Generators for Hunting 

Disclaimer: Picture of actual produce was chosen because of availability of the picture and the actual produce is not neither evaluated nor endosed by the writter.

The use of generators in the field to supply 120 volt or 12 volt DC power has long been a topic that ultimately ends up in a money vs quality topic. Hopefully this article will help separate some of the facts from some of the fiction.

When it comes to electricity generation, a generator is a device that converts mechanical energy to electrical energy for use in an external circuit. The source of mechanical energy may vary widely from a hand crank to an internal combustion engine which is obviously more convient. [1]

We (myself included) tend to refer to our devices as generators. That terminology is in fact is incorrect. A generator produces DC voltage where as an Alternator produces AC Voltage.

The alternator comprises of three main parts.

The motor

The device that drives (turns) the Alternator - in our case it is almost always a motor that is powered by natural gas, propane, diesel fuel or gasoline (most Commonly Gasoline).

Natural Gas - Not an option for hunting with, as the availability of this fuel is not available in the wilderness.

Propane Power - This is a costlier fuel to use in that it is not as an efficient fuel as gasoline. Thus you will have to bring more fuel by weight. As a fuel it does burn cleaner and does not gum up your Carberator like gasoline does. That saves on costly repairs down the road. Oh, one more point for the negative side, if you are camping in the cold (less than 20 degrees Farenheight). This fuel does not like to power the engine and you will have issues with starting and running the alternator at colder ambient temperatures.

Deisel Fuel - Although deisel fuel is not as readily available as gasoline. It is not entirely out of the question as a fuel source as it is superior in efficiency. The issue with Deisel fueled alternators is in the sizing of the diesel generator to avoid low-load or a shortage of power and is complicated by modern electronics, specifically non-linear loads. In size ranges around 50 MW and above, an open cycle gas turbine is more efficient at full load than an array of diesel engines, and far more compact, with comparable capital costs; but for regular part-loading, even at these power levels, diesel arrays are sometimes preferred to open cycle gas turbines, due to their superior efficiencies. [4] You will generally find that alternators using Deisel fuel are left open to the larger units and are not readily available in smaller units suiteable for hunting requirements.

Gasoline - Most of us don't want a great big alternator to carry into the bush and only want it to charge a few batteries or run a few lights. Deisel power is for large alternators. Cold weather and weight rules out propane, and non availability of Nature Gas brings us back to the dreaded gasoline. I'm sure that everyone knows that ethanol that has be added to today's gas and that the ethanol likes to attack the brass components of the fuel system of your alternator. Gasoline, even with a stabilizer does not have a long shelf life.  So, what can we do. A discussusion with the dealer who recently sold me a new generator advises the following. Run fuel stabilizer in your gas 100% of the time. Also, run your engine out of fuel before storing your alternator. The reason you run stabilizer is because you will not get 100% of the gas out of the carberator.

The Stator

This is the portion of the alternator that is on the outside frame of the alternator. In a brushed alternator it will be either a wound dc stator or a fixed magnetic stator that provides magnetism for the Armature to rotate in and it is the armature that produced the AC voltage. In a brushless alternator, it has wound coils for the alternator and they produce the AC voltage.

The Armature or Rotor

This is the portion of the alternator in the center of the alternator that rotates. In a brushless alternator it may contain a magnetic core where as in a brushed atlernator it will be a wound armature with slip rings. 

The Principle of Operation

A conductor moving relative to a magnetic field develops an electromotive force (EMF) in it (Faraday's Law). This emf reverses its polarity when it moves under magnetic poles of opposite polarity. Typically, a rotating magnet, called the rotor turns within a stationary set of conductors wound in coils on an iron core, called the stator. The field cuts across the conductors, generating an induced EMF (electromotive force), as the mechanical input causes the rotor to turn. [2]

The rotating magnetic field induces an AC voltage in the stator windings. Since the currents in the stator windings vary in step with the position of the rotor, an alternator is a synchronous generator. [2]

