same result; looking for someone to jumpstart your vehicle. Having twin starting batteries is an advantage if the rig has devices that pull heavy loads such as an air compressor or winch. The only problem with duel batteries will be discussed below in the DC section but it’s safe to say two is better than one.


Many ambulance vehicles use twin alternators to supply enough power to run the necessary equipment on board along with keeping the charge rate up. Most have an extra air conditioning system which really put stress on the charging system. Space is tight under the hood so my thought is that SMB orders vans with single alternators for this reason. But I found that the single Ford alternator was reducing charging times to a point that running the add-on air conditioner was causing a slow re-charge rate. On top of that there were times that the load was so great it was actually pulling a few amps off the batteries. This was not a problem most of time and hinged on what else was running other than the air conditioner. Between operating a bunch of extra apparatus as well as the standard vehicle equipment, kicking on the air started to kill the batteries at a very slow pace. A long drive with a bunch of stuff on could take a toll. This is a flaw on SMB’s part IMO but many owners do not want or need an extra air conditioner. To remedy my low amperage problem, I ordered a 200 amp alternator and had it installed. Now I can run everything needed and still have the ability to stay in the positive charge zone. As with any aftermarket device, there is a chance that the quality is substandard to OME. Well at least that’s how Ford sees it, so the warrantee is also affected. The new 200 amp alternator works well for me but I would rather have the twin alternators offered by Ford. Like I said, it’s possible that some owners will not need all this extra amperage so your mileage might vary.

Battery separation:

Being most Sportsmobile’s have two battery systems, some method to keep the two separate while the engines off is a good idea. Although it’s possible to tie all the batteries together, if something is left on for an extended length of time there’s a possibility of killing all the batteries on board. Even if you still have some power it might not be enough to start the vehicle leaving you stranded. But the alternator must charge all the batteries while the van is running so they must be wired or bused together. There are a few ways to separate the bus work. One is a high amp switch that the owner must operate manually. While the engine is running, the switch is set to connect the batteries together. This ties the house system to the starting batteries so alternator can charge all the batteries. Unfortunately if you fail to separate the two when the engine isn’t running and something goes wrong you have the possibility of killing the both battery systems.

Another way to keep batteries separated is an isolator circuit. These allow charging in a single direction via an electronic circuit device. SMB used isolators for a number of years. They’re designed to keep a charge flowing into the house battery setup when the engine is running. Turn off the motor and the starting battery is isolated from the house system.

A third type is a separator relay. These use a solenoid to make a physical gap between relay points. Usually an electronic circuit samples the voltage which opens and closes the relay at a specific voltage. SMB used a company called Sure Power for the separator in my 2006 van. I have had problems with the relay but most of the trouble was due to other reasons, not the separator itself. I still would like to have a backup circuit in case of failure in the backcountry. I plan to add a secondary device that will bypass the primary relay if needed. Having a backup can be useful if you’re miles from a repair shop. Running out of power can really ruin a trip, so it’s best to be equipped to handle any situation within reason.

There are several other companies such as Blue Sea that make these products and I’ve shown the links to Sure Power because that’s the product used by SMB during my vans construction.

Batteries and the DC system:

I’m going to delve into this section with more detail because problems with the DC system can be irritating. Electrical trouble can be confusing and may end up as a major headache when things go wrong. One problem that many owners experience is having a system that’s inadequate to handle the specific load. The end result from choosing an incorrect system can be flat out expensive due to battery replacement or costly upgrades. Other electrical problems that occur can be caused by lack of maintenance, operator error, equipment failure, or manufacture defects. Something as simple as accidentally leaving a small light on while the vans sits idle can be a costly mistake. So far I have been lucky but I know others who haven’t. Electrical problems can be tough to troubleshoot and I’ve had a couple that cost me some bucks but nothing bad to date. It helps to understand how things work. This is especially important if field repairs are necessary. It gives you a chance to troubleshoot the problem and get yourself out of a jam. Besides nobody likes to be bit in the ass for repairs do they?

There are several factors to take into consideration when choosing the correct battery system that suit your needs. It’s up to the user to determine the amount of storage capability and what’s considered necessary to run the 12v DC system plus any additional equipment for a given length of time. The battery, no matter what type or rating it has will be affected by these factors below:

1. Maintenance. This includes access to the batteries. For the most part maintenance is the number one factor why batteries fail in RV applications. Maintenance is more or less an umbrella aspect when dealing with batteries. Watching voltages, charging times, and even temperature are just a few variables that come into play in maintaining a battery. Keeping electrolyte levels up on wet cell batteries is critical and needs to be check frequently. Terminals must be kept clean from corrosion and have solid connections. The complete wiring harness must be free from sharp contact against chassis parts which might compromise the insulation and cause a short.

