Tag Archives: solar


12V Fan Switch

Recently a fan was installed to cool the solar components, like controller, battery charger, etc. As it is not necessary to run the fan continuously, a switch can regulate its use.

Radio Shack sells this 12V switch with a ground (+), a power (-) and a accessory spade.

Right now there is a wire running to the batteries, a 12V socket, the fan and the switch that have to be interconnected.
First the red (-) fan wire gets a connector.

102103After crimping the tiny wire, a little bit of solder is applied for an improved connection.

100For increased longevity of these joints, this assortment of heat shrink was acquired from Harbor Freight.

104The fan wire plug is finished by adding the heat shrink.

After adding all the required plugs to the different wires, we move from the workshop to the van to make the final connections.

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110V Power Inlet


The van is internally a 12V system fed by solar panels, with some 110V outlets powered by an inverter. Only the battery charger needs access to an exterior power source. For this, a 15A power inlet is installed next to the rear door, on the passenger side of the van.


ParkPower 150BBIWRV 15 Amp White Power Inlet

25The area directly below the brake light is ideal, weren’t it for the fact that inside, that space is occupied by one of the rear speakers. The best location will be left of the bottom of the brake light.


34The instructions for the inlet indicated a 1-7/8” opening which required me to buy a new bi-metal holesaw. With all the tools at hand, I could start by marking the exact location of the hole.


67Because limited workspace inside, I was going to try to remove the brake light to have better access. Faced with some old seals, that I didn’t want to damage, I quickly decided otherwise.


89After some aligning and double checking, I marked the spot. As the location is very
close to the rear door, I made sure that the inlet could be accessed, while the door was opened.


1011Before turning to the holesaw, I drilled a small pilot hole.



With a starting point established, the holesaw went through the metal like butter.


1617It all worked out great. In less than half a minute, a perfectly round hole was established. Only a few rough edges remained.



A few minutes with a file, followed by my trusted sandpaper create a perfect finish.



Now the exterior fitting.


23And interior checkup.




28Final inspection shows that the extension cord is not obstructed by the rear door.


Since everything is a perfect fit, it’s time to put everything together.


29First cover the bare metal with some paint. I spray some paint in the cap of the spray can and dab it onto exposed metal.


30While the paint dries, I pull out the battery charger wire and prepare the components of the socket.


31First the outlet rear cover and the metal attachment ring slide onto the wire.


3233The wire is guided through the hole to the outside. I almost forgot a piece of heat shrink, but that is added before attaching the socket to the wire. The power inlet has a blank, black and green wire opening, as well as a silver, black and green connection screw, which makes it a foolproof installation.



The heat shrink is slid in place and heated for a perfect fit.


37After I applied Silicone II as a weather barrier, the socket is attached to the van with the metal ring on the back. Finally the outlet is capped with the included black cover.


3839Not necessary, but I also used the three included screws, mainly to cover the predrilled holes in the white ring.




The finished 110V power inlet.



12V Cooling Fan

The compartment under the bed that will hold the charger, controller, inverter, etc. is a small enclosure and needs some form of cooling.  I choose a 5” computer fan with thermal control, that automatically adjusts its speed as the temperature rises. Other considerations were low noise level (<18dB), high airflow volume (up to 42cfm) and low current (<0.2A).



8182The package includes the fan, the thermal sensor, an extension wire and some screws.


83Installation will be as high as possible, because that’s where the hot air is. I make a simple paper pattern of the opening of the fan and glue it with some spray adhesive, on the outside of the compartment.


8485With a Dremel tool, a rough opening is created and later sanded smooth. At the same time the screw holes are predrilled.


8687The fan is now installed directly under the 12V Power Socket with the 4 included screws.


Now we need an outside cover.


A solid, but thin piece of cherry will function as the base for the fan cover. A small piece of window screening material is applied to both sides of the cover and fastened with a few staples. Two screws hold it in place.


The toilet is still visible under the pull-out shelf; next to it are the 12V power socket and the new fan with cover. At the end of the bed, at the rear doors, is an entry light and a 110V outlet. The flooring is Trafficmaster Allure Ultra.