The rotor's magnetic field may be produced by permanent magnets, or by a field coil electromagnet. Automotive alternators use a rotor winding which allows control of the alternator's generated voltage by varying the current in the rotor field winding. Permanent magnet machines avoid the loss due to magnetizing current in the rotor, but are restricted in size, due to the cost of the magnet material. Since the permanent magnet field is constant, the terminal voltage varies directly with the speed of the generator. [2]

An automatic voltage control device controls the field current to keep output voltage constant. If the output voltage from the stationary armature coils drops due to an increase in demand, more current is fed into the rotating field coils through the voltage regulator (VR). This increases the magnetic field around the field coils which induces a greater voltage in the armature coils. Thus, the output voltage is brought back up to its original value. [2]

 

PolesRPM for 50 HzRPM for 60 HzRPM for 400 Hz
2 3,000 3,600 24,000
4 1,500 1,800 12,000
6 1,000 1,200 8,000
8 750 900 6,000
10 600 720 4,800
12 500 600 4,000
14 428.6 514.3 3,429
16 375 450 3,000
18 333.3 400 2,667
20 300 360 2,400
40 150 180 1,200

Types of Alternators

Alternators with Brushes

An alternator is an electrical generator that converts mechanical energy to electrical energy in the form of alternating current. For reasons of cost and simplicity, most alternators use a rotating magnetic field with a stationary armature. Occasionally, a linear alternator or a rotating armature with a stationary magnetic field is used. In principle, any AC electrical generator can be called an alternator, but usually the term refers to small rotating machines driven by automotive and other internal combustion engines. An alternator that uses a permanent magnet for its magnetic field is called a magneto. [2]

Alternator with Brushes

Principle of Operation of Brush type alternator

Brushless Alternators

 

Brushless alternator

Brushless Alternator Illustration

 

Principle of brushless Alternator [1]

A brushless alternator is composed of two alternators built end-to-end on one shaft. Smaller brushless alternators may look like one unit but the two parts are readily identifiable on the large versions. The larger of the two sections is the main alternator and the smaller one is the exciter. The exciter has stationary field coils and a rotating armature (power coils). The main alternator uses the opposite configuration with a rotating field and stationary armature. A bridge rectifier, called the rotating rectifier assembly, is mounted on the rotor. Neither brushes nor slip rings are used, which reduces the number of wearing parts. The main alternator has a rotating field as described above and a stationary armature (power generation windings). [2]

Varying the amount of current through the stationary exciter field coils varies the output from the exciter. This output is rectified by a rotating rectifier assembly, mounted on the rotor, and the resultant DC supplies the rotating field of the main alternator and hence alternator output. The result of all this is that a small DC exciter current indirectly controls the output of the main alternator. [2]

Inverters

Now this is a generator, in that it produces DC power. Read on, I said it right. It produces DC Power. It also, has additional circuitry that converts that DC into AC (thus the name inverter). That is why these units cost so much more. This type is generally the quietest of all the generators/alternators, most fuel efficient of the bunch, produce the cleanest power and are now readily available from most manufacturers.

Inverter generator

 

So What do you buy?

Both the brushless and brush type alternator are often refered to as a contractor's generator, because contractor use them for running power saws, table saws, air compressors, etc.

Alternator Contractor Unit

Contractors Alternator

Couple of things to mention though. These alternators are generally available at a cheap price in larger power ranges. In terms of clean power these two type produce dirty power with many voltage fluctuations that can destroy a sensitive electronic device. With the brushless generally being the dirtier power producer of the two. 

In a nutshell, if you are running larger loads and NO ELECTRONIC DEVICES these units can be the way to go, especially if money is a key factor. Example: you can purchase a 2300 watt top name brand alternator (generator) for $1000.00 (CAD) and chineese knock offs go for much less. (ball park $600.00). You can reduce the risk of electronic damage on the contractor units by installing a good surge suppressor that will provide CLEAN power (make sure that the units states it provides clean power) , or a Uninteruptable Power Supply (the later being the better, costlier, and heavier of the two units.)

