Electrical System in our DIY RV Camper Van

The electrical system in our van required the most planning and thought of any aspect of the camper van project. The electrical system is unique to each van, since everyone uses their van differently and has different goals and preferences.

We had some previous RV experience, so that was helpful as we planned our van design and systems. Electrical power is typically referred to in amp-hours at 12 volts. True deep cycle batteries are preferred in order to maximize life and capacity. Some opt for lithium batteries, but we did not want that higher cost and complexity. We chose to use the tried and true 6 volt golf car batteries. We would need multiples of 2, since two batteries in series would be need to make 12 volts. The 6 volt batteries we chose from one of the wholesale clubs were 215 amp-hour rated batteries, in series, two batteries would be 12 volts at 215 amp-hours. The rule of thumb is to not use the batteries below a 50% state of charge (SOC) in order to prolong battery life and the number of usable cycles. It is possible to go below 50% SOC, but this results in a lower voltage that might be an issue for some appliances.

Two 6 volt batteries like these would provide just over 100 amp-hours of power in our camper van project. This could be using 1 amp for 100 hours, or 4 amps for 25 hours. After looking at our intended loads (parking heater, refrigerator, inverter, lighting, fans, etc.) we decided that amount of power would last just over 1 day with no extra charging. We wanted to be able to camp for 2 days with no charging in order to still have power if we did not drive the van or have sunny days for solar charging. For these reasons, we opted to purchase 4 of the 6 volt golf batteries. We would connect two batteries in series, the other two batteries in series, and then those two 12 volt pairs in parallel. This would provide 215 x 2 or 430 amp-hours of power at 12 volts for the camper van. We would expect this setup to give us at least 2 days of power with our design.

We built a battery box out of baltic birch plywood using wood screws and wood glue. This box was custom sized to fit under our small bench sofa seat behind the driver seat. We installed anchor points that were bolted through the van floor, and then installed a seal and cover, vent hoses, and battery box lid. We tied it all down with a hefty ratchet strap. It is important to try to secure these heavy batteries well in case of an accident.

For battery charging, we opted to primarily use solar power for this task. A general rule is to have 1 watt of solar power for each amp-hour of battery power. Since we had 430 amp-hours of batteries, we were hoping to install 400 watts of solar panels on the van roof. However, we already had one 100 watt panel, and our desire to install a roof air conditioner and power vent would make this a very tight fit. We decided that 300 watts of solar power with an option to charge from the van alternator would be a good compromise. We installed three 100 watt solar panels in parallel. Installing them in parallel would allow one or two panels to charge our batteries if one or two panels were shaded and not able to output energy. We used connectors to merge the three panels and brought one set of wires into the van from the roof. We had good luck in other RVs with the Bogart solar charge controller, a PWM type, so we moved that to our camper van. In good conditions, this provides 16 amps or so into our batteries. If we get 5 or 6 hours of sunlight, then we can put 80 amp-hours or so back into our battery system. We estimated that this would usually be enough to replenish a day of power use.

To allow alternator charging when the engine is running, we installed two 40 amp relays between the solar panel incoming wires and the solar charge controller (Bogart SC-2030). We also run heavy wires from our van chassis starter battery to the relays. The relays are powered by a wire from the van ignition. When the ignition is on, the relays are energized and switch over to charge from the van engine electrical system. Either the solar panels or the van alternator provide power to the solar charge controller, which then regulates the voltage and current to the batteries. We also put a switch in the wire from the ignition, and this allows us to turn off engine alternator charging if it is not needed or if we have plenty of sunshine.

We also have one other battery charging option, and that is via shore or campground plug-in power. We installed a WFCO Electronics WF8935PECB 35 Amp Converter/Charger to distribute 120 volt outside power and to distribute 12 volt battery power. This unit has space for 11 fuses for our 12 volt circuits. It also has room for a main 30 amp 120 volt breaker and 4 other 120 volt circuits. Finally, it has a built-in 35 amp charger for our 12 volt batteries. It is not an intelligent 4 stage charger, but it can do some battery charging when necessary. Again, we prefer to use solar charging with our smart solar charge controller when possible. To bring outside power into the class B RV van, we installed a 30 amp plug in our back bumper. This allows us to connect a 30 amp cord we carry inside our back rear doors.

