Choose the right machine

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Where to start?

If you are trying to decide which Honda generator to buy, it helps if you can prepare a list of equipment that you will be running and the power consumption specified on the rating plate. Power consumption is usually specified in Watts or Amps.

Power (Watts)= Volts x Current(Amps)

From this you will see that 1kw is roughly 4 amps at 240v

Knowing the power consumption on the rating plate of your equipment is a good start but it’s not the whole story. Some loads are resistive and will only use the power specified on the rating plate. Other loads like fridges, motors, freezers, compressors and ballasted lights are inductive. Inductive loads will require consideration to made of the starting currents, which can be a multiple of the power specified on the rating plate. In some cases, cunning modification of the equipment can reduce starting currents dramatically. These modifications are not always incorporated by the original equipment manufacturer as they have not envisaged the equipment being supplied by a portable generator. For those thinking of running a compressor then you might benefit from the article on my blog Overcoming high starting currents in air compressors.

A word about electric motors in general.

Electric motors are designed to attain full speed in a given time, typically one or two seconds. Before that, the electrical power fed to the windings is heating them rapidly. So you don’t want a generator that fails to get the motor started promptly. If the motor is designed to get up to speed in two seconds and the generator takes ten seconds to get it there then expect the life of the motor to be very much curtailed.

Here’s a table showing some typical loads.

equipment Watts Starting Watts
fridge freezer 500 1500
portable refrigerator 100 300
small microwave oven 650 1600
portable fan 40 100
hedge-trimmer 500 1500
portable air conditioner 3000 5000
unmodified compressor 1500 6000
typical hand power tools 500 1000
Kettle 3000 3000
travel kettle 650 650
PC 320 700
laptop 40 100
fluorescent lights 58 120
central heating pump 250 500

It’s tempting to choose a generator with a considerably larger capacity than will ever be used. This can be a mistake. Generators that are consistently loaded far below their rated capacity will become clogged with carbon and experience problems sooner than a wisely chosen Honda generator that matches the load requirement.

Consideration must be given to the quality of the electricity supplied and how closely its voltage is controlled. Some equipment like electric drills and power tools will happily run from a simple frame generator without sophisticated voltage regulation. Sensitive equipment like televisions, battery chargers and inverters will require a more closely regulated supply.

What about kVA

Also known as apparent power.  kVA x power factor = kW.  Power factor is a measure of a machines efficiency and most Honda generators claim a power factor of about 1. So in a perfect world kVA and kW are the same thing.

In practice the term is so misused and misunderstood as to be worthless. Often manufacturers quote kVA based on the maximum power output of the engine rather than the actual output available from the alternator.  Sometimes they put a large capacity alternator on a smaller capacity engine. When you put a big alternator on a small engine what you end up with is less power. Maximum power and efficiency is achieved by matching the capacity of the alternator to that of the engine so that power is not wasted spinning an alternator heavier than necessary.

The bottom line is this:

a GX160, 160cc, 5.5hp generator will give about 2.2kW continuous

a GX200, 200cc, 6.5hp generator will give about 2.8kW continuous

a GX240, 240cc,  8hp generator will give about 3.2kW continuous

a GX270, 270cc,  9hp generator will give about 3.6kW continuous

a GX340, 340cc,  11hp generator will give about 4.3kW continuous

a GX390, 390cc,  13hp generator will give about 5kW continuous

The figures given above are for open frame generators and are based on experience. Maximum power output is usually about ten percent higher than the continuous rated output and is advisable for no more than a few minutes at a time.

Before people with a physics CSE start getting out their calculators, bear in mind that the horsepower quoted for the various engines is available at 4000 rpm. 50hz portable generators run at 3000 rpm. 60hz portable generators run at 3600 rpm.

Inverter generators can squeeze out a tiny bit more power because the generating apparatus is lighter, so the engine has less weight to spin. Also the output frequency is not dictated by  engine speed so they can run a little faster.  Often the extra potential of inverter generators is offset by them being silent runners with larger exhausts and air filters that limit power..

Genuine Hondas or Chinese knock offs, the same rules apply. There is no magic spell that makes a GX270 give 5kW.

The catering wagon conundrum.

Catering wagons usually run fridges and freezers as well as tea urns or kettles. The largest load is likely to be the tea urn or the kettle. With a 2.5kw kettle, 1kw of fridges and 100w of lighting, you need 3.6kw of capacity. However, most of the time the generator will just be running 100w of lighting.  Only occasionally will it have to power the kettle. The fridges are turned on and off by a thermostat so they are idle much of the time.