2. Charging and discharging specifications. Storage capability (how much power it will hold) will affect charge and discharge times. Each design or type can vary from one to another. The depth of discharge can also vary between battery manufactures as well.

3. Durability and weather exposure. This controls life expectancy. There are several factors to deal with here.

4. Price. This speaks for itself. Just remember you usually get what you pay for.

5. Mounting procedures. Weight, physical size and positioning factor in here.

6. Safety. The major concern is off gassing under charge but corrosive discharge and physical damage come into play also.

I requested the installation of a standard Lifeline deep cycle 4-D deep cycle AGM house battery on my original purchase order.

The house battery supplies power to the interior lights, water pumps, refrigerator, and other 12 volt DC items such as fans and igniters used in heating devices. Most vans have several 12 volt power ports located throughout the interior. Anything that uses common household power is fed from the DC to AC inverter (provided one is installed) unless the van is connected to external AC power via a properly rated extension cord. If an inverter is part of the install, it also runs directly off the DC battery system unless you’re on shore power. Many inverters act as the high end battery charger but usually let the AC plugs work directly off the external AC power source when plugged into a power pedestal when there is no need to run the inverter.

The 4-D AGM battery I requested was rated at 210 amp hours and still is the setup used by a large majority of SMB owners. (Note: this spec was in 2005 and may be subject to change). But it is also your prerogative to use batteries of your own choice or eliminate them completely. Everything inside the vehicle can operate off the chassis batteries but having an isolated house battery system helps to eliminate any chance of waking up to dead starting batteries. Having to look for a jump start is something that’s best avoided in the back country. Generally I could use a florescent light or two for a couple of hours plus run the refrigerator and heater all night utilizing a single 4-D battery. During the evening hours in extremely cold weather, I usually run the water heater for a brief period to keep the heat exchanger from freezing and warming the engine block. Warming the engine block before dawn helps with cold engine starts. By morning the battery would be low but not dead by any means. Eventually I made the decision to add a second 4-D battery which became one of the better upgrades made to my van.

Understanding how long an electrical device can operate directly off the DC system is very important. Knowing how much energy or “fuel” the house system is able to supply and for what length of time is beneficial. This has nothing to do with the vehicle starting battery(s) as a rule unless:

1. There is no house battery system wherein the starting battery(s) double(s) as the house DC source.

2. The house battery system is hard wired directly to the starting system without any type of isolator, separator, or battery switch.

3. There is a malfunction or operator error with any of the above including the house battery system itself.

Here is a very basic way to look at batteries.

It’s easy to think of a battery system as a bank account. You start off with a specific amount in your account which is represented by a fully charged battery or set of house batteries. Every battery or group of batteries can only hold what they have been designed to hold, so the account has a maximum upper limit generally expressed in Amp Hours or AH. For the sake of ease, Amp Hours also act as money. The more AH your batteries hold the bigger the account will be. In fact a group of batteries is referred to as a “bank”. Three 120 amp hours batteries equal a battery bank rated at 360 AH. Two 210 AH batteries equal 420 AH and so on. Every time you use an electrical device it pulls a few bucks out of this account or “bank”. Higher wattage items, (devices that pull more amps), steadily pull more money (amp hours) out than the lower wattage types. Using the microwave or an electric heater strictly off the house battery system for long periods of time will drain your account very fast, often leaving you broke before the night is over. Once the account is drawn down you’ll have to make a deposit. The only way to fill it is to replenish the banks maximum amp hour rating which is done via shore power AC (usually the inverter set to charge mode), running your engine, or solar. The big money coming in is represented by the AC charger while at the other end is solar (if you have it) which is usually a smaller pay check. But something coming in is definitely better than nothing and the larger the solar system is the better. The engines alternator is constantly putting in a few bucks as long the engine is running at a reasonable RPM and will bring your account back up within several hours of driving most of the time. All recharge times depend on how much you actually take out plus how fast the charging systems can bring the battery or bank back up to full. Obviously anything using the 12 volt system during the charge will also affect how long the recharging takes.