Having batteries, doesn’t automatically mean access to 12V. Thus, two access points are planned in the van. One 12V socket is located at the solar components (controller, charger, inverter, etc.) compartment, under the bed. It’s immediately next to the pull-out shelf and serves to power my laptop.

12V Power Socket

It’s a standard 12V power socket, that includes a faceplate and wires.



First a hole, the size of the socket, is drilled with a Forstner bit in the ¼” plywood. The hole sits at the top, right under the bed overhang and is largely out-of-sight.



The 12V socket is held in place by the round rear cover, which is screwed onto the main body. The thickness of the plywood prevented that, so I shortened the cover by removing a short length with a metal saw.


68Next, two little wood blocks were needed, to support the screws of the face plate. Each of them is pre-drilled to hold the screw.


69And then glued in place with some ordinary wood glue.


70The included wires are easily attached.


71The job is finished by adding the two screws to the face plate.


I recently pulled the 12V wire from the battery compartment, but for now, I hold off connecting it to the socket, as I also plan to install a 12V fan at the same location and connect it to the same 12V wire. The fan should supply some needed cooling to the solar components.



Another post on wiring of the van. Two heavier wire gauges will support the appliances to be installed on the driver’s side.



Most of the wiring has now been done on the passenger side, except for the #4. The focus is now on the appliances that will be featured in the row of cabinets on the driver’s side of the van.

For a while now, I decided to go with a small electric pump to power the faucet in the kitchen sink and the 12V NovaKool R4500 fridge for my supplies. As an option I would like to add a Propex propane heater for those cool nights. I will take a small risk by calculating the wire sizes based on these appliances, as I might go with different brands or better options. In addition, another 12V outlet will be fitted in the kitchen area.


As the fridge is the largest, continuous electrical consumer, a proprietary cable is chosen consisting of two individual 8 AWG wires, as recommended for distances up to 32ft (the actual length is approx. 25′).


The remaining pump, heater (1.4A continuous running), 12V outlet and some lights are to be connected to a separate 12/2 AWG run of wire.


3839The 12/2 wire at the top, is a double landscaping wire; the bottom two are 8 AWG single wires, all of them are stranded, as these are easier to handle than solid wires.


404142All cables start at the battery compartment and are partially led through the channel. Midway the landscape wire appears and is tucked away to the side.


4344When it reappears at the top of the channel it is guided through a preexisting hole and continues on top of the channel, towards the rear of the van.


46As I still have to remove both the ceiling and all of the opposite wall panels, I’ll leave the wires here, until I star working on the remainder of the van.


47The same process is applied to the #8 wires.


4849First along the channel to the ceiling.


5051Then to the rear of the van.


All the wires are labeled; they’ll be tied in place at a later time.


Only the #4 welding wire remains to be done; that is used between the batteries and the solar components, like controller, charger and inverter.



While working on the multi-use cabinet, I started with some of the wiring. Before I can continue building new cabinets, the majority of the electrical wiring has to be installed.

Battery Monitor

The monitor will be located on the wall next to the side doors and connected to the batteries with 4 small wires. A short piece of Cat5 cable will do the job, because the battery compartment is only a few feet away.

 monitor and battery compartment


1211The cable is guided through the door channel to the floor, where it will be connected to the battery bank at a later time.



The cabling is left as is, until the hardware is installed.


Battery Charger

Under the bed are two shallow window compartments, which are above the wheel housing. Adjoining is a regular compartment that will contain most electrical devices, such as charger, inverter and controller. It has a removable side-wall for easy access.


Because the wheel housing is in the way, any cabling will have to go through the shallow compartments. A hollow core separation will serve as a divider between the two spaces, while at the same time hiding the wires.


14The divider consists of two 1/8” plywood sides, one solid base and a top divided in three, for later access to any cables.


15The parts are glued together in several steps and sanded to final dimensions.


The divider easily slides in at one side of the compartment.



After fitting, a few holes are drilled on both sides of the compartment, that will accommodate the wiring.



After a final check, the divider is glued-in and reinforced with two nails.


2122The actual wiring is just a matter of pulling the Romex wire through the divider and along the wall towards the right rear brake light.

2526The wire is then connected to a 110V power inlet, that will be installed below the brake light.

An extension cord plugged into the power inlet at the outside rear of the van, will power the battery charger.