This creates two problems

1) Generators don’t like to run way below capacity.

2) The Honda range of inverter generators are available as 1kw, 2kw, 3kw and then a massive jump to 5.5kw machines. You could be buying a 5.5kw generator that spends most of its time running 100w of lighting.

I have a solution. The ” Rice Powered Knitting Machine” is a box with two ordinary 13A wall sockets on it.  A lead with a 3 pin 13A plug goes into any 13A outlet being supplied by your generator. Into one socket you plug your fridges, into the other your kettle or tea urn. When the kettle or tea urn starts drawing power, the socket powering the fridges is disabled. In this way the load gets distributed over time and the generator spends less time idling. Also you don’t need to lug around such a big generator.

In the example given above the maximum load is reduced from 3.6kw to 2.6kw. This reduces the generator requirement from a Honda EU65is weighing 100kg  to a Honda EU26i or EU30is weighing 50kg. 

I make them to order for £90.

rice powered knitting machine

And, just in  case Victor Kyam is watching and in the mood for a spot of rash investment, here is another idea for those with catering wagons.

What about Battery chargers?

Now there’s a subject that techies can really get their teeth into. I’ll stick with the condensed version. Power factor is the key. You can figure out the basics from good old P = V x I. If you have a 14v charger putting out 10 amps the power is 140watts. However that does not mean you need a 140w generator to run it. That’s where power factor comes in. Cheap chargers have a power factor of 0.5 or thereabouts, meaning they are roughly 50% efficient. More sophisticated battery chargers have power factors approaching 1 (or unity as we say in Star Trek club). So if you have a cheap 10A charger, you need 14v x 10amps = 140w, divided by the power factor 0.5 =280w, plus another 150w to give a bit for the wind (as they say at Boeing). Look for the power factor in the spec. That’s it. I’m done on battery chargers.

So that’s my rougher than rough guide but here’s a link to a guy that knows everything about batteries and battery chargers. Sterling Power

Oh yeah, one more thing. Don’t go blaming all your battery charger problems on your generator. For modern computerised chargers like the Victron Mutiplus there are parameters within the software that you will need to adjust to match the generator to the charger. You need to download the software and play around. I hear plenty of tales of Victrons constantly clicking in and out when running from a generator. Read the manual and set the parameters properly. Victrons are all based on the HAL 9000. If you are having trouble with the Victron then you will probably be glad you read this article on my Blog.

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Which fuel is best? diesel, petrol or LPG

There is a perception that diesel generators are superior in terms of fuel economy and durability. This is true for large capacity, heavy, four pole 1500rpm generators. However the situation is quite different for two pole 3000rpm machines (a description that encompasses almost all portable Honda generators).

A petrol engine has a compression ration of about 9 to 1.  A diesel has a compression ration of 20 to 1. Diesel engines are much heavier than an equivalent petrol engine because they have to withstand the higher mechanical stresses resulting from a 20:1 compression ration. Almost all portable generators are “direct drive” (the alternator is bolted directly to the engine). It is difficult to isolate the alternator and electronics of a direct drive diesel generator from the vibration produced by the engine. They can simply rattle to pieces.

Two pole, 3000rpm diesel generators are noisier, heavier, smellier and hugely more expensive to service and repair than the equivalent petrol generator or LPG generator.

Escher  A curse
by W.H. Auden

Dark was that day when Diesel
conceived his grim engine that
begot you, vile invention,
more vicious, more criminal
than the camera even,
metallic monstrosity,
bale and bane of our Culture,
chief woe of our Commonweal.

How dare the Law prohibit
hashish and heroin yet
licence your use, who inflate
all weak inferior egos?
Their addicts only do harm
to their own lives: you poison
the lungs of the innocent,
your din dithers the peaceful,
and on choked roads hundreds must
daily die by chance-medley.

Nimble technicians, surely
you should hang your heads in shame.
Your wit works mighty wonders,
has landed men on the Moon,
replaced brains by computers,
and can smithy a ‘smart’ bomb.
It is crying scandal
that you cannot take the time
or be bothered to build us,
what sanity knows we need,
an odorless and noiseless
staid little electric brougham.

Which type of generator? Capacitor compensated, AVR controlled or Inverter

There are three broad classes of generator produced by Honda

Capacitor compensated (Honda EC & ECM ranges)

AVR controlled (Honda EB, EG and EM ranges and also the EX4000s, EX5500 and EX10D)

Inverter (Honda EU range and the EX350, EX500)

Capacitor compensated generators

This is the most basic type of generator and for many applications it will be the best choice. It is a very simple design with a minimum of bits to go wrong. It is the cheapest type of generator for the same reason. Drills, saws, power tools, heaters, kettles, halogen lamps, pumps, blowers will all run quite happily from a capacitor compensated generator. Capacitor compensated generators are not all suitable for sensitive equipment like TVs, computers, battery chargers and so on. This is why:

A typical capacitor compensated generator will produce its rated voltage at 3000rpm. The voltage is directly related to engine speed. The engine speed is controlled by a mechanical governor which adjusts the throttle as engine speed varies. When a load is applied the engine will slow down. The governor will respond, opening the throttle to compensate. In the time between the load being applied and the engine getting back to the right speed there will be a dip in the voltage corresponding to the dip in the speed of the engine.

The reverse situation also applies. A generator running under load will speed up when a load is removed until the governor mechanism brings the engine back to its proper speed. In the time between the load being removed and the engine speed being corrected there will be a peak in the voltage corresponding to the peak in engine speed.

A risky scenario would be a 50w TV and a 3kw kettle both run from the same 3.5kw generator. The kettle boils and switches off causing the generator to speed up momentarily, presenting a voltage spike to the TV.

As the generator gets bigger, the momentum within the engine increases and the governor will take longer to reign in the engine speed. Small suitcase generators that are capacitor compensated present negligible voltage fluctuations. There is so little momentum within the engine that the governor is able to operate almost instantaneously. Most conventional generators over 2kw have a near perfect sine wave. Smaller conventional generators have what is known as a zero point crossing spike caused by interference between the poles in a very small rotor. This produces a small glitch that can confuse some battery chargers.

The natural fluctuations in voltage produced by a capacitor compensated generator are perhaps less significant than the voltages which can result from a fault situation. If the governor’s control of engine speed is lost through wear, damage or interference, voltages can exceed 450 volts.

Some capacitor compensated machines have better voltage stability than others but if your equipment is sensitive, caution and further research is advisable.

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AVR or Automatic Voltage Regulator controlled generators

Automatic Voltage Regulators overcome the voltage fluctuations of capacitor compensated generators by varying the strength of the rotor field. When the engine speeds increases, the AVR reduces the current to the rotor, reducing its magnetic field thus reigning in the voltage. When the engine slows, the AVR turns up the current to the rotor to increase its field, stopping the output voltage from dipping. In most cases the stationary AVR feeds the spinning rotor via carbon brushes and slip rings.

An AVR controlled generator has a more closely controlled voltage than a capacitor compensated generator but the frequency will still vary in the same way. When used to run an old-fashioned record player one would hear the speed wobble as loads were applied and removed but with the AVR machine there would be no accompanying smoke effects as the record player fries.

AVR controlled generators are suitable for sensitive equipment. They are also better at starting heavy inductive loads like motors, compressors etc. than a similar capacitor compensated machine They are more complex than a capacitor compensated machine so they are more expensive.

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Inverter generators

Inverter technology allows close control of both voltage and frequency. Inverters are not slaved to the 3000rpm engine speed requirement of other generator types. They can produce the correct voltage and frequency whether they are running at 500rpm or 4000 rpm. They just cannot produce as much current at the slower speeds. This opened the way for Honda to introduce ECO throttle. ECO throttle allows the generator to respond to the load and adjust engine speed accordingly. If the load is small the generator will just tick over quietly and economically. If the load is increased the generator will speed up just enough to meet the demand. It’s all very ingenious. See my blog for more details on the use of ECO throttle with heavily inductive loads.

Inverter generators initially produce three-phase electricity which is fed to the inverter pack. The inverter pack processes this and outputs single phase electricity at precisely 230V 50hz. The sine wave of modern Honda inverters is mathematically pure, making them perfect for running even the most sensitive equipment. The advent of pure sine wave generators enabled equipment manufacturers to improve the efficiency of camping and caravanning equipment like battery chargers and the famed Victron inverters. As a consequence some modern chargers and caravan inverters can only be run effectively from pure sine wave inverter generators. Beware! Not all inverters are pure sine wave inverters. There is another type called a modified square wave inverter. Honda only manufactured one modified square wave inverter and that was the EX350. However it is a common type among competitor machines. Square wave inverters have a wave form that looks like the Manhattan skyline. It is not what you want for your Victron.