I will go over the connection between the starting battery system and the house system later. For now just look at the house system as a completely isolated 12 volt DC power source. The links in the latter portion of this article show how to actually do the math, plus there is a bunch of technical gobbledygook on how batteries charge and discharge. A few other factors such as temperature can make a huge difference on how much power a battery can hold. Even with all the technical data available, judging how much DC reserve that you need can become a guessing game. Finding items that run off DC rather than AC can help reduce losses because the inverter itself pulls a few amps just to operate. Many large truck stops sell DC items that normally run off AC current. There are several on-line stores that furnish special DC products.

Just because something operates off 12 volts doesn’t mean it will be more efficient, only that the inverter will not have to be used. For example, a small household fan may pull 3 or 4 amps but by the time you factor in the power that is needed to run the inverter, total amps being used might be as high as 7 or 8 amps. On the other hand you can purchase a 12vDC fan that pulls a total of 3 amps running on high. The main problem with 12 appliances is how well they actually work compared to their AC counterparts. Most AC products seem to be better built and there isn’t much to choose from in the DC world. I have yet to see a 12 volt George Foreman Grill, an appliance that some SMBers use. So there are times to fire up the inverter, plug in something and watch the amps being sucked out of your battery. Something that pulls heavy amounts of power such as household grills, crock pots, toasters, and hair driers can reduce the batteries charge state quickly and must be used sparingly. Even two large house batteries do not supply enough total amp hours to operate the big power hogs (air conditioners, microwaves, electric heaters…etc) for long periods of time. Running the engine will only supplement what’s being pulled out of the bank by these type items. Shore power or a properly sized generator is your best bet for running these devices. You might ask “what about solar”? The advantage of solar is when you have a big enough array to off set something that pulls a light load and runs continuously such as a refrigerator (more on solar later). Yet a reasonable sized battery bank makes common sense. Depending on the layout of the vehicle and model, mounting space for an extra battery is something best thought out during the initial order. I just got lucky that I had enough space to jam one more in. If you might plan on a 2nd house battery down the road, take care of it during the build.

Some of these batteries are very heavy and can add substantial weight to the overall GRVW. If installed toward the back axle, it can add to a rear sagging problem, something that has plagued some of the older Sportsmobile’s in the past. In 2008 Ford made design changes in the Econoline series and SMB upgraded the spring pack which has eliminated some of the sagging problem. The 2nd battery makes it able to run some extra equipment that I found was not possible utilizing a single 4-D battery. No matter what size battery or group of batteries that’s on board, you should know how much power you’re starting with, how much is being used, and how far you can take them down before things need to be shut down. Someway to keep an eye on the 12 volt system becomes somewhat crucial. The solution is adding monitor to keep tabs on the batteries status. Since I upgraded my battery bank to 420 amp hours by adding a second battery, I can run my microwave for limited periods of time on low power provided I monitor how much I am pulling out. There are several monitors on the market to choose from and some are nothing more than cheap digital voltmeters. It’s a fact that a standard voltmeter can be used to determine a batteries level but more sophisticated gauges such as those made by Xantrex will give you a better overall picture of your batteries health. I purchased a monitor called a Link-10. It works well to keep me up to date on the status of my house battery system and also helps in troubleshooting DC problems if they occur. This is a “must” item to have IMO. The link-10 has been replaced by newer models.

But back to the batteries; maybe you don’t need all that reserve. I operated with a single battery for two years and never ended up below 11.8 volts although I was surprised how much the lighting inside the van pulled down the system. What might work well for some owners is installing a larger single battery such as an 8-D. One might think that an 8-D has the same amp hour rating as twin 4-D’s. Unfortunately this is not the case but it does have a higher AH rating than a single 4-D.

The working life span is usually about 5 years (or longer) with correct charging and discharging procedures, but at around 400 bucks for a 4-D battery, it’s something to consider as a long term maintenance cost. Here is a link that has information about battery charging and other statistics.

