There are two fundamental methods of Sump Battery Backup.

The first involves the introduction of a secondary battery backup pump as a redundant system to assist the main basement sump pump.  This system uses the conventional method of a battery backup for sump and has been used for decades. It consists of an auxiliary or secondary pump, driven by a DC motor accompanied by a package consisting of a battery and charger. The pump is installed in the sump pit alongside the main sump pump. The auxiliary pump is fitted with a float sensor which is mounted at a level above that of the main pump float sensor. The intention behind the scheme is that the secondary sump pump should activate in the event that the main pump allows the water level to arrive at the level of the secondary pump float.  In such a system, only the secondary pump remains functional in the event of electricity failure.

Among the advantages of battery backup for sump pumps of this type is that there is pump redundancy. The disadvantage of such battery backup pumps is that the redundant secondary pump is incapable of handling the same water volume as the main pump. During torrential downpours, the consequences of this kind of situation can be a basement flood when electricity becomes absent.  Also the sump pump backup battery supplied with the system is usually small resulting in limited backup time.

The second approach to a sump pump with battery backup is based on a completely different assumption and it is this: Most basement flooding occurrences are not caused by the main pump itself suffering mechanical failure, but rather by the loss of electricity. Ironically, this usually happens during a thunderstorm when the pump’s capacity is most needed. With this method, when grid power becomes absent, electricity to the main pump is maintained, allowing the main pump to keep operating. As with the first type of system, there are pros and cons to a battery backup for existing sump pump.

The main advantage of this sump pump battery backup  which powers an existing main pump, is that it  enables the pump to function at full capacity during a power outage. Its quick installation does not involve cluttering the sump pit. Because it does not need to be close to the main pump, together with its battery, it can be mounted in a place remote from the sump pit.

The main disadvantage is that there is no pump redundancy. Both types of system are available in the market. Ultimately it is the consumer who decides which is the best battery back up.

The distinction between “power converters” and “power transformers” begins with an understanding of the two basic forms of electricity transmission. They are commonly referred to as AC and DC systems. AC is the abbreviation for “alternating current”. AC operating at 60 Hz. describes an electrical current shifting direction, to and fro, in a circuit 60 times per second. Alternating current is the electrical format typically available in most buildings from electrical utility sockets on the power grid. (120 Volts AC in North America)

What is DC power? DC is the abbreviation for “direct current”, current constantly flowing in the same direction. One of the most commonly recognizable sources of DC power is the battery.

There are some very strong practical and economic reasons, which have decided where each of these forms of power are used today:

When power companies generate electricity at macro power generation sites such as dams, their ultimate objective is to distribute energy to home and industry. In order to achieve this, power must be delivered through major power lines. Minimizing the energy lost in this process requires that these lines be operated at very high voltages. Otherwise, the physics of the situation would dictate that the size of the conductors that would be needed to carry this energy would become extremely large, heavy, expensive and physically unmanageable. High voltage lines minimize energy losses along thousands of miles distance. The intention behind the design of such power transmission lines is, that at various points along its path, power can be branched and tapped at distribution stations. There the voltage level of the main power line is adapted (transformed) to suit the consumption levels of local customers. An analogy would be a large water pipeline of huge diameter designed to deliver millions of gallons to a region. Along the way, consumers of this water tap the pipeline with much smaller diameter pipes suitable to accommodate the level of their respective consumption. This tapping becomes analogous when it comes to electricity.

This is where the electrical transformer plays a role. A transformer is an electric component used to change the value of a voltage from one level to another. It is a simple unitized electrical element, whose construction involves an iron or ferrite core and groups of copper conductors, referred to as windings, which are wound around this core. A transformer may be referred to as a “step up” or “step down” type depending on its use i.e. whether to increase or decrease voltage. The laws of physics dictate that a transformer behaves in this capacity only with respect to AC voltage. This is why it is more completely referred to as an AC transformer. The AC transformer is the fundamental component, known to engineers, for voltage changing. And when a transformer’s function is referred to in an electrical sense as transforming, what is exclusively meant is, that it changes AC voltage to AC voltage. Because this fact is taken for granted in the electrical trades, often the prefix AC is dropped and it is simply referred to as a transformer. It is the only electrical component capable of efficiently performing voltage changing on a solo basis, without the necessity of including additional electrical components. This is the major reason why the AC method was selected for power generation and transmission early in power grid evolution.