The inverter generator on the other hand has a much higher price tag in that the same company retails its 900 watt inverter for $1,100 CAD and an 1,600 watt inverter for $1,300 CAD with knock offs going for $800.00 or less. But, I don't have to worry about running a TV or DVD in my RV with this device. No need for a surge suppressor, I also believe that over the years I have lost a bread maker and a DVD player from a contractor unit.

My initial response was to run out and purchase a knock off inverter. But what one? This is when I started to have a problem. Sparked by my own personal motive to purchase a new Generator for my RV, I wanted something reliable and did not want to pay too much.

I personally owned a name brand unit and retired it not too long ago after 32 years of hard commercial use.

In the mean time over a short period and a couple of knock offs that have already fallen by the wayside with light hunting use, they have seen their day.

How Big A Unit Do You Need?

This is always a good question, and the answer always starts with you. What are you going to power or what do you thnk you are going to power down the road. In my case, I see that for 90% of the time I will recharge my RV batteries (!2.5 volts @ 6.5 amps = 81.25 watts), for the other 10% of the time I may run the microwave (1000 watts), or the TV and DVD. The odd time may be a power saw or drill. Look at the devices that you may want to power and they should have a lable that tells you how much wattage they will take to run. Add up the total and that is your requirements.

And don't kid yourself, I will NOT be able to run my air conditioning unit.

Alternator Sizing

Ok, I've determined that a 1000 watts is all that I need and one of the manufacturers makes a 1000 watt unit. Maybe this is a good pick.

WRONG - if you look carefully you will see that manufacturers have TWO numbers for wattage.

Maximum AC Output (watts / amperes) - This is the maximum that the unit could deliver for a very short period (measured in seconds, not minutes).

Rated AC Output (watts / amperes) - Continuous Use - This is the maximum wattage that the alternator/generator can deliver all the time.

So, the next size up for two hundred dollars more is a 2000 watt alternator/genertor. But that unit is only good for 1600 watts continuous.

But that is more than enough for my needs.

If my wife insists on running the air conditioner, I will need a bigger unit.

And constraint. I should know better than to try and run the microwave and a power saw at the same time. 

Generator/Alternator Noise

Another number that should be important to you is the Noise Level (@ 7 metres).  48.5 - 60.5 Db

This means that the unit will produce 48.5 db at 1/4 load and 60.5 db at full load. (some say that this is equivalent to a person talking)

Most people will look at these numbers and say that 60.5 DB at full load is only is only 1.25 times louder than the 48.5 DB at 1/4 load.

WRONG - The decibel (dB) is a logarithmic unit used to express the ratio of two values of a physical quantity. One of these values is often a standard reference value, in which case the decibel is used to express the level of the other value relative to this reference.

The number of decibels is ten times the logarithm to base 10 of the ratio of two power quantities. A change in power by a factor of 10 corresponds to a 10 dB change in level. At the half power point an audio circuit or an antenna exhibits an attenuation of approximately 3 dB. A change in amplitude by a factor of 10 results in a change in power by a factor of 100, which corresponds to a 20 dB change in level. A change in amplitude ratio by a factor of 2 (equivalently factor of 4 in power change) approximately corresponds to a 6 dB change in level. [5]

To cut it short every rise in 3 db is twice (2x) as loud as the number before it.

48.5 Db is the quietest it can be

51.5 Db is twice as loud.

54.5 DB is twice as loud as 51.5 but 4x as loud as 48.5

57.5 DB is now 8 times as loud as the original 48.5

and finally.

60.5 DB is 16 times as louder than 48.5 DB.

My choices are simple, try to run at reduced load or place the unit farther away from the RV so I don't hear it. I know I'll put it beside Mike's trailer and keep him awake at night.

All kiding aside. If you are going to use this in a campground you will not be a appreaciated.

Research

Okay, I know what kind of alternator/generator I want,  I have my sizing picked out, and I want a quite unit. Time to choose a brand.

You will note that I don't come out and name brands of alternators or generators. Do your own research, search for a Name Brand Generator Problems, Name Brand Generator Issues, Name Brand Generator Warranty Repairs, and Name Brand Generator Better Businness Bureau complaints. If your really good you can also search for law suits. Search the units that peak your interest. You will be surprised at the name brand units that have many problems reportly not supported by their so called warranty.

