RV Electrical Systems
Most RVs have 3 electrical systems:
— Chassis 12 volt DC
— RV house 12 volt DC
— 120 volt AC circuit
They interconnect at various points to share power.
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Chassis Electrical 12 volt DC
The chassis 12 volt direct current (VDC) is charged by the engine alternator and recharges the chassis battery under the driver’s floorboards. Like a standard car’s wiring system, the chassis 12 VDC powers the engine starter, dash displays, vehicle headlights, vehicle computers, and other systems.
The chassis wiring is fuse protected with fuse blocks and relays located in various locations on the car. A large block is located under the driver’s seat pedestal, another under the passenger’s foot panel, and others are located in the engine compartment. I suggest carrying an assortment of blade fuses and the Mercedes Sprinter PDF file of fuse locations and functions. It is best to be prepared for when a fuse blows while driving at night, in the rain, while heading for the perfect boondocking spot. OK, maybe raining was too much.
TIP#213: In a pinch, you might be able to temporarily use a fuse of equal value from another unused function until you can get a replacement.
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RV Electrical 12 volt DC
The RV 12 volt DC house system includes the house battery, either flooded lead acid battery, AGM (Absorbed Glass Mat) or lithium and may be charged by a second, larger engine alternator, solar panels, on-board generator, or by campground shore power. The RV 12 VDC system powers interior lights, fans, heater blowers, water pump, television and entertainment system, refrigerator and more.
An option for a Li3 lithium battery is good if you do a lot of boondocking. The 600 amps can power the air-conditioner for 7-8 hours. If you prefer to camp while connected to shore power, the extra expense of a Li3 system may not be necessary. If you have a van with AGM batteries, it is fairly easy to swap them for small lithium batteries which will have much more power and are lighter in weight.
Charging the house battery and powering the circuit is accomplished in several ways. When using the generator or plugged into shore power, a large dual purpose Xantrex converts the 120 VAC into 12 VDC to charge the battery and power the 12 VDC circuit. A second function of the Xantrex is the Inverter which takes 12 volts DC and outputs a 120 volts AC for the 120 VAC circuits. To turn the Xantrex on/off, press the silver button. When running, you may hear the cooling fans running in one of the rear wheel well cabinets.
A large 260 AMP second alternator also provides charging to the house battery. On the roof are thin, flexible solar panels that generate electricity and send it to the solar charge controller and to the battery.
The RV 12 volt circuits are also fuse protected and a panel us usually located in the back of the RV. The Galleria uses blade type fuses like the chassis fuses.
To power the 12 VDC circuit on/off, a STORE/USE switch is located in the upper electrical cabinet.
FireFly
The Firefly control system uses touch panels to turn lights, heat and air-conditioning on and off.
See the Firefly section for more information: FireFly Control Panel
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Xantrex Battery Management System
The Xantrex Battery Management Supply (BMS) protects the house battery by shutting it off from the electrical system when it notices any problems. By reserving a portion of the battery’s capacity in regular usage, it holds an emergency energy reserve.
The BMS can gather data from the battery and display it on the digital interface in real time.
LED power button is off when the BMS is turned off and battery power is disabled.
LED power button is on when the BMS is on and battery power is enabled.
LED power button flashes rapidly when BMS is in alarm state and battery power is disabled.
The orange light on the system remote panel is illuminated when battery voltage is low (12% battery capacity left).
When SoC is between 10% and 3%, and the reserve shutdown event has occurred, press the Power button on the BMS and begin charging. Avoid using heavy DC loads like a 12 VDC air-conditioner when the battery is on heavy charge.
Do not charge the battery in ambient temperature below freezing.
The following is a basic outline of the BMS operation:
- Press the Power button to turn the BMS on. You will hear a click and the button will become illuminated.
- During charging, the BMS will allow charging if a safe voltage limit (HVC) is not exceeded. The charger may pause for several minutes during charging, this is normal operation.
- During discharging, the BMS will turn off when the RVC is reached. To use the 10% Reserve Capacity (reserve energy), press the Power button on the BMS to turn it on. If the battery has been depleted to below the safe voltage level it will not allow discharge.
- Press and hold the Power button for five seconds to turn the BMS off. You will hear a click and the button will no longer be illuminated.
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Solar Panels
Many vans have some solar panels on the roof to supply a small amount of power and keep the batteries fully charged. Our van has three 110 watt flexible panels that are connected to a GoPower Charge Controller. While this may sound like a lot of power, it is barely enough to keep the refrigerator running.
The charge controller regulates the solar panel current to keep the battery from overcharging. The GP-PWM-30-SQ, used in the Galleria, is rated for 30 amps and use a Pulse Width Modulation (PDM) and a four stage charging system.
In the electrical controls cabinet, is a solar ON/OFF switch.
A 20 amp fuse protects the circuit but I haven’t found its location yet. Probably by the battery.
Error Codes
b01 – Battery is less than 3.0 volts or has been disconnected.
b02 – Battery polarity is reversed.
b03 – Battery voltage is over 17.5 volts
b04 – Battery temperature is over 149 degrees F
For additional solar power, a set of portable panels can be connected to a connector in the external water connection box. It can add another 200 watts of power but will require its own separate charge controller.
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Cigarette Lighter Sockets
There are a couple 12 VDC cigarette lighter style sockets in the van including one that powers the television. An interesting fact is the TV is 18 VDC. Coachmen modifies the TV by adding a DC/DC 12 volt to 18 volt step-up converter inside the TV.
Other uses for the sockets are 12 VDC lanterns and camping fans.
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RV Electrical 120 volt AC
Like any home electric, the 120 volt alternating current (VAC) system powers the RVs larger appliances like the microwave, induction cooktop, electric heat, to name a few. 120 VAC is produced by either an onboard generator, shore power connection or supplied by the Xantrex Inverter/charger. These circuits use home style breaker switches located in a panel with the house 12 VDC fuses. Like a home system, there is one large breaker that can cut off all power to the other 120 VAC breakers. This does not cut the 12 VDC power. Also, in our Galleria, the main breaker does not shut off the Xantrex.
The 15 amp electrical receptacle outlets in the galleria are protected by a single a GFI (Ground Fault Interrupter) that will cut power if it senses senses more than a 4-5 milliamp of power going where it shouldn’t. This GFI is the first in line of a chain of plugs and when it trips, the others also loose power. The strange thing is, Coachmen places this GFI in the outside receptacle on the passenger side of the van. (Ours also has a label on it saying not to be used in damp environments. We replaced it with a higher quality GFI).
Troubleshooting the 120 volt AC
Power at the microwave but not at the plug-in receptacles, check the GFI on the outside, passenger side.
If you are not getting power to the van at all, the first place to start is the power pedestal. A very handy tool that everyone should carry is a non-contact AC voltage tester. This is a great tool to test the pedestal before even touching it to be sure it is safe. (see Hot Skin).
1 – Is the pedestal breaker on and using the tester, does the receptacle have power?
2 – Using the tester, check that your power cord has power at the end you connect to the van.
3 – Next, test the orange wires going into the Xantrex.
4 – Finally, hold the tester to the breakers in the fuse panel.
If the tester doesn’t indicate power at these points, you have located the failure.
When connecting to shore power, the Xantrex pass-thru should be powering the 120-volt AC circuits. The Use/Store switch controls the 12-volt DC and even when in Store mode, ours has power to the microwave.
There is a reset button between the fans on the rear of the Xantrex. I don’t know if this shuts off the pass-thru power.
The outside GFI only controls some of the inside receptacles (not the stove or microwave).
If you don’t have power at the breaker panel, then you have narrowed down the problem.
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Inverter/Charger
The Xantrex has several functions. The inverter uses the 12 volts from the house battery and inverts it into 120 volts AC.
When plugged into shore power, the charger function converts the 120 VAC into 12 volts DC to charge the house battery.
The cross-over function switches between the 120 VAC power generated from the inverter and house battery to the 120 VAC when plugged into shore. It effectively bypasses the Xantrex to supply shore power directly to the 120 VAC outlets.
The remote panel in the electrical cabinet can control Xantrex functions including setting the shore power amperage. For example: It is possible to set the amperage to from 30 amps, down to 15 amps and be able to plug the van into a standard home electrical outlet.
If you have the Bluetooth option on the controller, you can change settings from your phone or tablet. (If you don’t have the Bluetooth the controller is easily swapped for one that does).
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Generator
The Galleria comes with an Onan propane powered generator unless the Li3 package is selected. Gen Start and Auto Start is a feature where the generator will automatically start based on low battery voltage and/or a high temperature condition to power on the air-conditioner.
Generators, like the RV itself, don’t like to sit around and should be run every month or two for about 20-30 minutes to get the oil up to temperature. This will bake out any moisture in the oil and generator itself.
If the generator fails to start, there are several things to check:
– – Does it turn over?
– – Is the battery voltage enough to power the starter?
– – Is there propane in the tank?
– – Are the switches at the tank and in the control cabinet turned on?
– – Are you at a high elevation or extra cold environment?
– – If you have a propane stove, does it operate normally?
– – Check the breaker switch on the generator to see if it has tripped.
– – Check the oil level in the generator. There is a low oil cutoff to prevent it from running without oil.
– – Spark plug cable secure?
– – Replace the spark plug with a spare. You do carry a spare plug right?
– – Any mud-dabbers nesting in there?
– – When was the last time the generator was serviced? Recently: check for loose wiring.
– – Does it run but stops when a load is applied? Probably a good time to take it in for servicing.
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USB
I guess we should include the USB chargers in the RV. These operate from the 12 VDC circuit and output 5 volts to charge devices like phones, tablets, etc. If you are concerned with parasitic power drains, these USB chargers have about a 2 amp drain on the battery.
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This is a diagram we started making from our first Galleria (2020 24FL Li3). It’s just a little bit of the jumble of wiring in the fender box. Hopefully, we can get it completed someday.
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See webpage covering electrical hookup:
https://rvxplor.us/electrical-hookup/
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