For our 120 volt appliances, we can power them from the WFCO distribution panel or using our 1500 watt inverter. We kept the cables from the battery to the inverter very short. It is also necessary to using a wire gauge calculator to make sure that the 12 volt wiring for all circuits is properly sized. The inverter has a remote on/off switch and two outlets. Our inverter is then connected to our 120 volt receptacles to power our microwave, television, hair dryer, electric cooktop, or water heater when we have not driven the van recently enough to have hot water. The air conditioner is too much of a power hog to easily run off batteries, so it is only used when we are camping and have shore power available. The inverter can only power one of the 120 volt items at a time, but it has worked very well for us with over 50 days of camping so far this year.

On the 12 volt side, our largest appliance is the TruckFridge TF-130 refrigerator. This has a true 12 volt Danfoss compressor, so no inverter is necessary. We see it use 25 to 35 amp-hours per 24 hour period normally. The wire size calculator showed that we needed 8 gauge (awg) wire since it was on the other side of the van from our 12 volt fuse panel. The surge current on startup can be around 10 amps.

Next, our diesel parking heater (air heater) uses around 8 amps during startup. We chose to not use propane in our van design, so we had to come up with different solutions for heating the van interior and heating water than a propane van might use. The diesel air heater works very well, and uses a very small amount of diesel fuel when heating. Once it is started, the current drops down to 1 or 2 amps to run the blower and electronic controller. We have a diesel heater blog post if you are interested in more details.

For normal ventilation, we chose to install a fan in the class B camper van roof. The Maxx Air MaxxFan Deluxe with Remote was our choice. This fan can be operated in the rain and it can pull air in or exhaust it outside. The fan was installed above our rear bed, and the remote control makes it easy to turn the fan on or off from the RAM Promaster front cab seats. We also installed two Sirocco II Fans from Seekr by Caframo to move air inside the van. We mounted one by the rear bed and a second one above the bench sofa behind the driver seat. All of these items draw minimal power, but it all adds up.

For our lighting, we did quite a bit of research to determine what might work best for us. We selected dimmable LED lights for overhead. We installed 6 of them in our wood plank ceiling. The are controlled by an on / off switch and an LED dimmer installed in the foam block behind the passenger headrest by the slider door front opening. This has provided plenty of light for general tasks.

Other lighting needs are fulfilled by dimmable touch LED reading lights. We have two of these over the rear bead on the head side. We also have another gooseneck reading LED light over the front sofa bench. To help light the galley counter top, we installed dimmable LED strip lighting under the overhead cabinets. We also installed a dimmer and strip LED lights under the cabinet over the bench sofa seat for use when reading or eating. The wet bath is lit by a LED light which illuminates blue then white that has an integrated switch. Finally, we installed LED light units under the bed to illuminate the garage / storage area. These are very nice when filling our fresh water tank or loading the folding bikes after it has become dark.

All of our electrical related controls are mounted on the side of the wardrobe cabinet next to the front bench sofa. This keeps any light from the controls from shining towards the bed at night, but it makes them easy to access during the day. The battery meter from Bogart can also be seen by the passenger when driving. The controls in this location include the inverter remote switch, the tank level monitoring panel, the diesel heater control, and the Tri-Metric 2030 battery monitor. This battery monitor easily shows the percentage SOC on our batteries. We can also see current in or out of the batteries, solar current, battery voltage, and amp-hour readings. It is a basic unit, but more than adequate. Once we have been on a few trips, we really only need to know the State of Charge (SOC). The more complicated and expensive battery meter options are not worth it to us.

We used a spreadsheet to list all of our AC (120 volt) and DC (12 volt) circuits. This made it easier for us to determine current requirements, wire gauge size, how many circuits we would need, and so forth. The total amps from 12 volt DC circuits determines what my wire size should be from the positive bus bar to the WFCO distribution panel (AWG 6 in our case).

