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Glossary of Power Terms

Absorption Charge
The second stage of three-stage battery charging. Voltage remains constant and current tapers as internal battery resistance increases during charging. This ensures complete charging.

Alternating Current (AC)
The type of electrical power supplied by the power utility. The unique characteristic of this form of electricity is that it reverses direction at regular intervals. For example, 120 Vac 60 Hz power reverses flow 60 times a second, hence the rating 60 Hz (cycles).

Ambient Temperature
Refers to the air temperature around the inverter and batteries, which will affect the output power of your system.

Amp/Ampere (A or I)
A measurement of the flow of electrical current. One amp is equal to the electric force of one volt acting across the resistance of one ohm.

Amp Hour (Ah)
One amp of electrical current flowing for one hour. Expresses the relationship between current (amps) and time. (Ohm's law: A = V/R)

Amp Hour Capacity
The ability of a fully charged battery to deliver a specified quantity of electricity (Amp-Hr., Ah) at a given rate (Amp, A) over a definite period of time (Hr.). The capacity of a battery depends upon a number of factors such as: active material, weight, density, adhesion to grid, number, design and dimensions of plates, plate spacing design of separators, specific gravity and quantity of available electrolyte, grid alloys, final limiting voltage, discharge rate, temperature, internal and external resistance, age and life of the battery (or battery bank).

The current-carrying capacity of an electrical conductor or device, expressed in amperes.

AGM (Absorbed Glass Mat) Battery
A lead acid, maintenance-free battery.

A group of solar electric modules wired together.

AWG (American Wire Gauge)
A standard used to measure the size of wire.


Battery Charger
A device that is used to replenish the capacity of a battery (its ?charge?) by supplying DC current to the battery.

Bulk Charge
The first stage of three-stage battery charging. Current is sent to batteries at the maximum rate they will accept while voltage rises to full charge level.


An electric circuit is the path of an electric current. A closed circuit has a complete path. An open circuit has a broken or disconnected path.

Circuit (Series)
A circuit which has only one path for the current to flow. Batteries arranged in the series are connected with the negative of the first to the positive of the second, negative of the second to the positive of the third, etc. If two 6-volt batteries of 50 amp-hours capacity are connected in series, the circuit voltage is equal to the sum of the two battery voltages, or 12 volts, and the amp-hour capacity of the combination is 50 amp hours.

Circuit (Parallel)
A circuit which provides more than one path for current flow. A parallel arrangement of batteries (of like voltage and capacity) would have all positive terminals connected to a conductor and all negative terminals connected to another conductor. If two 12-volt batteries of 50 amp-hour capacity each are connected in parallel, the circuit voltage is 12 volts, and the amp-hour capacity of the combination is 100 amp hours.

The rate of flow of electrical charge. The flow of current is measured in amps.

In a battery, one discharge plus one recharge equals one cycle.


Deep Cycle
A deep cycle occurs when a battery is discharged to 50% of its capacity (50% depth of discharge). A deep-cycle battery is one that is intended to be deeply discharged and charged repeatedly.

Depth of Discharge (DOD)
The amount of energy or charge removed from the battery bank, usually expressed as a percentage. A depth of discharge of 0% indicates a fully-charged battery, and a depth of discharge of 100% indicates a fully-discharged battery.

Direct Current (DC)
The type of electricity stored in batteries and generated by solar electric devices. Current flows in a single direction.

When a function is disabled, it is not allowed to occur and if it is occurring, it is terminated. Regardless of other conditions, the function will not be activated. For example, even if AC power is present, if the charger is disabled, the unit will not charge. The charger must be enabled. See ?Enable? in the glossary.

Stored energy being released from a battery.

DC Loads
These loads are those that run off a DC electrical system (battery). A few examples of DC loads are pumps, lights, fans, power vents, toilet, inverters, and some water heaters. DC loads rely on the batteries for power.


Echo Charger
Auxiliary charger that can charge your engine battery when the main charger is in
Bulk or Absorption mode and the house battery voltage is at 13.2 volts DC or higher.

A conductive medium in which the flow of electricity takes place; this is the liquid found inside storage batteries.

When a function is enabled, it is allowed to occur but other conditions may have to be met before the function is activated or turned on. For example, the charger function on the MS2000 may be enabled, but it will not charge unless qualified AC power is present.

Engine Battery
A battery that is separate from the House battery, specifically designated to provide power for engine starting. In a system with a house battery and an engine battery, the inverter would not have its main power cables connected to the engine battery.

Equalization or Equalize Charge
A deliberate, controlled overcharge of the batteries which brings all cells up to the same voltage potential, reduces sulfation and stratification in flooded (or wet) lead-acid batteries. Not necessary and harmful on Gel or sealed batteries.