It will not be long and you will have ruled out a bunch of alternators that you would not want to risk a purchase with, the ones with no issues and no complaints, lots of service centers (make sure that there is one near you.) are probably not a bad choice in that they should be reliable.

Try to find out if the unit has copper or aluminum windings. In the long run, you want copper. For that same reason that they don't wire houses with aluminum anymore. Long term corrosion and in the case of an alternator heating issues aluminum coils have much more heating issues that copper due to the expansion properties of the aluminum vs copper.

Now you have a short list. Try searching for parts. Most of the ones left will let you buy a Carberator, but can you buy rings for the engine.

Search out some videos, I was shocked to see generators with stators held on by ty raps. Yes, Ty-raps, when the stator heats up (and aluminum stators are more prone to heat issues) the ty rap melts and the stator falls off. Can you buy a new stator?

It is my personal opinion that most of these knock offs are throw away units when things go bad as most parts are not available to the public.

It was also my personal opinion that the purchase of a name brand unit that the others are trying to copy was the way to go. There is a good reason why they are being copied or making their unit LOOK LIKE IT.

It is my personal opinion that you get what you pay for.

Alternator Features and Choices.

Sizing - I think we have covered that.

Generator / Alternator type - Brushless, VS Brush Type VS Inverter.

One of the features that I looked for and insisted on was a 12 volt outlet. Make sure that it has a voltage regulator (if it does not come with one you can purchase an 8 amp solar charger and use that.) Make sure it also comes with a cord. That way you don't have to worry about over charging your battery. {The other option of course is to use a 120 Volt AC to 12 Volt DC charger, as most of you probably already own one.)

Get a cover for your new purchase. It saves a lot of wear and tear on the unit.

Purchase a spare spark plug. Vacuum seal it in a bag and keep with the alternator for use down the road. (hopefully never).

Issues with Alternators

You have done your research and you have purchased what you believe to be a good choice.

I will point out to you a few things.

On a gasoline powered unit, like I stated earlier run stabilizer in your gas and don't leave fuel in the alternator.

Another misconception is the statement, "I purchased the generator new three years ago and I have been storing it ever since. Now when I need it. It does not work." Willing to bet the alternator starts and runs but it does not produce electricity.

Alternators have residual magnetism in them and if you let it sit. It will loose that magnetism. It is the manufacturers recommendation on any alternator/generator to run it a minimun of 15 mins per month at near load (some manufactures suggest longer run times). This is not for the engine, lubrication, nor bearing run in. But rather to keep the magnetism in your generator/alternator built up for when you do need it. If the alternator / generator looses its magnetism. It will not produce power.

Finally, never start your alternator/generator with devices plugged into it. The alternator on start up will typically surge on and off and can damage items that you have plugged into it via either overvoltage or undervoltage. The generator with a load on it will also have a hard time stabilizing its running speed. That load is hard on the alternator's exciter circuit and especially on brushless alternator's. Typically it is the capacitor on the brushless alternator that blows and leaves you powerless.

References

[1] https://en.wikipedia.org/wiki/Electric_generator

[2] https://en.wikipedia.org/wiki/Alternator

[3] https://en.wikipedia.org/wiki/Single-phase_generator

[4] https://en.wikipedia.org/wiki/Diesel_generator

[5] https://en.wikipedia.org/wiki/Decibel

Article Images

Principle of Operation of Brush type alternator - By Federal Aviation Administration - http://www.faa.gov/regulations_policies/handbooks_manuals/aircraft/amt_handbook/media/FAA-8083-30_Ch10.pdf,

Public Domain, https://commons.wikimedia.org/w/index.php?curid=28091272

Brushless Alternator Illustration - By Egmason - Own work, CC BY 3.0, https://commons.wikimedia.org/w/index.php?curid=10250453

Kipor Inverter - By OMittmann (Own work) [CC BY-SA 4.0 (http://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons

Contractors Alternator - By Powernowllc [CC0], via Wikimedia Commons

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