I am no expert in this field but I have dealt with deep cycle batteries on bass boats since 1980. I prefer absorbed glass mat (AGM) batteries for a variety of reasons and gladly made the switch when they were introduced on the market. I tried gel batteries in the early 90’s for easier maintenance but switched back to wet cell lead acid deep cycle marine batteries due to performance issues. I was very happy with my first set of AGM batteries compare to gel batteries. Gel types can’t take fast high charge currents and their life span was short. Both batteries do not require monitoring electrolyte levels making for easy maintenance but the gel battery had charging disadvantages. I do know glass mat batteries can sit at full charge for longer periods of time when not in use, and charge faster than wet cell batteries. This is convenient for systems that use an alternator which sporadically charges the battery. Even though most all batteries can only be recharged so many times during its life, AGM’s don’t like being dropped below about 50%. The idea is to have a big enough battery system so you have at least 50% of the power left before the charging session starts all over. Wet cells can go down to about 20% before having to recharge but dealing with fluid levels is a PITA. How many times you discharge the battery and how far it’s taken down (the depth of discharge) varies slightly depending on the type of battery. This is referred to as cycling, or charge-discharge cycles. Each battery design has a specific point or charge level where the battery should be re-charged to extend its life. The depth of discharge of my old wet cells was actually better than the AGM’s when the batteries were dropped to a low state but I usually never took my batteries below 40% and the AGM’s charged so fast it was a good switch for me to make. Most every time I lost a wet cell battery had to do with exposing the plates during a charge or evaporation when the battery sat in a hot garage. So for me the AGM’s lasted longer. Of course the quality of the battery can effect cycling, so going with a company that has a good reputation of building a premium product is worth looking into. All these factors make AGM batteries a good choice for operating with solar systems that supply a continuous light charge on a daily basis. Of course any battery can fail if overcharged or damaged, but AGM batteries resist freezing, leaking and won’t off gas as a rule. Glass mat batteries are built tough. They can take more abuse than other batteries which make them ideal for off road use. Another big advantage of AGM’s (and gel types) is most can be set in any position even upside down. This can be helpful while mounting in tight spaces. Although I personally would not install a battery inside living quarters, just the fact that they are sealed makes for a safer install.

On the flip side AGM’s are generally more expensive than standard deep cycle wet cell batteries plus they seem heavier. But the biggest disadvantage to AGM batteries is when they are subjected to low levels of discharge and especially if they sit at that level for a lengthy period of time. I strongly suggest reading up on depth of discharge from the link below. It will directly affect the lifespan of any battery. Taking a battery down to 20% probably will generally not cause permanent damage if it’s not subjected to this frequently but there are limits on how low and how often. Most all batteries should sit at the Float charge state when idle which is around 13.2 volts. Each style of battery reacts differently to discharging but all of them benefit with light maintenance charging to achieve their float level. Lead acid batteries that I’ve let drop to low voltages have bounced back better than the AGM’s I have mistreated but I’m more careful now and keep my batteries at their full level as much as possible especially when sitting idle. OK the disclaimer: The information provided is only my experience in dealing with deep cycle batteries and might be speculation on my part. I have no scientific data to back up my findings. It’s up to the reader to verify this information. Here is one of the best links on batteries I’ve seen.

So how can you keep from destroying your battery investment that you’ve decided to go with? Watch the battery monitor and don’t let the storage capability fall below what the manufacture recommends. Loosing 1000 bucks in batteries, not to mention the hassle of replacement is not good on the pocket book. As I stated earlier, another option is to look into is running a larger single battery. There are definite advantages to running a single battery. One of the big problems with running a bank of batteries (2 or more) is if one fails. A faulty battery in a bank can act as a teeter-totter. In other words, an old battery in poor shape can pull a brand new one down. When parallel connecting a group of batteries they should be similar to each other. It’s important to use all the same rated batteries when busing a bank. In fact it’s a good idea to use the same manufacture and even the same age batteries. Make sure you don’t get one that’s been sitting on a shelf for a couple of years in a warehouse. A batteries property can change with age and might even degrade while sitting on a shelf. The only true way to test the discharge rate is with a carbon pile load tester or similar. As I said, a battery that has a reduced storage capability tends to pull the other(s) down when parallel connected. So when one battery malfunctions, it’s a good idea to swap the other(s) out after it’s determined what caused the failure. Yea, big bucks if one fails. There are exceptions to this, but if the batteries are of equal age, chances are there will soon be a similar failure with the older battery. Now if a battery bank is a year old and you loose one all of a sudden due to no apparent reason you’ll probably be OK to just replace the bad battery if no damage occurred to the other batteries. Most information shows that permanent damage can occur to an AGM battery if the voltage of the battery drops below 12 volts on a regular basis. Not that it will ruin the battery immediately, rather it will eventually lower the AH rating and what it can store will slowly be reduced. Sooner or later the battery will loose its charge faster when being used. Poor maintenance can also be costly. If you’re using wet cells did you forget to add water to the one of the battery cells? If you’re planning to use these types of batteries it’s critical to maintain the electrolyte or its life will be shortened. Proper charging procedures, monitoring voltages, and standard maintenance including inspections of all connections from time to time are very important for all auxiliary battery systems no matter what type of battery is used.