Power Monitoring

The introduction to off-grid power (upgrading to off-grid power, power storage and power generation) is concluded with a post about monitoring and maintenance. With all this knowledge we can finally begin with the installation.


Daily monitoring the off-grid system is crucial for the longevity of the system. Maintaining a sufficient battery charge will extend its battery life.

The displays need to be located where you will see them, as you will refer to them often, especially when you are learning to use all the components of the system.


Monitor charge and discharge of batteries

The battery monitor tells you what is currently happening with your battery and electrical system. This will tell you how much battery capacity is left, and will let you know when the bank is properly recharged. At a minimum, you need the following:

  • The ability the see cumulative AmpHours into and out of the battery bank, in DC Amps, with at least one decimal.
  • Battery voltage. Primarily, you will watch the voltage being applied to the batteries change as the different stages of charging occur.


Monitor battery status

Flooded-cell batteries require routine maintenance. You need to check the water level about once a month and the following tasks every 6 months: clean the batteries, test for resting voltage, equalize as needed and test the specific gravity of the battery cells.

Use a maintenance log to document each task. This will help you identify developing problems.

A detailed maintenance schedule can be found at Battery Maintenance.

Power Generation


After upgrading to off-grid power and power storage, this post elaborates on the available power generating tools for a small RV. The electrical calculations are comprised into a detailed schematic overview, that serves as the basis for the installation.


The extra power from the alternator can be directed to the battery bank, to give the batteries an extra charge while driving. You likely have to install a heavier alternator.
I plan to move little once at my vacation destinations and as my research indicated a possible limited benefit, I will forego this option at this time.

Power Grid

Staying completely off-grid (boondocking or stealth camping) is the goal, but as the situation may require, a visit to a campground is an opportunity to replenish some battery power.
The battery charger is connected to the 110V external power inlet, that in turn can be connected to a 15 amp electrical outlet with a heavy extension cord.
With 420Ah in batteries and a charger rated for 15%-30% of it, the IOTA DLS-55 55 amp charger would be a perfect fit.


With a van, storage is always a major issue. In addition, the fuel is dangerous and smelly.
Personally, I never understood, why one goes through the trouble of finding that one, exclusive location, to have it disturbed by the noise of a running generator.

solar panelSolar

Panels are largely maintenance free and prices are still coming down. They are a great solution for off-grid camping, with some limitations on cloudy or rainy days.
With 420Ah in the battery bank, a balanced system ideally requires an equal amount in watts (420W) as panels.
That poses the problem of roof space on a (cargo) van. On my current Dodge, the available space is limited to 100” to 130” lengthwise with a 50” width and that includes the installation of a fan. Most available larger and cheaper panels are approx. 60” x 40”; where two pv panels would suffice, no room is left for the fan.
A better solution is four 47” x 22” photovoltaic panels from AMSolar or equivalent, that occupies about 90” of the roof, with plenty left for a fan. A consequence is the lower voltage rating of these panels of about 18 volts, which reduces the benefit of a MPPT controller.


With the planned propane cooktop and heater, a small 300W pure sine inverter is more than sufficient to power small loads, like a printer or scanner. Most small appliances, such as laptop and cellphone, that are ordinarily charged on 110V, will all have their own more efficient 12V inverter.


While finishing the multi-use cabinet, the idea of installing an induction cooktop developed as a possible alternative. I have been cooking with induction for years now and the advantages over gas are great. Extremely safe and efficient. With a different solution for heating, I could eliminate the proposed undercarriage, propane tank.
One obstacle is the power it requires to operate. Research on the different forums, leaves the issue unresolved. To experiment with induction, a larger 1000W-1500W inverter is required.


RV Photovoltaic System Schematic


The calculated size of the battery bank, the number and size of the solar panels and the other derived equipment are all comprised into this simple diagram.

Click on the image, for a larger view.


Power storage


Now that the different parts of the electrical system have been established, the first thing to do is calculate the number of batteries needed to support the daily energy use. Here a lot of time goes into researching all appliances that will ultimately be installed. Adding up their amperage use, will yield our daily ‘electric bill’.


