Users Guide to off Grid Energy Solutions

Voltage Converters and Power Conditioning Units Fact Sheet:

Voltage Converters. If an appliance operates at a different voltage than the battery (i.e. if a radio draws 6 volts dc when the storage battery is at 12 volts dc), then a voltage converter is required to step the current down to the proper voltage. This will avoid damage to the radio (or other appliance). Voltage converters are often available in electric appliance stores.

Inverters. Especially with large systems, it may be necessary to run appliances that require 240 VAC (i.e. colour televisions, refrigerators or videos). Inverters convert dc power into a form suitable for high voltage AC loads. Changing dc power into AC power is also called inverting dc to AC, which is why low voltage lamp ballast are called inverters. Unlike ballast inverters in lamps (which change up to 50 watts of dc power to AC), invert hundreds or thousands of watts from dc to AC.

In the process of converting dc to AC inverters use up energy. They are typically about 85% (or less) efficient in converting power. When planning large systems the energy loss in conversion must be included in calculations.

If power conditioning units are used in a system, they must be properly sized to handle the highest current possible, or the peak energy demand i.e. when all the appliances are turned ON).

Terms and definitions

Alternating current (AC): electric current in which the direction of flow changes at frequent, regular intervals

Charge controller: a device which protects the battery, load and array from voltage fluctuations, alerts the users to system problems and performs other management functions

Charge regulator: see charge controller.

Ccircuit: a system of conductors (i.e. wires and appliances) capable of providing a closed path for electric current

Converter: An electronic device for DC power that steps up voltage and steps down current proportionally (or vice-versa). Electrical analogy applied to AC: See transformer.

Mechanical analogy: gears or belt drive.

DC - Direct Current: DC is the type of power produced by photovoltaic panels and by storage batteries. The current flows in one direction and polarity is fixed, defined as positive (+) and negative (-). Nominal system voltage may be anywhere from 12 to 180V. See voltage, nominal.

Efficiency: Efficiency is the percentage of power that gets converted to useful work. Example: An electric pump that is 60% efficient converts 60% of the input energy into work - pumping water. The remaining 40% becomes waste heat.

Inverter: An electronic device that converts low voltage DC to high voltage AC power. In solar-electric systems, an inverter may take the 12, 24, or 48 volts DC and convert it to 115 or 230 volts AC, conventional household power.

Transformer: An electrical device that steps up voltage and steps down current proportionally (or vice-versa). Transformers work with AC only. For DC, see converter.

Mechanical analogy: gears or belt drive.

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