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NRGVault products beneath an AC current and DC current title

AC/DC – Alternating and Direct Current

To understand how your NRG Vault Portable Power Station stores and supplies power it’s important to understand some basic concepts around electricity. Let’s look at the types of current flow in a circuit and how it works with your NRG Vault Power Station.

  1. AC (Alternating Current) – An AC current can change direction (or polarity) periodically within any given frequency. Let’s take 50Hz frequency as an example. This means it will be positive and negative 60 times a second (1 cycle of positive and negative is known as a “full wave”). The main benefits of AC are that it is able to convert its voltage levels with a component known as a transformer. This allows AC currents to be transmitted over long distances which is why we use it to power homes and buildings. AC can come in a number of forms known as “Waves” such as Triangle Waves, Square Waves Pure Sine Waves. Any appliance that plugs into a standard wall socket in a home uses AC current.

  2. DC (Direct Current) – DC only flows in one direction and maintains its polarity, so it is essentially always positive and negative. The main benefits of DC are that it can be stored in batteries while still in its DC form. Any battery powered device will use DC current.

Why can’t we store AC?

Energy is stored in a battery and batteries contains two terminals i.e. positive and negative (+ and -). We can store DC energy because the voltage can complete the circuit properly in a battery due to its positive and negative terminals. But in order to store AC energy in a battery, the battery terminals must change at the frequency of the AC voltage (e.g. 50 times a second). This is not possible as the terminals of a battery are fixed.

This is where inverters come in. An inverter can take a direct current (DC) and convert it to an alternating current (AC). Your NRGVault portable Power station has a built-in inverter that converts DC electricity to AC electricity in Pure Sine Wave form.


Pure Sine Wave is a form of electricity that is stable and is very similar to the electricity that will come out of a standard wall socket.

An inverter works in 3 stages: Oscillator, Booster and Transformer.

During the oscillator stage the direct current is transformed into alternating current. The current can be set to any frequency so an inverter will usually be configured for a specific region. In Australia we use a frequency of around 50Hz so the NRGVault oscillator will operate at 50 full waves per second. During the oscillator stage wave heights are too small to power anything so it will need to be increased.

Electric Flow Illustration

The inverter takes the signal from the oscillator stage to the booster stage to be amplified. After amplification it goes into the transformer stage to regulate the voltage. In Australia the typical voltage range is 220 – 240V. In the NRGVault power station the inverter transformer will step up the voltage to the required value (anything up to 240V) and feed it into the household appliance that is trying to draw power.

When the NRGVault supplies DC power it simply bypasses the built-in inverter because it already stores DC power, and no signal conversion is required.

So now you know how your NRGVault power station handles these.

Amps vs Volts vs Watts – How does it all work?

Electricity is made of 3 basic units: Voltage, Current and Resistance.

Voltage is measured in volts, current is measured in amps, and resistance is measured in ohms.

Volts are the measure of the force at which electricity flows. Think of it as pressure.

Amps or current is the measure of the rate of electricity. Think of it as volume.

Electricity is measured in units of power called Watts.

Circuits are made up of wires of different materials such as copper or aluminium, wires also come in different thickness and length. All of these will affect resistance (Ohms).

The whole system is very similar to how water flows through a pipe.

Current Flow analogy with Water Flow

How much power do I need?

To calculate how much power you need, consider how many watts your appliance uses and how long you use it for.

Watts: 1000W = 1 kilowatt (kW).

Watt hour: A Watt hour (Wh) represents the estimated amount of energy an appliance consumes in an hour.

You can usually find how many watts an appliance uses on its label. If you only know the amps rather than the watts, you can convert to watts by multiplying amps x voltage (A x V = W). For example, if the appliance draws 1.5 amps at 240V then it uses 360 watts.

To calculate in Watt hours (Wh) take the watts of the appliance and multiply this with the average daily hours used. For example, a 20W fan that is used for 4 hours a day will consume 80 Watt hours. The formula is 20W x 4 hours = 80Wh. In another example a 1100W kettle is used only 10 minutes per day, so it consumes 183 Watt hours. We work this out with the formula 1100W x 10 ÷ 60 = 183Wh.

Benefits of Pure Sine Wave

1. Uses the same current as local power grids

A pure sine wave is a type of waveform that is similar to the one from a standard electrical outlet. That means there’s no real difference between plugging your devices into an NRG Vault power station vs plugging them into a wall plug.

2. Minimal risk to devices

The pure sine wave waveform prevents damage to high-end electronics during sudden power losses. This is important when running medical devices or computing equipment that serve important roles and are more susceptible to malfunction when provided dirty power. Alternatively, a modified sine wave inverter when used with devices that have an AC motor such as microwaves and refrigerators, will produce excess waste heat, putting more stress on your devices and decreasing their overall lifespan.

3. Consistent, smooth flow of power

Pure sine wave inverters unlike modified wave inverters, deliver consistent, uninterrupted power to your devices. This is beneficial because modified wave inverters produce power in a step pattern, which abruptly ups and downs the voltage, this leads to inconsistent electricity flow which is damaging to circuitry in the long run.

Pure Sine Wave compared to a Modified Sine Wave

4. Silent performance

When using modified wave inverters, you might hear an irritating humming sound from lights and fans. This will not happen when using the NRG Vault power station as pure sine waves inverters produce very little sound.

5. Wide compatibility

Because NRG Vault power stations produce the type of power we use daily, almost all devices work with them, including:

  • Refrigerators, microwaves, and compressors.

  • Audio and video equipment.

  • Computers and laptops.

  • Medical devices such as CPAP machines for sleep apnea.

Battery chargers, lighting equipment, home appliances, and much more.

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The LiFePO4 Story

LiFePO4 batteries are a type of Lithium battery using Lithium Iron phosphate. The main benefits of LiFePO4 are faster charging, lighter, longer lifetime and most importantly safety. They are much safer when subjected to hazardous events such as collision, short circuiting and won’t explode or catch fire like Li-Ion batteries.

Regular lithium-ion batteries have a high energy density, so they are great for power hungry devices that drain battery at a high rate such as smartphones, laptops, and power tools. Compared to lithium-ion batteries, LiFePO4 batteries have a lower energy density which make them unsuitable for powering small wearable devices and are more effective when used in RVs, boats, solar energy systems, and portable power stations where other components can be combined with the battery tech for more effective use.

Battery Degradation

1 cycle is when there is a complete charge and discharge of a battery. The regular lifecycle of a lithium-ion battery such as the ones used in smartphones is around 500 – 1000 cycles. However in a LiFePO4 battery such as the ones used in the NRG Vault power station the regular lifecycle is up to 5000 cycles. This makes LiFePO4 batteries more resistant to heat and will incur less battery degradation over the same period of time.

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An empty lithium ion battery


Although LiFePO4 batteries are much safer than lithium-ion the same basic safety procedures are recommended to ensure long life for your NRG Vault Power station and any connected devices.

1. Avoid overcharging.

Disconnect adapters and devices after its battery reaches a full charge. Leaving devices on a charging source too long could cause them to overheat and can reduce their battery life.

2. Pick the right charging source.

Only use the adapter and cable that came with your device. If no adapter was supplied or using your own adapter, always follow the manufacturer’s recommend power requirements when selecting a charging source. Take special care to match the correct voltage and amp values your device requires when picking a charger.

3. Charge only on non-flammable surfaces.

Devices and charging sources can get warm or sometimes even hot during charging. Make sure to always place the device and charger on a non-flammable surface when charging. Do not place on beds, pillows, paper, or near any fabric such as curtains or clothing under any circumstances.

4. Avoid extreme environments.

Do not recharge your devices in environments where extreme temperatures can occur. On particularly hot days do not charge in places such as the inside of a car, or an unairconditioned room. If it’s possible, try and wait till the evening when temperatures are a bit cooler.

5. Monitor charging.

Recharge your devices while you are nearby, preferably in the same room or another room close by. This way when there is a defective device or battery you can take it off the power supply immediately.

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