The starting and the house battery systems are usually isolated from each other by a relay, switch, or semi conductor circuitry. As I said at the beginning, if you use up the house battery system during the night it’s important to have full starting batteries.

Some owners who store their RV’s for long periods of time use a battery switch to isolate the battery off the system and even from one another. These heavy duty switches are designed to work with high loads and eliminate arcing when being switched.

Power panels, monitors, and switching systems can be somewhat expensive but so can losing a group of batteries.


A solar setup consists of a solar panel (or an array of panels), all the necessary wiring and a solar charging controller which serves as a regulator and monitor. I had one 50 and two 65 watt panels installed on the roof. In good sun I had no problems being back to full charge by noon provided that the only item running was the refrigerator. If the battery became slightly low due to running some extra equipment, a 30 minute charge from the engine would pump the battery up to a reasonable level. I am in the process of adding more solar in the near future. During a visit to SMBW, I had them install a plug for connecting a portable panel at the rear of the vehicle. I also upgraded the controller from the Specialties Concept model to the “Blue Sky” unit. The Specialties Concept controller was OK for my application at the time and I really liked the battery level indicator, but the blue sky has more modern technology that I will discuss below called Maximum Power Point Tracking.


This image shows the Specially Concepts Mark PV Controller on the left and the Xantrex Link-10 monitor on the right.


This picture shows the Blue Sky MPPT controller on the left also with the Link-10 monitor on the right.

The Blue Sky controller is now currently installed on vans with solar coming off the line at Sportsmobile. Because it incorporates MPPT circuitry, it was a major upgrade to my system. Here is one explanation on how MPPT basically works:

“The converter circuit generates an output current from the solar cell power source using a switch mode power converter. A control loop is closed around the input voltage to the converter circuit and not around the output voltage. The output voltage is allowed to float, being clamped by the loading conditions. If the outputs from multiple units are tied together, the currents will sum. If the output(s) are connected to a battery, the battery’s potential will clamp the voltage during charge. This technique allows all solar cells in an array that are producing power and connected in parallel to work at their peak efficiency”. Alright, that’s an old definition. Modern MPPT controllers basically convert useless DC power (that would normally be wasted) to high frequency AC, step it up or down as needed, and then invert it back to a useful voltage the battery likes. While in operation, a MPPT controller constantly adjusts to the variable panel voltage output caused by sun exposure and temperature which can change throughout the day.

Simple yet effective, right? OK, let’s just agree to say it works and get you more bang for your buck. This technology helps greatly during weak sun exposure such as overcast, fog and lower light conditions.

As I have said, everything is improved daily in the technological world. The solar and battery industries are changing fast. For more facts on solar, these links goes over the basics and more.

There are a few different solar panels to choose from and I have seen many rigs coming off the assemble line that have rack mounted panels. Unlike mine which are glued down to the rooftop, the rack mounted versions let air flow under the panel. This is good because the cooler the panel is, the better it will work. Maximum amperage to the battery is what you are looking to obtain, just remember to factor in the weight. Some solar panels can be heavy making the top difficult to lift. SMB used a thin light weight semi flexible set of panel from Solara of Europe on my van. Unfortunately these panels are no longer available. The newer panels are light but must be mounted in an aluminum frame. Some people have the panels hinged allowing them to point or tilt toward the sun to maximize their output. Just a small shadow can reduce panel efficiency big time. There is overkill in some options, but with solar, more is better if you can swing it. As I alluded to in the previous writings, my three panels have kept up with the routine draw I pull utilizing a single 4D battery in clear to semi clear skies. But thick tree cover, fog, or heavy overcast will definitely lower the charge rate. This is where more is better. For individuals who are on the road frequently, a super array isn’t really necessary because your vehicle will bring the batteries back up during the drive. One thing solar does help with is to keeping the house and starting batteries up to par when the van sits idle. Even a single 120 watt panel can help here. It increases the house batteries life as well as keeping the starting batteries from going dead. With just a few amps and enough sun, most batteries should stay topped off ready to go. Of course leaving something on that pulls more amps than what the solar puts out can still drain all your batteries. For those who store their vans under cover keeping sunlight off the panels, it would be a good idea to have a battery cutoff switch installed to prevent battery discharge. A small trickle charger can keep up the batteries if needed. Carbon monoxide detectors might pull down the house batteries and a vehicle alarm can do the same to starting batteries if the van sits for long periods of time. Then of course there is the “my God I left that on” blunder. Unfortunately there are several ways to kill one or both of the DC systems that owners need to be aware of when the van sits. The separator is supposed to protect one or the other battery banks, but even loosing one battery is undesirable. This is where an isolation switch or device that totally disconnects the batteries from everything becomes helpful when the van is stored or not used for a stretch.