What can be the derivation of the term “DC-DC transformer”? DC to DC transformer represents a definition of a functional requirement rather than an accurate technical description. Due to the fact that DC voltage cannot be fed into a transformer constructed as above described, the term DC-DC transformer is a misnomer. Similarly, “DC transformer” also a technically incorrect term. Use of the term “DC-DC transformer” suggests a desired invocation of the function of DC-DC converters. “DC-DC converter” is an electrically accurate term to describe devices used to change DC from one level to another. Another proper term is DC DC power supply.

Today there are many good reasons for converting DC to DC. Industrial computers and electronics are used to control a myriad of processes involved in industry and daily living. The energy for operating electronic devices is invariably in DC form. The nature of a given electronic circuit determines the voltage level needed for its operation. When an environment where such a circuit is intended for installation does not make available the matching voltage, DC-DC conversion becomes necessary.

Example 1: A process control computer used to spray paint and functions at 24V. It is needed for installation in a truck with a 12V system. The installation of a DC-DC step up converter (from 12V to 24V) would enable the 24V device to be used on such a truck.

Example 2: A mobile radio transceiver designed to operate with a 12V input. It is installed on a forklift which has a 36V system. A step down DC-DC converter (from 36V to 12V) would be an appropriate interface.

What is the circuit topology of DC-DC conversion? Typically a converter DC DC, uses the DC voltage available for input and chops it into AC. This AC is then applied to the converter’s internal transformer which changes the AC into a different level. This new AC level is then converted back to a new DC level. The circuit which accomplishes the entire conversion typically consists of several circuit elements, only one of which is an AC transformer. Among the characteristics that specify DC-DC converters are input/output voltages, ability to regulate voltage, physical size and power handling capability. Another important property of DC-DC converters is isolation. An isolated DC converter has its input and output voltages disconnected from one another. In some applications dealing with high voltages, this property is crucial.

As we mentioned in Part 1 of this series, North American commercial vehicles’ electrical systems are different from those used in Europe and by the NATO military. Variations in voltages and connectors require the use of electrical trailer interfaces. Part 1 focused on power resistor voltage dividers. In this section we’ll go over another electrical trailer interface — centralized power switching regulators, otherwise known as centralized DC-DC converters — including this interface’s advantages and disadvantages.

How the Centralized (Bulk Power) Method Works

Bulk power is imported from the tractor through two cables to a 24V-to-12V DC-DC converter mounted on the trailer. The cables that carry this bulk power must be of sufficient diameter to handle the trailer’s total electrical demand without overheating. The DC-DC converter should efficiently change 24V to 12V DC. Signals are applied from the tractor electrical output connector pins to a relay network which is housed adjacent to the DC-DC converter. These signals energize the relays in the network such that the tractor signals (24 VDC) are translated into corresponding signals of voltage taken from the DC-DC converter output (12 VDC). These signal voltages are applied to the appropriate pins of the trailer input connector.

This interface method has two significant advantages over the resistor divider method (discussed in Part 1 of this blog). First, the transformation of power from 24V DC to 12 DC is efficient — usually approximately 90%. This implies that dissipative losses in the order of 100 watts would occur in the DC-DC converter. This condition is manageable from a heat evacuation standpoint. Second, this configuration offers excellent regulation because the DC-DC converter’s 12V DC output fluctuates marginally as load is varied.

