The Complete Book of Boondock RVing

by Bill Moeller

  The consumption of electrical power by today’s cars and trucks is tremendous considering the need to power air conditioners, heaters, radios, CD players, and the addition of many new electronic components used by RV or truck systems. There is even talk of increasing automotive electrical power to anything from 24-volt to 40-volt systems. This of course would have a huge effect on RVing. It would mean changes in converters, inverters, batteries, chargers, and alternators, as well as the electrical systems within the RV itself. However, at the present time it is all a rumor that may never happen.

  BATTERY SWITCHES, ISOLATORS, AND COMBINERS

  Up to now we’ve focused on the alternator in relation to the house battery. But there is another battery involved in this system, the SLI battery, which is also connected to the alternator. Unless it is isolated from the house battery, the SLI battery will be discharged as the house battery is being used. We can resolve this potential problem with three different types of devices: battery switches, battery isolators, and battery combiners.

  Battery Switches

  A marine battery switch is one way to separate the house battery bank from the SLI battery in a motorhome. If you are knowledgeable, you can install one yourself. It has settings that allow you to switch from one battery to another. When discharging, set the switch so only the house battery bank is accessed; during charging, switch to the setting that allows both to be charged at the same time. This system works great—as long as you remember to change the switch to the proper setting!

  Unfortunately, battery switches do not work with tow vehicles and trailers because the switch must be turned to the engine battery for normal operation.

  Our battery switch, which we have only for safety. We can turn off all the batteries, which you can’t do in most trailers.

  Battery Isolators

  A second and more convenient method of separating the SLI and house batteries is with an isolator, either a solid-state diode isolator or a mechanical-relay isolator.

  Diode isolators allow current to flow in only one direction; in this case, from the alternator to each of the two battery banks, but not toward each other. The battery bank that needs the charge will receive it, and the other one will reject it. This isolator works well with both motorhomes and tow vehicles for trailers.

  The mechanical-relay or solenoid, isolator is activated by the vehicle’s ignition switch. When you turn on the ignition, the solenoid closes an electromagnetic switch that connects the SLI battery to the alternator circuit. The battery is connected to the alternator (and thus able to be charged) only when the ignition switch is in the On position. When the switch is turned off, the solenoid springs back, breaking the connection, thereby protecting the SLI battery from being drained as the house battery is being used.

  Each type of isolator has disadvantages. The solid-state diode isolator creates a voltage drop across the diode of as much as 0.6 volt or more. The alternator must deliver a higher voltage to compensate for the loss, which overworks it. Also the diode isolator can become very hot during use, so it must be mounted on a heat sink, which dissipates the heat.

  When selecting a diode isolator, make sure it is rated at a higher amperage than your alternator so the diodes don’t burn out. For example, use a 150 amp isolator with a 125 amp alternator.

  The mechanical-relay isolator uses a spring-loaded switch, and the springs can wear out and break, although they are quite easy to replace.

  When we purchased a new truck for our tow vehicle, we were dismayed to learn there was absolutely no room under the hood for installing an isolator. We were very perplexed by this, and finally decided to just attach the charging line to the alternator wire at the battery along with the engine battery wire. This has worked for us because we have a trailer, but it would not work if we had a motorhome because the engine battery is always connected to the house batteries. We must, however, remember to disconnect both the battery-charging line and the regular trailer connection plugs before we do any boondock camping or we could discharge the engine battery.

  Battery Combiners

  The latest type of protection for all battery banks is a battery combiner. Combiners electronically connect up to three battery banks to any charging source. After charging is complete, and the voltage drops to a preset voltage, the combiner disconnects the banks from each other. Basically, a combiner comprises two or more solenoid-operated relays with a sophisticated electronic control regulator, which makes it more than just an isolator.

  The advantage of this system is that you can adjust the combiner so the turn-on and turn-off voltages are appropriate for charging either AGM, gel-cell, or wet-cell batteries. Additionally, you can use a combiner with any charging source: alternators, solar panels, shore-power chargers, and wind generators, or in combination. This makes them very useful for controlling charging systems on both motorhomes and truck/trailers.

  CHAPTER 11

  Generators, Converters/

  Chargers, and Inverters

  In this chapter, we’ll cover three more charging technologies: generators, converters/chargers, and inverters. Each device can be purchased with or without chargers, although you should have at least one with charging capabilities, and each performs a different function for the RVer. A generator produces 120-volt AC power. A converter changes 120-volt AC power to 12-volt DC power. When boondocking, a converter/charger connected to a generator can charge your batteries. An inverter converts 12-volt DC power to 120-volt DC power, which is useful when boondocking and you want to run a 120-volt appliance.