Here is a list of a few things that commonly kill SMB battery systems:

1) Already stated, the detectors pull very low amperage but enough sun and solar or a trickle charger will usually will offset the loss and keep the batteries up.

2) The radio switch. Most builds have a switch located in the mid section of the van that allows the radio to be turned on without the ignition key to be set to accessory. It’s handy but easy to be left in the on position especially if the radio volume is off or the radio is set to an active function. Furthermore added amplifiers pull a fair amount of current even with no music playing.

3) An inside light. Some 12v lights can pull over an amp. If left on, they can be difficult to see lit up during daytime. Most vans come with several inside lights in the cab area. Even the dome lights can kill the batteries within several days.

4) An outside light. Most vans also have outside lights or porch lights. Just like an inside light these too can take down a battery over a few days. It’s amazing what a little light can do. Obviously head lights are a big reason folks become stranded with dead batteries, but the backup and fog lights (if you order them) are often wired where they can be turned on without the engine running. This is so you can set up camp without bugging other nearby campers with a noisy engine running. Twice I left my fog lights on during daytime after exiting the vehicle. I now have them wired to the accessory and ignition circuit.

5) The fresh water pump has nailed me on one occasion. At times it will cycle on and off if the switch is left in the on position. This doesn’t do the pump any good either. My solar kept the house battery up even though the pump cycled for over a week.

6) The Starcool fan motor set to low is difficult to hear and runs even with the engine off. This is so the fan can be turned on while plugged into shore power and the 110 air conditioner is being used. (See part 9).

7) The inverter and refrigerator can also kill your batteries but are generally easy to spot in the on position.

8) An air compressor might not cycle on until the pressure drops low enough to activate it. At least most compressors such as the Extreme Air and ARB air locker pumps need the engine running to operate. Compressors should not be able to activate with the ignition turned to the accessory position because of this.

9) Anything that can consume power must be taken into account.

Other things like shorts and malfunctions can screw things up, but actually its rare when something is left on that kills your batteries. Monitoring the batteries is important but overall a well designed solar system not only helps to extend stays in the backcountry, it also helps in maintaining the battery systems health and longevity by keeping the batteries topped off at their float level. Remember that a high grade battery charging system might better suit owners that store their Sporto’s in the dark, but a solar array is a big plus to have while living it up in the backcountry.

Wire harnesses:

Now if you don’t want to install a solar setup, can’t afford it, or flat out don’t think you need it, a solar pre-wire job should be done. This is well worth the cost and if you ever change you mind it will be cheaper to install a solar setup. This is a big selling factor down the road.

One of those “I wish I had done that things was to have a heavy duty circuit installed that could be used for lights (or any DC item) on top of the van. Many people like the idea of high intensity lighting on top. Personally I feel these rigs are tall enough and this is one more object for trees limbs to grab. Dealing with equipment on top has been difficult during a few of my off road adventures. But this is another selling point for down the road and who knows, I might change my mind as well. Currently I’m thinking of pulling my Yakima cargo rack off and installing a lower profile rack that has a solar panel which can be removed when I need to haul equipment on top. An extra solar panel mounted on toward the rear would be valuable as would a few spot lights.


As stated earlier, inverters change your batteries direct current (DC) voltage to alternating current (AC) voltage that is used by common household devices. It’s important to size the wattage to the load you wish to run. SMB offers a few to choose from, but there are many companies who make inverters. Some models will also charge your house battery system. Inverters are available in a variety of sizes but SMB commonly installs units in the 1000 to 2000 watt range.


I preferred the Xantrex Prosine 2000 watt model because of my cameras and computers that need pure clean AC power. The Prosine produces power that is usually cleaner than what you’ll find in your own home. Another nice feature of this inverter is it has a control panel (shown here) that does help while trouble shooting an electrical problem. The Trip-Lite would be fine for most standard applications and it’s over half the cost. The link below will give some basic information on inverters. You can have any model or brand installed by SMB but be aware they are less knowledgeable about types they don’t often use. Just make sure you understand what the inverter is capable of. Anytime something is installed that is unfamiliar to Sportsmobile, there is a chance of a problem occurring. What’s the saying? Measure it twice and cut it once. Face it, sometimes things go wrong and working with established products that SMB typically installs lessens that from happening. Many owners install their own inverters. I know a few who have installed cheap units only to be disappointed in how it performs but a small backup inverter can help in some instances.

Power Plug locations:

Before construction is the time to think about any extra power plugs you need on board. I regularly plug in a battery charger to replenish a battery pack I use around the camp fire. I wish I had an AC outlet mounted behind the passenger seat so I don’t have to climb in the van to plug it in after every use. I also had an AC and DC outlet placed at the back of the van. Outside plugs are also a consideration. I had one AC outlet put in the outside utility door and use it to jump start vehicles via a starter/charger I carry. I have a couple of 12 VDC plugs here as well. It is the best spot to hook up power tools or electrical equipment while keeping the van doors closed. Speaking of the outside utility door (more commonly called a propane door), even though I do not have propane, this door is where all my power and water hookups are located. It’s a clean, neat area that I prefer over the external plugs and ports.


Some owners who have vans coming off the line eliminate much of the AC system. I have seen a few builds that have a single outlet which is usually located in an easy to use spot. Many people feel they don’t need multiple outlets. But being most refrigerators operate on AC and DC, and because they run more efficiently on AC, it’s advisable to run a 110 circuit to that area. While using shore power my refrigerator does not use the inverter for AC power. While disconnected from shore power it switches over to DC even if the inverter is activated. This seems to be the norm in construction. The microwave on the other hand requires the inverter to be turned on to work while disconnected from shore power. The outlets that feed the refrigerator and microwave are located behind the cabinetry and are usually not accessible to use for other items.


I ordered the microwave, and although it’s not used a lot, there’re handy. It does take up valuable cabinet space but I also store my paper plates or anything I can stuff in it. It’s best to run the vehicle when using the microwave or the battery will be pulled down fast. Low settings or running it for limited amounts of time is possible with a good battery reserve but microwaves pull huge amounts of current and care must be taken. Of course if you have shore power available it’s a very convenient appliance.


One question that comes up a lot is where’s the generator? I usually explain my distaste for the noise they produce, but there are some who like camping in spots where the sounds of generators fill the air. Well if you like these type areas, fire up the generator and join the crowd. My gripe with some people is their disrespect for others in quiet areas or ignoring rules dictating when generators can be operated. IMO there’s no difference in noisy engine than a stereo blaring music that I hate. But in many situations generators can be a nice accessory. SMB offers a few models to choose from; unfortunately I don’t have any information on them. A few 4X4 owners who run generators claim there is no one around to hear the noise anyway. This might be a viable solution for some folks. One really nice thing by having a one would be the ability to run an air conditioner in hot climates (provided the wattage is rated high enough). My Starcool requires a 3000 watt generator to run it. That would be a real plus, and I have put some thought into it. The problem is where to mount something that large. More than likely you will have to design a custom box for the rear bumper to store it. Space is critical and a decision must be made. I have been told the newer A/C units Sportsmobile now offers run off a 2kW generator but I would verify this. Other considerations for caring a generator would be weight, theft, and fuel type. For instance, it might be inconvenient to carry gasoline on a diesel van. All in all, a generator does have some good values.

Antenna’s GPS, TV’s, Audio equipment, and more:

I really try to avoid camping around people, but if I do hit a full service campground I can plug into cable TV. I had cable routed into the van from the propane door. I do carry a small outside antenna I can hook up to this outside port There are times I have watched TV when close enough to receive a signal. SMB offers a TV antenna that is mounted in the roof. It’s expensive and I felt it was not worth the cost being it’s hard to find a signal where I usually camp anyway. I have yet to even think about satellite TV. Hum… the Super Bowl in the hills? I will plan to upgrade my video TV

Back to antennas, I had SMB install a GPS receiver on top of the van to be used for navigation. I use Map-Tech software on the lap top computer mounted at the doghouse. Map-Tech has TOPO maps which can be viewed in 2 or 3-D. The tracking feature is very helpful and has gotten me out of a few jams by showing me the way I came into an area. I also run other more standard GPS road programs that are suited for highway travel. There are some really nice GPS systems out there and these systems continue to improve from year to year just as the software does. Like I said, whatever system you decide on, it should have the ability to mark trails on a topo map. This makes back tracking easy. Return during evening hours or even years later to re-run the same trail is very helpful.