However, centralized power switching regulators have disadvantages relative to other electrical trailer interfaces. First, towing a military tractor would require the addition of connectors and wire harnessing to enable the delivery of the trailer’s entire electrical demands through the two wire conductors carrying the bulk input power. Second, should the centralized switching regulator fail to function, the entire trailer may lose power. Third, a heavy circuit breaker must be installed at the power source for short-circuit protection. Fourth, the physics of such a large switching regulator (DC-DC converter) requires that some of its magnetic components be relatively large. This makes them vulnerable in conditions of shock and vibration. Finally, this approach does not necessarily allow for the conveyance of multiplexed signals such as PLC4 between tractor and trailer along designated circuit lines — a significant disadvantage in the context of 21st century commercial vehicle design. When it comes to ABS brake operation, PLC4 tractor-trailer signal transmission is critical for regulatory compliance. This aspect will be discussed in a later blog post.

In the third part of this blog series we’ll go over a third type of electrical trailer interface. This type is called distributed power switching regulators. This type of electrical trailer interface is the kind used in our trailer interface models.

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This offer is available while quantities last until March 31, 2012.

Now that we’re in the chilly season, it’s a great time for dealers in wood pellet stove dealers and other alternative fuel devices to consider our emergency power battery back-ups.  SEC America’s Surefire SentryTM automatic battery backup systems can silently and efficiently maintain the operation of wood pellet stoves or heating appliances when power fails.

How Our Emergency Power Battery Back-Ups Work

All Surefire Sentry automatic battery back-up systems work in the following way: When utility power fails, the system instantly draws energy from a battery to enable continued heating appliance operation. When utility power returns, the back-up system automatically switches the appliance back to AC wall outlet power. At the same time, the battery charger in the backup system resumes charging the battery to return it to full capacity in preparation for the next power failure. This sequence is fully automatic and designed to occur unattended, and is effective whether the user is at home or not providing peace of mind.

Reliable and Easy-To-Use Power Back-Up Solutions

The Battery Back-Up systems are easy to set up. They plug into standard wall outlets without additional of special wiring. The user is required to supply only a deep cycle battery. No maintenance is required, and there is no fuel or moving parts about which to worry. All models come with a detailed instruction manual and are backed by a one-year factory warranty.

Fuel Stove Power Automatic Back-Up Solutions for Rural Areas

If you live in a rural area that may be vulnerable to extended outages, SEC Battery Back-ups can be made to operate up to 24 hours with the use of an expanded battery bank.  In comparison, a single 100 A-hr battery affords only 8 hours of operation in the case of a wood pellet stove whereas gas heaters and Toyo kerosene heaters will last up to 19 hours on a single battery. The back up time for a given appliance operating from a given sized battery bank can be determined by applying the formula in the SEC application note Calculating Battery Back Up Time.

Model Offering

SEC alternative fuel battery back-up models may be used for a wide variety of alternative fuel appliances including, wood pellets stoves, corn stoves, kerosene heaters, gas heaters, coal stoves and small water circulation pumps. Available models are SF512, SF503A, SF707 and SF709, each having a different level of maximum output, the SF 709 having the highest at 1000 Watts. Models SF512 and SF 503A produce modified sine wave power when operating in the standby mode making them a cost effective solution for backing up older stove models. Most newer micro processor controlled pellet stoves require sine wave power and it must be supplied in standby mode. Models SF 707 and SF 709 provide true sine wave power at all times making them suitable for microprocessor controlled appliances. Prior to purchasing a battery back up the user should consult his heating appliance owner’s manual, or its manufacturer to determine the maximum power consumption and to determine whether the pellet stove is microprocessor controlled.  This should be the approach whether the heating appliance is a wood pellet, corn pellet stove, kerosene heater or coal stoker.

Contact SEC America for more information.