  (RVIA)

  GENERATORS

  Generators are standard equipment in motorhomes, and are usually used for running the air conditioner while traveling. Although fuel prices can make it a more expensive option, a generator will get the job done. You can use your batteries at night and recharge them during the day with the generator, while also running an appliance or two. We do find it strange that not many motorhomers boondock since a generator makes a motorhome the best-equipped RV for boondocking and provides the easiest way to begin boondocking. But most boondockers tend to be trailerists, who must go to great lengths to equip their rigs for easy boondocking.

  Types of Generators

  RVers can use either a large, built-in generator called genset, or a smaller portable generator.

  Gensets

  Gensets are usually installed in motorhomes, although they can be mounted in storage lockers of large trailers. A genset is either hard-wired into the RV’s 120-volt AC system or accessed via an outlet where a shore-power cable can be plugged in. Most installations allow you to activate the genset by throwing a switch.

  With a genset, you can have access to a high-kilowatt output, which can range from 2. 5 to 17 kilowatts (2,500 watts to 17,000 watts). With this much power, you not only have all the advantages of a campground hookup, but also quite a bit of battery-charging capability if you have a good battery charger.

  Because they are built in, and powered by a combustion engine, gensets must have adequate ventilation and exhaust systems to prevent a buildup of fumes and carbon monoxide in the RV (see Chapter 6 for more on carbon monoxide).

  A genset is a very satisfactory way to charge your batteries when boondocking. While the batteries are charging, you also have current available for other purposes: cooking supper in the microwave, running the vacuum cleaner, answering e-mail, or cooling things down with the air conditioner. Also, charging with a genset is more efficient than running or driving your motorhome so the alternator can charge the batteries, and is more cost effective given the cost of fuel. When coupled with a multistage charger, a genset is as efficient at charging batteries as a high-output alternator with a multistage regulator.

  The genset should have enough capacity to run all the items you wish to run at the same time. Manufacturers will often install a genset large enough to run the air conditioner, but no additional items. Before buying an RV, to make sure the genset is large enough add up the wattage of all the
items you wish to run at one time; the wattage of the genset should be 20% larger than that amount.

  Recently a new genset called the JuiceBox came on the market for trailer use. Manufactured by Onan (www.onan.com), it is a standard genset of adequate size (4,000 watts, which is just enough to power an air conditioner) that is mounted on the back bumper of the trailer in its own box. This is a handy location because you don’t lose valuable locker space to the generator. The box is weatherproof and detachable, so you can remove it easily and set it up for use at the campsite or at home.

  Portable Generators

  Portable generators range in size from small 600-watt (0. 6 kW) units to not-so-portable 4,000- to 5,000-watt (4 kW to 5 kW) units. A small portable generator is very useful, especially if you are an RVer with a small rig. You can use them to run low-wattage televisions, VCRs, DVD players, satellite receivers, and computers, as well as other appliances, providing the generator can handle the load (see below). Unfortunately, most portable units are not large enough to run an air conditioner.

  For several years we used a 1,850-watt portable Coleman generator. It did a good job, but it could run only one appliance (such as a toaster or coffeemaker) at a time, and it was quite noisy.

  Portable generators have two wattage ratings for their output power, the surge rating and the constant or continuous rating. The surge rating refers to the amount of momentary power available for starting compressors and certain electrical motors. The constant wattage rating refers to the maximum power available for continuous operation of appliances and tools. This rating is the one to consider for battery charging and other appliances that will be used for any length of time.

  Selecting the Right Generator

  In Chapter 8, we outlined a process for determining daily power consumption. You can use this same process to ensure you don’t overload your generator, especially if it is on the small side. You want to be sure your wattage use doesn’t surpass your generator’s constant rating. For example, you cannot run a 1,200-watt hair dryer off a 600-watt generator or you would burn out the generator.

  Table 8-3 lists the amps and watts of different appliances and equipment. As you create your own table or list of devices you use in your RV to determine amp-hour use, also incorporate the watts you use. This way you have a handy reference to look at when you want to run several appliances at the same time off your generator. After awhile, you’ll learn what you can and can’t run at the same time, but in the beginning you may find this method helpful. This list will also help you choose a generator that will meet your needs. For battery charging, the generator should be 1,000 watts or larger.

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  Staying Safe: Generator Backfires

  If you plan to camp in USFS campgrounds and you buy a portable generator, make sure it has an exhaust manifold that has a backfire flame arrester to prevent starting a forest fire. Generators can backfire, which produces sparks, and the flame arrester will prevent this from happening. In fact, a flame arrester is a good idea for camping in any wilderness area, so make sure you buy a generator with a flame arrester.

  * * *

  Disadvantages

  Generators are useful to have around, but they do have some drawbacks. All generators produce noise, although some with better mufflers are quieter than others. Many campgrounds have strict rules regarding generator use for this reason. Some parks prohibit their use altogether, and others restrict the times they may be used. Most people hate the noise of one running in the next site, not to mention the smell of the exhaust fumes. So be sure to consider your neighbors in your use of a generator. No one likes to be in a wilderness area and have the wonderful sound of the wind and the birds ruined by the noise of a generator.