DC (12 volt) Circuit List:

Circuit #	Item	Fuse (A)	Wire Gauge	Nominal Load (A)	Max Load (A)
1	Roof Vent Fan	10	12	5	9
2	Water Pump	7.5	12	4	6
3	Refrigerator	15	8	5	10
4	Heater	15	14	2	7
5	Pass Side Lights / Fan	10	14	2	3
6	Driver Side Lights / Fan	10	14	3	4.5
7	Pass 12V Accessory	15	12	6	12
8	Driver 12V Accessory	15	12	6	12
9	Pass Extra Circuit	15	12	5	10
10	Driver Extra Circuit	15	12	5	10
	TOTALS			43 A	83.5 A

AC (120 volt) Circuit List:

Circuit #	Item	Breaker (A)	Wire Ga.	Nominal Load (A)	Max Load (A)
1	Roof Air Conditioner	15	12/3	6	12
2	Wardrobe Outlets	15	14/3	5	10
3	Microwave, Galley Outlets	15	14/3	5	10
4	Water Heater, Rear Outlets	15	14/3	7	10

We also found it quite helpful to draw our entire electrical power system as a schematic diagram. This allowed us to easily see all of the major components to purchase and how they would need to be connected. I have included the figure below, click on the image to see a larger version. Based on this diagram of our camper van electrical system, I have built a list of most of the electrical components that we used along with links to find them.

Click the image above to see a larger version, and then you can use the list of parts below that we purchased and used in our camper van build. This may not work exactly for you, so please do your own design and planning work for your specific power needs. I include these to make it easier for some to do their planning, since these items are working well for us. It is also important to determine your proper wire sizes. Depending on the wire lengths, our wire gauges may not work for your project and could cause a fire if not properly sized.

Solar Panel & Charging System:

Solar Panel	100 Watt 12 Volt Polycrystalline Solar Panel (we used 3)
Charge Controller	Bogart SC-2030 PWM Solar Charge Controller
MC4 Connectors	Solar Branch Connectors Y Connector for Parallel Connection
Solar Extension Cables	8 AWG Pair 20 Foot Solar Panel Extension Cables (from MC4 connectors to inside of van)
Cable Entry Glands	3/8 Inch NPT Black Right Angle Nylon Cable Gland Strain Relief with Gasket (for running solar cables through metal roof, need 2)
Panel Mounting Brackets	Solar Panel Mounting Z Brackets, Set of 4 Units (need 1 set per panel)
VHB Mounting Tape	3M 4941 Very High Bond Acrylic Foam Tape, Double-Sided, 1″ Width, 5 Yard Roll (need 2 feet per panel, adheres bracket to van roof)
Stainless Screws	Stainless #10 X 3/4″ Hex Self Drilling Sheet Metal Screws (we used 1 per mounting bracket, in addition to VHB tape)
Roof Sealer	AP Products 017-90891 White Sikaflex 221
30A 12V Breaker	30 Amp Surface Mount Circuit Breaker, 12V (for positive solar cable from panels)
40A 12V Breaker	40 Amp Surface Mount Circuit Breaker, 12V (for positive cable from vehicle battery)
12V Relays	Automotive 30/40 AMP Relays SPDT 12V Bosch Style (2 used to switch between panels and alternator charging, leads kept very short)
6 Gauge Wire	6 AWG 25 Feet Black / Red Welding Pure Copper Flexible Wire (used to connect alternator to relays and solar charge controller)
Rocker Switch	SPST Round Dot Lighted Toggle Switch 20A 12V (used in control wire from ignition to relays)

Battery and 12V Power Distribution:

6V Batteries	Duracell Golf Car Battery – Group Size GC2, 6V, 215Ah (similar to Trojan T-105, we used 4, two series pairs in parallel for 430 Ah)
Battery Disconnect	Battery Switch, 12V Disconnect Master Cutoff Switch, 275A
Bus Bars	4 Post Power Distribution Block Bus Bar Pair with Cover, 250A (used red for positive bus, black for negative)
200A Fuse	200 Amp ANL Fuses Gold Plated (used 2)
Fuse Holder	0/2/4 Gauge ANL Fuse Holder (used 2)
Meter Shunt	500A, 50mV Shunt for Bogart Trimetric TM-2030 Battery Meter
Battery Monitor	Bogart Engineering TM-2030 TriMetric Battery Meter
100A 12V Breaker	100 Amp Circuit Breaker with Manual Reset, 12V (between positive bus bar and 12V distribution panel)
Distribution Panel	WFCO Electronics WF8935 Converter with 35A Charger (Distribution panel for 12V DC and 120V AC circuit power)