There are systems to install as in-dash units but I decided on a universal laptop mount made by Ram. It was reasonably priced but there are some nice mounts out there that really kick butt. It all depends on what you want to spend.

What about audio/video equipment? Being it’s an electronic item I’ll go over it now even though it’s actually toward the end of the SMB construction list. SMBW has a company that installs audio and custom video systems. Rob and Randy are great to work with and know their stuff. I’ve seen some really nice setups but again, due to the cost, I passed by on a high tech video system and bought a standalone DVD/TV player. I wasn’t sure how well a nice monitor would hold up to off road travel and didn’t want to take a chance. I do plan to upgrade my video equipment very soon after the FCC signal change to HD comes about. One thing to take into account is how much a video system will pull. Some LCD 12v TV’s can pull as much as 10 amps. It’s important to make sure what the system will do to your battery supply. Although some may have the idea that heading to the great outdoors means leaving behind the ordinary helter skelter of everyday life, I enjoy watching a movie at times while on the road. Here is a link to a good selection of 12v TV’s and DVD players.

In contrast to my TV setup, the stereo system was something I upgraded from the start and I even added to it this year. During the initial construction Randy installed a sub-woofer and amp. Lately I had another amp put in along with a Kenwood stereo CD player. Now I can hook up my I-Pod and don’t have to carry all those CD’s which took up so much space. And with the new laws in California concerning cell phone use, the stereo recognizes my phone for hands free operation. I did have the microphone moved from the dash to the visor area which really improved the sound quality for those on the other end of the phone.

Randy also installed the alarm system while the van was being built. I don’t know too much about top quality alarms but the one they installed has worked well. I had a guy knock out my passenger window and it scared him off. But I think I might have an Auto Pager alarm installed. I have one in my pickup and it sets off an alert tone on the remote so you know if somebody is messing with the vehicle. It’s helpful when you can hear the remote warning you something is going wrong outside on your ride.

The last item in this section is the CB. I had the K-40 antenna and a Galaxy radio installed. I have traveled with Lloyd who also has a CB in his vehicle and it was great during the long ride being able to shoot the shi…well, have a lengthy conversation. On the highway it has helped by giving me an idea where CHP’s lurk. It’s also handy for rudimentary help (i.e. location of rest stops, diesel, restaurants, etc) or the possibility of oncoming road hazards, and conditions. Just be ready for the language. On one highway trip a trucker yelled “there’s a %#$! aluminum ladder in the north bound lane”. That incident probably paid for the CB itself. Actually the true reason I put in a radio was because every now and then off road rally guides require you to have a CB or other type communication radio so they can give directions. As you see there are several reasons for a CB but some owners install other types of communication equipment such as Ham radios which generally require an FCC license.

A few non-listed items:

Although switch panels are not on the SMB production list, some owners have had really nice panels installed. They’re a way to keep the cockpit clean and aid in turning some items on and off. Most of the switches SMB installs are located below the steering wheel where it’s possible to accidentally hit them with your knee. It’s kind of difficult to access that area down there as well as being able to see what’s on or off. A lighted panel strategically placed can make life easier while driving.

Another item I added to my install was satellite radio. I signed up for Sirius radio that is now Sirius-XM radio. After the merger I planned to drop the service but the station programming seems to be improving. Being able to hear music I don’t carry with me is great even though it’s hard to find the satellite itself from to time. This happens when using a portable receiver and stationary antenna the majority of the time. Trees make it difficult to capture the moving spacecraft at times especially in the California Sierra’s. Sooner or later the satellite will move behind a large tree and the signal will cut out until the antenna is re-directed. This can be frustrating if you like to camp in thick cover like I do. Funny because I’ve never had any problems in steep canyons at Death Valley, and during a trip through Nevada, Utah, Colorado, Wyoming, and Idaho, I almost never lost signal even in heavy tree cover. As soon as I got back to the Sierra Nevada’s the signal cuts out from time to time while driving on roads or sitting around the camp fire. I’m sure it has to do with the low angle on where the satellite crosses the horizon but even with that I plan to keep the service. Besides having to get up out of my chair to move the antenna just gives me one more reason to grab another beer.

Electronics and electrical products are always improving in the marketplace. It seems like there is always something cooler to install on my van and there are times I don’t want even look because I know I’ll want it. But by and large I have my van tweaked to suit my needs. After all it’s only money.

Thanks for following Autoramblings.