Float Charge
The third stage of three-stage battery charging. After batteries reach full charge, the charging voltage is reduced to a lower level to reduce gassing (boiling of electrolyte) and prolong battery life. This is often referred to as a maintenance charge, since rather than charging a battery it keeps an already-charged battery from self-discharging.


Gel Cell Battery
A type of battery that uses a gelled electrolyte solution. These batteries are sealed and are virtually maintenance free. Not all sealed batteries are the gel cell type.

When used in reference to utility power, it refers to a system of electrical transmission and distribution lines.

Grid Tie
An electrical system that is connected to a utility distribution grid. For example, Xantrex SW line tie inverters are designed to connect to and interact with utility power.

The reference potential of a circuit. In automotive use, the result of attaching one battery cable to the body or frame which is used as a path for completing a circuit in lieu of a direct wire from a component. This method is not suitable for connecting the negative cable of the inverter to ground. Instead, route the cable directly to the negative terminal of the battery.

Ground Fault Circuit Interrupter (GFCI)
A protective device that rapidly de-energizes a circuit when current to ground exceeds a predetermined value.

Ground Fault Protection (GFP)
A circuit protection device that prevents the flow of electrical current to earth if a short circuit is present. Usually required in wet locations, for example, for outdoor, kitchen, and bathroom circuits.


Hertz (Hz)
The frequency, or number of times per second, that the flow of AC electricity reverses itself. Also referred to as cycles (see "alternating current").

High Battery Protection
A control circuit that disconnects charge current flowing to batteries when voltage reaches a dangerously high threshold. Prevents damage created by excess gassing (or boiling) of electrolyte.

House Battery
The house battery is the large capacity, deep cycle battery that is connected to the inverter/charger's main DC terminals.

Hybrid Systems
These are systems that combine two or more renewable energy technologies. A combination photovoltaic and wind system, or a photovoltaic system that recovers and utilizes heat from the panels for space or water heating are hybrid system examples.

A simple device that measures the specific gravity of battery electrolyte. Specific gravity readings express state of charge/discharge of battery.


Idle Current
The amount of electrical power required to keep an inverter ready to produce electricity on demand.

Inductive Loads
TVs, VCRs, stereos, computers, and electric motors (power tools, vacuum cleaners, for example) are examples of inductive loads which surge on start up. They require a high start-up current compared to a resistive load such as a toaster or a coffee pot.

Inrush Current
The peak power that a load will draw at the instant that it starts up.

A device that converts DC power to AC power.


Kilowatt (kW)
One thousand watts of electricity. Ten 100-watt light bulbs use one Kilowatt of electrical power.

Kilowatt hour (kW/h)
One kW of electrical power used for one hour. The most common measurement of electrical consumption, most grid connected electrical meters measure kWh for billing purposes.


Light Emitting Diode (LED)
A device used to display various status functions.

Line Loss
A voltage drop caused by resistance in wire during transmission of electrical power over distance. Line loss is why you must increase the size of DC battery cables the further the inverter is from the battery or battery banks.

Line Tie
An electrical system that is connected to a utility distribution grid. For example, Conext CL line tie inverters are designed to connect to and interact with utility power.

Any device that consumes electricity in order to operate. Appliances, tools, and lights are examples of electrical loads.

Low Battery Protection
A control circuit that stops the flow of electricity from batteries to loads when battery voltage drops to low levels. This prevents over-discharge of the batteries.


Main Charger
The main charger output is at the main DC terminals on the inverter/charger and connects to the house batteries. The main charger replenishes the charge to the house batteries. The main charger can be configured as a two stage or a three-stage charger.

Maximum Power Point Tracking (MPPT)
Every PV (solar electric) device has a point where maximum current is delivered. MPPT electronically adjusts the output of a PV device to the maximum power point.

Modified Sine Wave (MSW)
An AC wave form (generated by many inverters) that is a pulse width modified square wave.


National Electric Code (NEC)
The electrical wiring and installation standards used in the United States.

Designating or pertaining to electrical potential. The negative terminal is the point from which electrons flow during discharge.


Off Grid
An electrical system that is not connected to a utility distribution grid.

A unit for measuring electrical resistance.

Ohm's Law
Expresses the relationship between voltage (V) and current (I) in an electrical circuit with resistance (R). It can be expressed as follows: V=IR. If any two of the three values are known, the third value can be calculated by using the above formula.

A device that displays the wave form created by an electrical generating device such as a generator, inverter, or utility.

Overload/Overcurrent Protection
A control circuit designed to protect an inverter or similar device from loads exceeding its output capacity. (A fuse, for example, is an overcurrent protection device.) All Xantrex inverters have internal circuitry to protect themselves from most overload/overcurrent conditions.


