GLOSSARY
This is a short list of terms you'll find when working with energy systems. This is by no means a comprehensive list, but covers the main terms you'll find on our site as well as those of our partners.
Alternating Current (AC)
A method of power transmission where the current changes directions periodically, as opposed to direct current (DC). AC is used for long-distance power transmission over power lines, as well as for home electrical devices such as refrigerators, stoves, and dryers.
​
Amp (A)
The standard unit of electrical current in a circuit.
​
Amp-Hour (Ah)
A unit of stored electrical capacity, or the amount of current a battery is capable of producing over a period of time. 1 Ah equals a current of 1A flowing for one hour. Assuming ideal conditions, a 150Ah battery is capable of supplying 150A for one hour, or 75A for two hours.
​
Battery Charger
A device that directs current into a rechargeable battery. These devices typically monitor current and voltage and adjust their output accordingly for optimum battery health.
​
Battery Management System (BMS)
An electrical system built into components such as inverters and smart control batteries that automatically manages battery health, monitoring charge levels and input currents to maximize battery lifespan. BMS also protects against overcharging and over-discharging.​
​
Current
The amount of charge flowing through a circuit. Measured in amps (A).
​
DC to DC Charger
A device that is capable of taking direct current (DC) from a device like a tow vehicle's alternator and using it to charge a house battery. These devices typically automatically regulate voltage to ensure optimum battery health. ​​
​​
Depth of Discharge (DoD)
The percentage of a battery's capacity that can be drained before it requires recharging. Generally used in relation to the rating of a battery. A 100Ah battery with 90% DoD will allow 90Ah of discharge before the internal BMS will not allow any more discharging to protect the battery.
​
(Note: DoD is occasionally used as the inverse to state of charge, (SoC), which refers to the amount of energy a battery is capable of producing at a given moment. For example, with this usage, a battery with 20% DoD has 80% SoC, or power remaining. When you see DoD in a Future Solutions context, we are referring to the first definition: total discharge capability.)
​
Direct Current (DC)
A method of power transmission where the current's direction remains the same, as opposed to alternating current (AC). DC is used in low-voltage systems, electronic devices like laptops and other smart devices, and is output by batteries, solar panels, and alternators. Household appliances typically take AC, and thus an inverter must convert the DC to AC before used for these devices.
​
Inverter
A device that converts DC, such as from a battery, solar panel or alternator, to AC for use in coach circuits.
​
Inverter/Charger
A device that combines the functions of an inverter and a battery charger. They are capable of receiving DC from a device like a solar panel and converting it to AC for use in coach circuits, as well as directing the DC to the batteries to charge the home bank. These devices can also take AC input (shore power or generator) and direct it to charge a house battery bank while inverting DC to AC simultaneously.
​
Maximum Power Point Tracking (MPPT)
A technique used to maximize the charge output from a solar array. A solar cell's efficiency changes depending on a number of factors, such as temperature, amount of sunlight, and the load. An MPPT-enabled solar charge controller is able to monitor these factors and automatically adjust the load characteristic for optimal charging in any environment.
​
Multiplexing
In an RV context, multiplexing refers to centralized control and monitoring of multiple electrical systems through a single interface. It simplifies control of a solar system by running all communication channels to a central hub, then allowing that hub to communicate with the user via a smart device app or external display, such as the Victron GX Touch 50.
​
Power
A measure of actual energy used by a device. Measured in watts (W) and calculated by multiplying voltage and amps.
(W = V x A.) ​A 10A device pulling from a 120V outlet will use 1200W.
​
Shunt
A device that monitors the current and voltage of your battery bank. This allows it to give real-time updates on state of charge (SoC), time remaining in the bank given the current load, as well as real-time amperage and voltage. Shunts usually relay this information to a display via a cat5 cable, but certain shunts, such as the Victron SmartShunt, use built-in Bluetooth capabilities to communicate with an app on a smart device.
​
Solar Charge Controller
A device that monitors the current coming from a solar array and automatically adjusts the current for optimal charging. A charge controller ensures that your battery bank charges in the shortest time possible while maintaining optimum battery health in all conditions.
​
State of Charge (SoC)
A measure of the amount of energy remaining in a battery at a given time. A battery with 30% SoC has used 70% of its usable capacity. A shunt is able to calculate SoC and relay that information to a display or smart device app.
​
Volts (V)
A measure of electrical potential. Used in combination with current, measured in amps, to determine overall power usage, measured in watts. (W = V x A.) A 10A device pulling from a 120V outlet will draw 1200W.
​
Watts (W)
A measure of power, or actual energy used by a device. Wattage is calculated by multiplying voltage by amperage.
​
Watt-Hours (Wh)
A measure of power over time, used for calculating energy usage. A 10A device pulling from a 120V outlet for 1 hour will draw 1200Wh, or 1.2 kilowatt-hours (kWh).​​
COMMON QUESTIONS
What is the difference between amps (A) and amp-hours (Ah)?
Amps are a measure of current at a given moment, with no relation to duration of time. A device drawing 20A tells you only that, at the time of measuring, the device is pulling 20A.
​
Amp-hours are a measure of electrical capacity over time, typically used for measuring batteries. Assuming ideal conditions, a 12V 100Ah battery is capable of supplying 100A for one hour, 10A for 10 hours, or 1A for 100 hours.
​
What is the difference between watts (W) and watt-hours (Wh)?
Watts are a measure of power at a given moment, with no relation to duration of time. Watts are calculated by multiplying voltage by amperage. A device drawing 20A from a 120V outlet tells you only that, at the time of measuring, the device is using 2400W of power, or 2.4 kW. (20A x 120V = 2400W)
​
Watt-hours are a measure of power usage over time, typically used for calculating energy bills. A 20A device pulling from a 120V outlet for 1 hour uses 2400Wh, or 2.4 kWh. (20A x 120V x 1h = 2400Wh)
​
What is the difference between direct current (DC) and alternating current (AC)?
Both are methods of transferring power over distances. AC alternates direction periodically, making it easy to transform to high voltages for efficient long-distance transmission to minimize energy loss. This is why power grids use AC.​ Since the power grid provides AC by default, many household appliances like refrigerators, dryers, and coffee makers are designed to use AC. This allows them to simply plug into your home circuits with no need to convert to DC.
​
DC flows in only one direction, and is generally used at lower voltages than AC. DC is output from devices like batteries, solar panels, and alternators. In addition, certain electronic devices like computers and smart devices use DC internally, and thus include an AC-DC adapter. DC from a solar array must be converted to AC for use in coach circuits with household appliances. This is done by an inverter.