AC (120 volt) Power Components:

30A Breaker	30A 120V AC single pole circuit breaker for distribution panel main
20A Breaker	20A 120V AC single pole circuit breaker for roof air conditioner
15A Breaker	15A 120V AC single pole circuit breakers for other circuits
Power Inlet	RV Power Inlet, 125V, 30A, twist lock (mounted to rear bumper for shore power)
Power Cord	RV Extension Power Cord Twist Lock, 30 Amp, 25FT (plugs into shore power)
10/3 Wire	30Amp RV Extension Cord, 10 Feet, Black (cut off ends, use wire for Inverter to Panel and Shore input)
12/3 Wire	12/3 Romex residential indoor electrical wire (also marine 12/3 can be used) – for roof AC unit
14/3 Wire	14/3 Romex residential indoor electrical wire (also marine 14/3 can be used) – for other circuits
Inverter	Krieger 1500 Watts Power Inverter 12V to 110V, Modified Sine Wave Car Inverter (includes fuse and install kit)
Roof Air Conditioner	Coleman Mach 8 Cub Plus, 9,200 BTU air conditioner unit (must be on shore power to use)
Cook Top Burner	Electric Single Hot Plate, Portable Stove,1200W Infrared Single Burner (can be used with the inverter)
TV	24″ LED Television (can be used with the inverter)

DC (12 volt) Major Appliances and Components:

Refrigerator	TruckFridge TF-130, 4.5 cu ft, 12 volt Danfoss compressor (blog post)
Air Heater	Diesel Parking Air Heater Kit – no propane solution (blog post)
Water Pump	Shurflo 4028 Water Pump – 2.3 GPM (blog post)
Roof Vent	Maxx Air MaxxFan Deluxe Fan Smoke Cover
Fans	Sirocco II Fan from Seekr by Caframo, 12V /24V DC, Gimbal Fan for RV, Black

Other DC Items, Lighting, etc:

Ceiling Lights	RV Recessed Ceiling Light 4 Pack Slim LED DC 12V 3W Full Aluminum Downlights, Warm White
Ceiling LED Dimmer	12 Volt DC Dimmer for LED Lighting
Reading Lights	Dimmable Reading Light Gooseneck LED Task Light
Wet Bath Light	5 inch Dimmable RV White Ceiling LED Light
Under Cabinet Lights	12V LED Strip Light, Flexible, 300 LEDs, 16.4ft Tape Light, Daylight White
Over Cab Storage Light	White LED 3.25 inch Round Camper RV Utility Dome Light with Switch
AWG 2/0 Wire	AWG 2/0 wire for inverter, batteries
2/0 Lug, 3/8	AWG 2/0 3/8″ terminal lug, crimp on copper
2/0 Lug, 5/16	AWG 2/0 5/16″ terminal lug, crimp on copper
6 ga Lug, 3/8	AWG 6 3/8″ terminal lug, crimp on copper
6 ga Lug, 5/16	AWG 6 5/16″ terminal lug, crimp on copper
2/0 Heat Shrink	Heat shrink tubing, 3/4″ for 2/0, red & black
6 ga Heat Shrink	Heat shrink tubing, 1/2″ for AWG 6, red & black
AWG 12 wire	12 gauge wire, red & black, 100 ft
AWG 14 wire	14 gauge wire, red & black, 100 ft
AWG 16 wire	16 gauge wire, red & black, 100 ft

I hope that the information on our DIY RV RAM Promaster class B camper van electrical system was helpful. It has been working very well for us in over 50 days of camping as of this blog post. Our battery state of charge (SOC) has never dropped below about 64%, even with several cloudy days on those travels.

We also created a YouTube video covering our electrical system details in the class B DIY camper van build. Click the image below to view it.

Happy Trails…