The choice of 6V deep cycle flooded cell batteries is mostly based on performance, availability and price point. The disadvantage of requiring maintenance and venting can be incorporated in the monitoring process, making it part of a schedule.

Walmart, Sams Club and Costco carry these ‘golf cart’ batteries, often at a very low price. The Trojan T-105 battery is a good alternative if nothing else is available.


Calculate battery bank size in AmpHours


basic formulas
Amps = watts / volts
1 amp AC = 10 amps DC


Calculating the energy requirements needs an inventory of all electrical appliances.


appliance amp/hr hrs/day ah
Induction cooktop 65.0 0.50 33.00
fantastic fan 1.9 4.00 7.60
propex heater 1.4 1.00 1.40
waterpump 2.0 0.25 0.50
novakool fridge 1.5 15.00 23.00
Inverter 0.7 0.50 0.35
laptop 8.0 2.00 16.00
fluorescent 15w light 1.0 2.00 2.00
led 34W light (4.5W) 0.5 2.00 1.00
battery charge controller 0.1 18.00 1.80
total Ah a day 86.65
conversion losses 20% 17.35
daily Ah need 104.00


Daily average RV use is less than 100Ah


Batteries should never be drained more than 50% of full charge. With an estimated daily use of 104Ah, a minimum battery capacity of 104Ah x 2 = 208Ah is needed.
Two 6V batteries @ 210Ah would suffice, while four 6V batteries @ 420Ah would provide 2-3 day buffer on rainy days.

Inverter Selection: Temporarily replacing the propane cooktop with an induction plate, requires a 1000W-1500W inverter.


batteries panels inverter
four 6V @ 420Ah optimally 420W 1000W-1500W


Phase in the installation:

  • Start with two 6-volt batteries.
  • Add a battery monitor with cumulative AmpHours.
  • Battery charger.
  • Medium size inverter to run the cooktop.

Expand your system as needed.



Upgrading to off-grid power

As I am struggling a bit to finish the multi-use cabinet,  the next phase of the van conversion will entail some of the wiring for the off-grid electrical system. Before any new cabinets are built, cables have to be laid. At the same time, buying a battery charger, inverter, some batteries and an induction cooktop, will give give me ever more use of the van, while the conversion is underway.


The current electrical system of the van consists of a few lights, powered by the van’s car battery. While I do not intend to live permanently in the van, my goal is to be completely self-sufficient on trips that might last up to a couple of months.
Upgrading to go off-grid involves power storage, generation and monitoring.

Trojan T-105Power storage decisions

  • battery voltage: 6V or 12V.
    6V batteries will generally perform better than 12V batteries. My choice: 6V.
  • battery type: deep cycle flooded cell, sealed flooded, gel, AGM or Li-Ion.
    Wet-cell is the cheaper alternative, but has the disadvantage of requiring maintenance and venting.
    AGM batteries have advantages, but carry a high price.
    Li-Ion are expensive and the DIY technology is still in its infancy. My choice: flooded cell.
  • battery capacity: enough capacity for your energy needs.
    Calculate battery bank size in AmpHours.

The Trojan T-105 battery is the standard, Sams Club golf cart batteries are similar and cost less. Four of them give 200Ah if drawn down 50%.

solar panelPower generation decisions

  • alternator:
    Will charge your batteries when you are moving. I plan to move little when at my destination. My choice: No.
  • power grid:
    Emergency power through battery charger at a campground. My choice: Yes.
  • generator to battery charger:
    Complete independence does not outweigh the noise and storage issues. My choice: No.
  • solar:
    Panels are largely maintenance free and prices are still coming down. A balanced system requires enough panels for the amount of amps in the batteries. Rule of thumb: 1 amp of storage for each watt of solar panel. Four Trojan T-105 batteries at 400Ah need 400W of solar panels. My choice: Yes.
  • inverter:
    A large one to run the microwave, etc. or a smaller one that only runs occasional small appliances. My choice: Yes (a smaller one).

monitorPower monitoring

  • monitor the status of the system.
  • battery monitor with cumulative amp hours. This will tell you how much battery capacity is left, and will let you know when the bank is properly recharged.

Daily monitoring your off-grid system is crucial for the longevity of its parts. Maintaining a sufficient battery charge will extend its battery life.