RV Tip: Troubleshooting a 12-volt DC Problem

!±8± RV Tip: Troubleshooting a 12-volt DC Problem

If you enjoy RVs you already know that a major part of the fun with RVing is getting away from everything. You can just pack up the RV and head out to get some well deserved rest and relaxation without having to deal with the hassles of day-to-day living. These restful, relaxing, memory making RV trips should not be jeopardized by something as simple as a 12-volt electrical problem ruining your vacation.

If you've been RVing for any amount of time you are already aware that a good portion of the devices and accessories in your RV operate off of 12-volt DC power. 12-volt DC or Direct Current is electricity supplied by the RV batteries. DC electricity flows in one direction, from negative to positive. 12-VDC electricity is stored in the RV batteries and supplies power for components, devices and appliances that operate off of 12-volts.

These 12-volt devices include overhead lights, the water pump, vent fans, furnace fan, range hood fan, LP gas leak detectors, stereos, 12-volt TVs and the refrigerator when it's operating in the LP gas mode. When you go camping you rely on these 12-volt items to operate properly, especially if you're dry camping without hook-ups. So what do you do when one of these 12-volt items quit working?

For the sake of an example let's say that we are dry camping and our 12-volt water pump quits working.

I am convinced that just about anybody is capable of troubleshooting a 12-VDC problem, and in many cases repairing the problem without it ruining your camping trip. For starters you will need a couple of simple tools to assist you in troubleshooting your RV's 12-volt electrical system.

1). An inexpensive 12-volt test light.

2). A multi-meter that can test for DC power.

Both of these are available at local auto parts stores. You should also keep some electrical tape, various size wire nuts, 12-volt light bulbs and 12-volt fuses on hand. Check the amperage of the fuses used in the power distribution box and keep an assortment. If you're aware of any inline fuses used on any of the 12-volt devices keep these on hand too.

Now, try to determine the last time the water pump actually worked. Did you leave the RV for a period of time with the pump on? Is there water in the fresh water holding tank? Were you working on or around something else that could have affected the operation of the water pump? Try to think of all possible scenarios. Something might jar your memory resulting in a quick fix to the problem.

If not, the first step is to verify that the coach battery or batteries are charged enough to supply power to these 12-volt items. There are a couple of ways to perform a quick test on the coach batteries. You can use the monitor panel to check the condition of the coach batteries. To get an accurate reading make sure the RV is not plugged into electricity and turn on a couple of overhead lights to place a small load on the battery. Check the reading at the monitor panel. (If you check the reading at the monitor panel when the RV is plugged in to electricity it will give you fully charged reading) A more accurate method is to test the battery with a multi-meter. Set the meter to read 12-VDC and place the negative test probe on the negative battery terminal and the positive test probe on the positive battery terminal. A fully charged battery will read in the range of 12.6 to 12.7 volts. If it reads less than 12-volts it is below a 50% state of charge and will need to be charged.

If the battery is fully charged, the next step is to make sure that any battery disconnect switch for the coach battery is turned on. If the battery disconnect switch is on, verify that other 12-volt devices in the RV are operating properly. If there is 12-volt power to the interior of the RV you need to check the fuse for the water pump in the power distribution center. Determine which fuse is for the water pump (fuses are normally labeled) and find a suitable ground for the 12-volt test light. Test both sides of the fuse for 12-volt power. If the test light only lights on one side of the fuse replace it with the proper size fuse and try the water pump again. If there was power at both sides of the fuse check for 12-volts at the water pump switch. If there is voltage, and the switch is operating properly check the water pump wiring for an inline fuse.

Find a good ground for the 12-volt test light and probe the wire on both sides of the fuse. If there is only power on one side of the fuse replace it with the proper size fuse and test the pump again. If there is power on both sides of the fuse check the water pump wiring connections at the wire nuts. It's possible for connections to come loose due to excessive vibration. Correct any loose connections and try the pump again. If the pump still doesn't work feel the motor to see if it is hot to the touch. If the motor is hot, a thermal breaker may have been triggered. Allow the pump time to cool off and see if it re-sets itself.

If you complete all of these tests and there is 12-volt DC power coming to the water pump motor, and it still doesn't come on, chances are the water pump is bad and it will need to be replaced.

Troubleshooting a 12-volt electrical problem in your RV is not that difficult. Follow the logical path of the device you are troubleshooting and see if you can determine where the problem is. It might be possible for you to save your well deserved vacation, some money and a trip to the RV dealership too.

Note: If you don't feel comfortable performing your own maintenance or troubleshooting the 12-volt electrical system, take your RV to a reputable repair center to have it checked out and repaired

Happy Camping!

Copyright 2006 by Mark J. Polk owner of RV Education 101

RV Tip: Troubleshooting a 12-volt DC Problem

Inflatable Bed Rails Guide

Solar Charge Controllers for Photovoltaic Panels

!±8± Solar Charge Controllers for Photovoltaic Panels

Photovoltaic panels are the consumer's choice.

With the price of carbon-based fuels on the rise, the power companies that rely on fuels such as coal and oil to generate the bulk of their electricity have been forced to raise their rates; subsequently, homeowners are now opting for solar power to satisfy their electricity needs. Photovoltaic systems are popular with homeowners because the energy is free and recent technological advances have reduced the initial cost of these systems.

Batteries require a steady charge.