Parallel Wiring
A group of electrical devices, such as batteries or PV modules, wired together to increase ampacity, while voltage remains constant. Two 100 amp hour 12 VDC batteries wired in parallel will form a 200 amp-hour 12 VDC battery bank.

Photovoltaic (PV) Panels
These are the devices that convert sunlight into electricity.

Photovoltaic (PV) System
The components that form a solar electric generating system, usually consisting of PV modules, charge controller, circuit protectors (fuses or breakers) and batteries.

A battery is made up of lead plates separated by an electrolyte solution. The electrolyte solution chemically reacting with the lead plates causes the flow of electrons known as electric current.

Designating or pertaining to electrical potential; opposite of negative. The positive battery terminal is the point where electrons return to the battery during discharge.

Power Factor
Power factor is the ratio between true power (Watts) and apparent power (Volt Amps)

Power Sharing
The feature of the charger to reduce its output when the AC power being consumed by the charger and external AC loads connected to the output of the inverter are in excess of the input breaker rating.


Resistive Loads
Toasters, coffee pots, and incandescent lights are examples of resistive loads. They use a resistive heater element to generate heat or light.

S Jump to Top

Series Wiring
A group of electrical devices, such as batteries or PV modules, wired together to increase voltage, while ampacity remains constant. Two 100 amp hour 12 Vdc batteries wired in series form a 100 amp hour 24 Vdc battery bank.

Sine Wave
The optimal output wave form of alternating current (AC). A smooth wave going above and below zero.

As a battery discharges, its plates become covered with lead sulfate. With regular recharging, the lead sulfate leaves the plates and recombines with the electrolyte. If the lead sulfate remains on the plates for an extended period of time (over two months), it hardens, and recharging does not remove it. Sulfation reduces the effective plate area and the battery's capacity. Equalization of flooded (or wet) batteries helps to reduce sulfation.

Surge Capacity
The amount of current an inverter can deliver for short periods of time. Most electric motors draw up to three times their rated current when starting. An inverter will 'surge? to meet these motor-starting requirements. Schneider Electric inverters have surge capacities at least twice their continuous ratings, and many surge to three times their continuous ratings.

Over time, electrolyte tends to separate. The electrolyte at the top of the battery becomes watery while it becomes more acidic at the bottom. This effect is corrosive to the plates. Equalization of flooded (or wet) batteries helps reduce stratification.


Temperature Compensation
Optimal battery charging voltage is dependent on the battery temperature. As the ambient temperature falls, the proper voltage for each charge stage needs to be increased. When the ambient temperature increases, the proper voltage for each charge stage needs to be decreased. On some products, the Battery Temperature Sensor (BTS) allows the charger or inverter/charger to automatically scale charge-voltage settings to compensate for ambient temperatures. On others, there is a setting for hot, cold, and warm settings.

Transfer Switch
A switch designed to transfer electricity being supplied to loads (appliances, for example) from one source of power to another. A transfer switch may be used to designate whether power to a distribution panel will come from a generator or inverter.

Trickle Charge
Trickle charging, also called float charging, means charging a battery at the same rate as the rate of self-discharge. All batteries self discharge over time.

TSC (Temperature Sensitive Charging)
The ability of the charger to adjust its charging voltage based on the temperature sensed at the battery bank if a temperature probe is used.


Volts (V)
A unit of measure of the pressure in an electrical circuit. Volts are a measure of electric potential. Voltage is often explained using a liquid analogy, comparing water pressure to voltage: a high pressure hose would be considered high voltage, while a slow-moving stream could be compared to low voltage.

Volt-amps (VA)
A measure of the apparent power equivalent to the true power (watts) in resistive loads, but exceeding watts in non-resistive loads. VA is calculated by multiplying volts times amps without using power factor.


Watt(s) (W)
A quantitative measurement of electrical power taking into account power factor. Watts are calculated by multiplying volts times amps times power factor. (watts = volts × amps × power factor)

Watt Hour (W/h)
Electrical power measured in terms of time. One watt hour of electricity is equal to one watt of power being consumed for one hour. A one-watt light operated for one hour would consume one watt hour of electricity.

Wet Cell Battery
A type of battery that uses liquid as an electrolyte. The wet cell battery requires periodic maintenance: cleaning the connections, checking the electrolyte level and performing an equalization cycle.

Wind Energy Conversion System
Usually known as a windmill or a wind turbine. WECS convert energy from the wind into electricity. A complete set of components may include the following components: Wind Turbine, wiring, inverter, controller, batteries and other components depending upon the sophistication of the system.


Xanbus is a network communications protocol, developed by Schneider Electric.
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