  Generators produce carbon monoxide. You should never go to sleep with a generator running. Fumes can enter the RV through windows or cracks. We covered carbon monoxide in Chapter 6, so refer back there for more information. With generators, however, you are not just endangering yourself. If you have neighbors camped close enough, they can be affected by carbon monoxide from your generator as well, particularly if they have their windows open.

  Small generators may also produce current with voltage spikes that can affect the operation of sophisticated electronic equipment, such as a multistage battery charger—the very item that can be most useful to boondockers. Most charger manufacturers recommend using a portable generator of at least 1,000 watts of continuous output for multistage charging. Most manufacturers of inverters with built-in battery chargers recommend using a 2,000-watt portable generator.

  CONVERTERS AND BATTERY CHARGERS

  A converter is basically a step-down transformer. It lowers 120 VAC to 12 VAC, then rectifies it to DC voltage using diodes in a rectifier circuit. If this sounds familiar, it’s because an alternator works in a similar way. In the early days of RVing, a converter was primarily used to provide 12-volt power to run the cabin lights when you were in a campground with an electrical hookup. This prevented the batteries from being discharged when a hookup was available. It did not charge the batteries; it was only an electrical substitute for battery usage.

  Eventually chargers were incorporated into these units, but they only had a small amperage output, 3 to 8 amps, and were used to keep the battery topped off at full charge. They didn’t have the ability to recharge a deeply discharged battery or battery bank. Some units were still basic converters, but by plugging in a Charge Wizard, an inexpensive adapter made by Progressive Dynamics, they could be converted into full-amperage chargers. These were good units, and we often wondered why RV manufacturers didn’t spend the extra $30 and install such devices at the factory.

  This is our old MagneTek converter mounted in our RV.

  Most good-quality RVs manufactured today come equipped with built-in converter/chargers that have outputs ranging from 30 to 75 or more amps and using either tapered or multistage charging.

  Types of Converters

  When shopping for a converter/charger, you’ll find a variety of types and options available—from basic to high tech. To give you an idea of the options, we’ll describe two high-tech converter/chargers and a basic, low-end converter. Later we’ll walk you through some tests we ran on two converter/chargers to give you an idea of performance and efficiency.

  The Inteli-Power 9160 A converter. To use it as a charger, you must plug in the Charge Wizard. (Progressive Dynamics)

  The DLS-55 from Iota Engineering (www.iotaengineering.com) has a rating of 55 amps and provides multistage charging with the IQ Smart Controller. The Smart Controller automatically controls the bulk, absorption, and float stages according to the battery’s capacity. It also monitors the battery at all times. Iota reports that its DLS converters produce exceptionally clean DC output, with little to no AC ripple (which can adversely affect AM radios, with effects ranging from static to failure).

  Progressive Dynamics (www.progressivedyn.com) produces a new series of converter/chargers that incorporates the Charge Wizard adapter mentioned earlier. The bottom right photo on page 117 shows the PD9260C converter/charger, rated at 60 amps. The built-in Charge Wizard provides automatic multistage charging.

  The Iota DLS-55 charger. (Iota Engineering)

  The Inteli-Power 9260 multistage charger. (Progressive Dynamics)

  In addition, both of the above models offer protection against low AC current, AC spikes, reverse polarity, and overheating.

  While we’ve made the case more than once regarding the efficiency and speed of multistage charging, it is especially useful if you use a generator to power your converter/charger. The faster your batteries charge, the less generator time you use, which translates into less fuel consumed and shorter periods of extra noise.

  Multistage chargers are available as stand-alone units as well as an option in many large inverters.

  If your charging needs are small, an unregulated converter/charger will be just fine. A Sears battery charger will provide tapered charging using constant amper
age, sometimes as low as 10 amps. Battery charging will be slow compared to multistage charging, but the job will get done. Remember, because this is an unregulated charger, you will have to constantly monitor the voltage to avoid overcharging. We tested a tapered converter/charger from Iota and have included the results below.

  One problem with the chargers of this type is that they usually operate at 14 volts or higher. At this voltage, 12-volt lightbulbs have a very short life, and other 12-volt appliances may also not be designed to operate on this high voltage. Many of the better-quality units have the capability to drop this high voltage to a float voltage of 13. 5 to 13. 7 volts after the batteries are fully charged, thus protecting the life of lightbulbs and other appliances. Sometimes these chargers are only set at a low charging voltage of 13. 8 volts or so to avoid this problem.

  Converter/Charger Tests

  We recently tested two converter/chargers: one was a good-quality tapered unit rated at 45 amps, and the other was a multistage unit rated at 40 amps.

  Test 1: Iota 45 Amp Tapered Charger

  The first test was with an older model Iota 45 amp charger powered through a campground outlet. We discharged our batteries over two evenings to −44. 7 amp-hours (25. 9% DOD). Here are the highlights from the test: