Articles Home > All Articles > Power & Electrics > Generators

Generator Power

The generator, which was discovered by Michael Faraday, is an ingenious device that converts mechanical energy into electrical energy. Today’s popular camping generators use fuel powered engines to create this energy. They are a great companion to have when travelling in the outback because as long as you have the right fuel, you will have electricity. In this article, we look at the case for using a generator as your main power source when you're at camp and your vehicle is stationary.

Why Take a Generator?

Obviously, the starting battery in any car or motor vehicle is a good electrical power source, with its main role to deliver a short burst of high power to start the engine. As we’ve already covered in our Battery Power article however, travellers/campers who rely on their vehicle’s power are recommended to set up a dual battery system . Any power usage when the vehicle is not running draws off the auxiliary battery, which is then recharged when driving commences. This works well for a couple of days depending on usage. However, in all likelihood, travellers will find themselves in situations where their battery usage is depleted well before they plan to drive the vehicle again. In this article, we’ll look at the case for using a generator as the power source.

Benefits of a Generator

Power at any time - and lots of it! - you know in advance how much power you will have available, even if you don’t see the sun for a week. You can recharge your batteries in a few hours while you are at camp - rather than wonder if your solar panels will still be there when you get back to camp that night.

You can take along the luxuries you are used to at home - air-conditioning, electric-blankets, big fridges, microwaves etc.

When you’re not travelling, you can use the generator during blackouts, or to power appliances away from home.

Low cost and weight - currently a petrol generator will need less upfront expenditure and weigh less than any other method of generating several kVA of power.

Electrical Terminology

Electrical power is measured in Watts - a bright light bulb uses 100 watts and the maximum that can be drawn from a home power point is 2400 watts - also known as 2.4 kilowatts or kW.
You may see output as kVA, and for many appliances this is the same kW, but for those appliances with motors in them, the kVA needed can be up to 50% more than the kW needed.

If the generator has a rating like 2400 watts and 1800 watts at 0.8 PF (Power Factor), this is just another way of showing the kW and kVA rating. When the PF is 1.0 then kVA equals the KW rating.

Two numbers are used to describe the output of a Generator - Peak and Continuous.

Peak describes the output deliverable for several minutes - the generator’s components won’t blow up at that amount of load, but they will heat up quickly.

Continuous ratings are usually limited by the heat that needs to be removed when running continuously.

Since the Peak is always more than Continuous, not surprisingly most Generators are described by their Peak output (Inverters are the opposite !).

So you may find that an 850 Watt generator can really only run a 600 watt load continuously. Ideally you would find out the Peak and the Instantaneous ratings of your appliances and check that they were less than the Generator output. But you can’t rely on this because most appliances don’t state the start-up or peak power needed and the length of the peak really needs to be known too.

Unfortunately the only way to be sure, is to test the appliance with the generator. Tables of power needs for appliances and compatibility with Generators (and Inverters) are available, but again, they’re only a guide.

Battery Charging & Generators

Even the under-$100 generators have so-called “12 volt DC” outputs on them - but never connect any 12 volt appliances to them - the output is only suitable for battery charging. The output can be over 20 volts under light load and the output is very rough DC that could damage many appliances.

These charging outputs only give slow charging for car-size batteries - a 1kVA Generator can only provide one tenth of that power from the Charging output. But the biggest concern is that there is NO charge regulation at all, so if you don’t disconnect the charger when your battery approaches full charge, you could destroy an expensive battery!

TIP	For any serious charging you are better off buying an automatic 240 volt charger - you can now get 15 amp Three Stage Chargers for around $100.

Choosing a Generator?

Fuel Type

2 stroke - the lowest cost, but you have to put up with the disadvantages of 2 strokes - more noise, more fuel consumption, smelly exhaust fumes, plugs fouling etc.

4 stroke - most smaller generators are 4 stroke and all of the mid-priced generators are 4 stroke.

Diesel - these are only available from 2kVA and up, and have the advantage of less fuel usage than petrol and usually means you can have the same fuel for vehicle and for the generator. It also eliminates the explosion hazard of petrol.

LPG - only available for a few models of generator.

Electrical Output

Non-Inverter

A few years ago, all generators had the output connected directly to coils being rotated in a magnetic field and thereby generating a reasonable sinewave-shaped voltage output.
But to ensure the output had a frequency of 50 Hz (Hertz or cycles per second), just like the mains AC (Alternating Current), the engine had to be governed to run at 3000rpm, even when putting out very little current. If the generator is being used for low loads (a few lights, charging small appliance batteries) this meant a lot of un-necessary noise, engine-wear and fuel consumption. Whenever a bigger load was connected to the generator (or removed) the electrical regulator would have to change the magnetic field instantly - and this leads to surges on the output that can damage appliances or blow fuses.

Sine Wave Inverter

Most small Inverter Generators go to the additional cost of using a Sinewave Inverter. This means that appliances that have timers in them or that are confused by non-sinewave outputs will work correctly.

It’s hard to predict whether a particular appliance will need sinewave output e.g some Notebook computer power supplies will work perfectly on modified squarewave, whereas another may overheat and damage the Notebook battery.

Modified Square Wave Inverter

If you convert the generator output to DC, then you can run the engine at any speed that provides enough power. The internal DC is converted to AC at 240 volts and 50Hz using a totally electronic Inverter. If you have no load on the Generator it will run at idle, so if you now connect a heavy load, the engine needs to go to full rpm to provide enough power, but that can’t happen instantly. That’s why Inverter Generators have the option to switch off Eco or Smart Throttle, to run the generator at high revs, even with no load. Simple low-cost Inverters don’t give a pure sinewave output like mains 240 volt, but their modified square-wave output is good enough for most appliances.

12 Volt Only

If you don’t have any 240 volt appliances and just need a source of more 12 volt power to keep your batteries fully charged, then there is an Australian -made petrol-driven generator which only provides a regulated 12 volt output.

TIP	If you are having problem with load surges (e.g.air-conditioners, big fridges), leave a 50 watt lamp always connected to the output.

Construction

The traditional design meant mounting the engine and the alternator on an open frame that made cooling and maintenance access easy.

However to reduce noise, the quieter generators are enclosed in a metal or plastic housing.

Optional Features

Shown below is a list of optional features that you may encounter in regards to generators.

Low Oil cutout

A low oil warning is important, but only if there is someone nearby to hear it - it is far safer to have a cutout which stops the generator in case of low oil.

Overload Cutout

Not really optional, but the more sophisticated ones will protect against over-temperature as well as over-current, over-voltage or under-voltage (that can damage some appliances)

Fuel Gauge

It’s easier and safer than having to open the fuel cap!

Earth leakage protection

Bigger generators may have these built-in, but they can be easily added.

Meters

You can get by without voltage, current or frequency meters, but with them it’s easier to check if your system and appliances are healthy or if you are close to overloading your generator.

Battery Charging output

Whether you buy the cheapest two-stroke or the most expensive Japanese Inverter generator, the built-in charger is still totally unregulated and you could cook your batteries in a few hours. Consider this an emergency option only, unless you like living dangerously.

Eco/Smart throttle

Nearly all Inverter Generators have this built-in to reduce fuel use, noise and wear.

Paralleling two Inverter Generators

You can directly wire the DC from two batteries together, but you can’t do this with AC because the voltage changes from plus 335 volts to minus 335 fifty times a second. If you connect them at the wrong time there’ll be a big bang ! The outputs from two AC generators can only be connected together to power bigger appliances if the generators are synchronized so that positive peaks occur at the same time. This requires a special cable and connections, so if you need this capability, check before buying your Generators.

Safety with Generators

Ventilation

When running, the Generator will put out dangerous gases, so check where the exhaust fumes will drift. It will also put out heat from the exhaust and vents that can lead to a fire if something flammable falls on the Generator. When the Generator is stored it will give off Petrol fumes that are an explosion hazard in a non-ventilated space. When refueling the Generator, all nearby flames must be off (e.g Three-Way fridges, campfires, Gas Lamps).

Generator Disadvantages & Limitations

Noise

One of the benefits of going bush is the beautiful peace and quiet and the wonderful nature sounds, but even the quietest generator still produces some noise. You can minimise the impact of the noise on people by selecting the time of day you use it, where you put it etc, but in some National Parks they are banned and in other locations (i.e. near anyone with solar power) it’s just anti-social to spoil the bush silence.

TIP	The noise at the campsite from the generator will be lessened if you place it in a dip or hollow and if you can put it behind a solid object - a rock, sand-dune, big tree etc.

Fuel

You have to work out how much fuel you will need for the trip and then find the space for it and store it safely - having the same fuel as your vehicle engine helps here.

Reliability

Any machinery will be less reliable than the zero moving parts in a solar system! When in a remote area, having your generator break down is more than a nuisance - your food supply for the trip may perish.

Maintenance

If you aren’t mechanically inclined, then you need to consider where you can get servicing done around Australia, in case of problems on the road. The average mechanic will have problems with the electronic controls of an Inverter generator. The warranty service for the same brand of generator varies depending on who you buy from - some have a nationwide network, others require the generator to go back to the supplier. Consider this when looking for the cheapest supplier for the same brand.

Alternatives to a Generator

You could use an Inverter to supply 240 volt from your battery, but you would need really big batteries to provide the power that a 2kVA generator with 5 litres of fuel can supply. To run a 2kVA Inverter you would be drawing 200 amps from your battery.

Solar

The silence and zero running costs of solar are great, but you only have power for limited hours of the day and only on sunny days. But 1kVA of solar panels will cost around ten times as much as a 1kVA generator. You will also need bigger batteries than with a generator, to provide power when solar power isn’t available - and batteries are heavy and need to be replaced

Using 12 volt appliances

Many appliances are available as 12 or 240 volt versions (fridges, microwaves etc), but the 12 volt version always uses less power and is always more expensive! A 12 volt fridge will have thicker insulation and use a more efficient motor because mains power is cheap ! A 12 volt microwave will use less power because there are no losses in converting the 12 volts to 240 volts first. Using only 12 volt appliances may reduce your power needs so you won’t need a generator to provide more power.

Car Alternator

Modern vehicle Alternators can deliver up to 1.5kVA for a limited time, but it just isn’t practical to use your car engine for long periods of battery charging when stationary. You will use much more fuel and you will have problems with the engine bore glazing.

Bigger Batteries

If you only go away for a few days at a time, you can take more power with you rather than generating it while away - but batteries are heavy and need to be replaced.

Wind Generators

These are very practical on yachts and they keep getting cheaper, but are only useful for land travelers where there is regular wind and few trees.

Fuel Cells

In the next year we will see Fuel Cells powered by Methylated Spirit that will silently power a Notebook Computer for 8 hours at 50 watts - but don’t put off your travel plans waiting for a 500 watt Fuel Cell to cost anywhere near Generator prices!

Comments & Reviews(167)

Page Stats

Article By: ExplorOz Team

Created: June 2008
Revised: June 2007
Latest Feedback: December 2019