Additional Links

Surefire Sentry brochure

North American commercial vehicles have electrical systems unlike those of Europe and the NATO military. Specifically, they operate at different voltages and use dissimilar connectors. As examples of wiring conventions, North American commercial vehicles use a 7 Pin SAE 560 system and NATO vehicles use a 12 pin system conforming to the STANAG 4007 standard. The European configuration is similar to the North American 12 V based SAE 560 system except that they are 24V based and use either a single ISO 1185 connector or one in combination an ISO 3731 connector . In addition to cross coupling vehicles from these three jurisdictions, when vehicles wired to RV standards become possible mating options to them the interfacing possibilities are further multiplied. Only electrical trailer interfaces make possible the electrical coupling of two vehicles wired with unrelated standards. To date, truck-trailer interfacing has been achieved with one of three commonly used electrical circuits: power resistor voltage dividers, centralized power switching regulators and distributed switching regulators. This three-part blog series will describe these circuit configurations, mentioning the pros and cons of each approach in the context of the electrical trailer interface application.

Functions of Trailer Electrical Interfaces

Electrical trailer interfaces have two functions. The first is to ensure that a signal at any given pin combination of the tractor is translated into an equivalent functional signal at the proper pins of the trailer connector. The second is to convert the voltage level of a power signal or combination of signals at the tractor output connector to a power signal of acceptable voltage at the intended pin of the trailer connector.

Power Resistor Voltage Dividers: How They Work

Power resistor voltage dividers work by dropping voltage through fixed power resistors. This method has three primary advantages relative to other electrical trailer interfaces:

• It is the least expensive.
• It has a simple circuit with a low component count.
• If the output of one pin should fail, the others remain unaffected.

On the other hand, power resistor dividers have several disadvantages:

• This approach is 50% efficient at best: For every watt of power transformed, at least one watt is dissipated as heat. As the source for the dissipated power, the tractor’s electrical system has to be able to furnish this power.
• The housing to contain the power resistors has to be of large enough volume to enable internal components to remain within their operating temperature limits.
• Power resistors of high dissipation capacities are also large and do not withstand shock and vibration as well as small components. Because of their high hot-spot temperatures, they are inherently unreliable.
• Because the voltage drop across the resistor depends on the load current, this method has very poor regulation and can lead to sequential component failures.
• Poor voltage regulation limits the number and characteristics of accessories that may be loaded on the auxiliary pin.
• This method cannot be used for stepping up voltage, as in the case of a 12V towing vehicle and 24V trailer.

Part 2 of this blog series will focus on the advantages and disadvantages of another electrical trailer interface: centralized power switching regulators; then in Part 3 we’ll move on to the type used in SEC’s trailer interface models: distributed power switching regulators.

Links to Additional Information

http://www.tradoc.mil.al/Standartizimi/Downloads/4007Eed02.pdf

SEC’s Electrical Conversion Products

SEC America, LLC introduces Model 6948 capable of 25A of continuous output ideal for facilitating the transfer of Fuel Cells.  Fuel cells require a reliable source of power to ensure that no degradation in its energy conversion takes place during transportation. The converter must be reliable in order to avoid any power interruption which would require restarting the power generation process. Model 6948 is an internally encapsulated and rugged DC-DC converter designed to withstand shock, vibration, and temperature excursions from -40C to +60C.
Additional electrical features include optional remote or local activation.

The UTC 2412RV has, at its input, a NATO (12 pin connector) and an RV (7 blade connector) at its output enabling a rapid interconnection of military and civilian vehicles without hard wiring. The interface also transforms the 24V input from the military towing vehicle to the 12V necessary to operate a civilian trailer while at the same time allocating voltages to corresponding pins. When implementing the UTC 2412RV with trailers that have electric brakes, the user must ensure that the trailer is equipped with a suitable brake actuator.

UTC 2412RV may be mounted to either trailer or towing vehicle.

Model 362 is a compact and mechanically rugged DC-DC Converter which has been field proven in thousands of military tanker trailers. Other common applications include use in fork lift trucks and industrial process control. Weighing only 5 pounds in a volume of approximately 1/20 of a cubic foot Model 362 has an MTBF of 60,000 hours at 80% of maximum rating.