Due to the intermittent nature of solar energy, it is not practical to connect appliances directly to a photovoltaic panel. Instead, the power absorbed by the panels during hours of sunshine charges batteries, where it is stored for use as needed. The output of photovoltaic panels depends on certain variables such as the location of the solar panels, the time of day, and the season. These factors all affect the angle of incidence of the sunlight striking the photovoltaic cells and consequently, the temperature of the cells. These dynamic conditions that cause fluctuations in the output power of the panels are not conducive to good battery health. As a general rule, batteries like to be charged at a current rate that is about 20% of their Amp-hour rating. For instance, a 10 Ampere charge would be ideal for a 50 Amp-hour battery. Since overcharging batteries can cause them to quickly fail, a solar charge controller is necessary in order to insure the proper charge current is maintained.

What is a solar charge controller and how does it work?

A solar charge controller is an electronic circuit that adjusts the output voltage and current of solar panels to match the needs of the batteries being charged. In order to charge a battery, your charger -- or in this case your solar panel -- must be at a higher potential than the battery being charged. In other words, the voltage of the panel must be greater than the opposing voltage of the battery under charge, in order to produce a positive current flow into the battery. But how much more should it be? The current flow can be calculated using Ohm's law: E=I*R; where E is the voltage in expressed in volts, I is the current in Amperes, and R is equal to the resistance measured in ohm's. The effective voltage in this circuit is the output voltage of the solar panel minus the opposing voltage of the battery. We can determine the difference in voltage necessary to cause our desired current flow by plugging our known values into the equation. Assuming a 12 volt battery with a 50 Amp-hour capacity, our target charge rate should be about 10 Amps. There is no resistor in this circuit except for the internal impedance of the battery, which is a fraction of an ohm. In this case we will approximate it to be 0.2 ohms. Using Ohm's law we multiply 10 Amps by 0.2 ohms and we get 2 volts as a result. This means that our solar panel must be 2 volts higher than our battery voltage to maintain our target charge rate. This example is meant to show that the rated output voltage of your solar panel must be greater than the battery being charged for your solar charge controller to work. As discussed earlier, the actual values are dynamic and thus the need for a charge controller. There are some very sophisticated solar charge controllers available today, which use maximum power point tracking, or MPPT, allowing them to adapt to different battery and panel combinations such as 24v, 36v, 48v, etc. These controllers use DC-DC converters to match the voltage and use digital circuitry to measure actual parameters many times a second to adjust the output current accordingly.

The proper charge controller is necessary.

As you can see, a solar charge controller is an absolutely essential component of any photovoltaic system. Although it is true that a simple functional charge circuit can be built with a few parts obtained from your local electronics part store, this option is not recommended for the average person. With so many variables associated with solar power, the use of a solar charge controller that has the ability to track all the pertinent parameters and provide the optimum charge for your batteries is recommended instead. The use of a quality solar charge controller will ensure that you enjoy the maximum life from your batteries and the most from your photovoltaic system.

Solar Charge Controllers for Photovoltaic Panels

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Cobra CPI 1575 1500 Watt 12 Volt DC to 120 Volt AC Power Inverter

!±8±Cobra CPI 1575 1500 Watt 12 Volt DC to 120 Volt AC Power Inverter

Brand : Cobra
Rate :
Price : $96.95
Post Date : Dec 25, 2011 21:12:29
Usually ships in 24 hours

This inverter provides household power on the go. It converts battery power to 120 V AC household power, allowing you to power up office equipment and household appliances from your vehicle. This unit is ideal for such appliances as microwave ovens (1000 watts or less), coffeemakers, laptops, TVs, video game consoles, CD and DVD players, cell phone chargers, and more.

Power equipment and appliances from your vehicle. Click to enlarge.

Great for automobiles, RVs, boats, tractors, trucks, and more. Click to enlarge.

Includes three grounded AC receptacles and 5-volt USB output. Click to enlarge.

How The Cobra Power Inverter Works
The Cobra power inverter is an electronic product that has been designed and built to take low-voltage DC (Direct Current) power from your automobile or other low-voltage power supplies and convert it to standard 115 volt AC (Alternating Current) power like the current you have in your home. This conversion process thereby allows you to use many of your household appliances and electronic products in automobiles, RVs, boats, tractors, trucks, and virtually anywhere else.

Cobra 1500 Watt Output Waveform
Some very sensitive electronic equipment might not operate satisfactorily on "square wave" or "modified sine wave" power. The output waveform of the Cobra Inverter is a "square wave" or "modified sine wave." It is a stepped waveform designed to have characteristics similar to the sine wave shape of utility power. A waveform of this nature is suitable for most AC loads, including linear and switching power suppliers used in electronic equipment, transformers, and motors.

AC receptacles
With three ground AC receptacles, you can connect and power multiple devices at once.

USB Output
The 5-Volt USB output allows charging and operation of modern portable devices, such as iPods, BlackBerrys, and cell phones.

Remote On/Off Switch Capable
An optional Remote On/Off Switch can be connected to the Remote Jack, allowing you to turn the Cobra power inverter on or off from a convenient location when the inverter is installed out of reach.

Safety Features
The CPI 1575 will notify you with a flashing meter and alarm sound when there is a power problem, and will shut down for protection in the following situations:

• Current Overload Protection--If the inverter is overloaded, it will shut down to protect itself.
• Short Circuit Protection--If the AC output of the inverter is short-circuited for one second or more, it will shut down to protect itself.
• Low Voltage Protection--If the input voltage drops to 10.0V or less, the inverter will shut down to protect itself.
• High Voltage Protection--If the DC input voltage rises above 15.0V, the inverter will shut down to protect itself.
• Over Temperature Protection--If the internal temperature rises to 40 degrees C (104 degrees F), the inverter will shut down to protect itself.

What's in the Box
CPI 1575 DC to AC Power Inverter, instruction manual

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