These inverters are pretty great and we are not done yet. The nature of inverter technology is such that the size and weight of the generating apparatus is radically reduced, making inverter machines significantly lighter and more compact than conventional generators. The downside is that inverters are the most expensive machines of all. There are some roles that they will not execute as well as an AVR machine. They are not ideal for protracted inductive loads like large ballasted Sodium and Mercury lamps. When running this type of lamp an inverter generator needs to be of considerably larger capacity than the light in order to avoid problems of overheating in the inverter pack. Often it’s more practical to use an AVR controlled machine for these particularly difficult loads.

Recreational vehicle generators.

These are machines designed to be permanently mounted in a camper van  or similar. They are generally very expensive. The make to go for is Dometic (which use Honda engines). I prefer the older simple “h” series machines over the newer “tec” series inverter ones.

Telair also make very good machines. They are remarkably similar to the Dometics but using Yamaha engines.

Honda make an RV generator called the EV3610. My advice is don’t buy a Honda EV3610.

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Welding generators

I’m a DIY kind of welder myself and I approach the subject of powering welders with some trepidation and no pretense of any great expertise. I do however know enough to say that generators and welders will destroy one another if not properly matched. The best option is to buy a dedicated welder generator. Failing that, use the simplest possible type of generator avoiding such sophistication as AVR control or inverters.

This seems like a good juncture at which to note that there are inverter generators and inverter welders and that the two are unrelated. Inverter welders are a very tricky thing to run from a portable generator. Some claim to be OK for use with generators. Personally they all make me nervous. Basic inverter welders are designed to run from the mains and are definitely unsuitable for portable generating equipment. When I say unsuitable I mean it will fry the bejesus out of your generator. Generator Friendly and Generator compliant inverter welders will not get blown up by the voltage fluctuations of simple generators and will hopefully avoid destroying the electronic circuitry in more complex generators.

Well that exhausts and probably over-reaches my understanding of the subject of using welders from portable generators. You may want to do some study before diving into a purchase for the purpose of welding.

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A few thoughts about Honda silent generators past and present

Below is a quick summation of my impressions of the various Honda silent generators. More detailed specifications can be found on the new and used generator pages.

Honda EX350 inverter

For light weight it can’t be beaten at 8.5kg. Has two modes, slow 150w and fast 300w. In the slow mode the Honda EX350 is one of the quietest generators too. But beware the Honda EX350 is not a pure sine wave inverter. This means it probably won’t run your mercury lamp (nods to moth men out there) or your battery charger, but it will safely run TVs lights etc. Edit for the Moth men (entomologists) out there: I have recently found that the EX350 can run the 125w mercury vapour lamp but it is necessary to change the power correction capacitor in the lamp to a higher quality one. Full details can be garnered from:

Paul Butty

or telephone 01909565564

Honda EX500 inverter

A two-stroke inverter identical to the Honda EX350 but…. The Honda EX500 has more power and it is a pure sine wave inverter so you can run anything under 450w. The Honda EX500 was never produced in the same numbers as the Honda EX350 and so is frustratingly rare. It was soon replaced by the disappointing Honda EX7.

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Honda EX650

If quiet running is what you need then the Honda EX650 trumps all comers but quiet running is not the only thing that made the Honda EX650 a true design triumph. The Honda EX650 is the most durable and repairable machine I have come across. The engines are bullet proof and even after many thousands of hours service the most that is usually required to bring them back to as new condition is new piston rings. The controls are fantastic with everything done by one simple knob. It’s a doddle in the dark.

Honda EM650

is just an EX650- with a long run tank. The Honda EM650 is a smidgen louder than the Honda EX650 but if you need to run all night without a top up then the 7.5 hour tank is just the ticket, making the Honda EM650 a winner for campers.

Honda EX7

It’s hard to be nice about the Honda EX7. The Honda EX7 sits somewhere between the Honda EX650 and the Honda EU10i having few of the advantages of the Honda EU10i and none of the inspiring qualities of the Honda EX650.

Honda EX800

They are heavy, old and difficult to source spare parts for. Not many of these about and they are nowhere near as quiet as the Honda EM650 and Honda EX650. However in its favour it does have precise AVR voltage control and shares many parts with the more common Honda EX1000.

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Honda EX1000

Noisier and heavier than the later Honda EU10i and heavy too but hard as nails.

Honda EU10i

Super light weight, pure sine wave inverter with ECO throttle. The Honda EU10i has it all. Or has it.  The GXH50 engine is unlined and, unless 50hr oil changes are very strictly adhered to, fast wearing and uneconomic to repair. The EU10i is the trickiest machine to buy second-hand. So if you want one, buy new.

Kawasaki GA1400A

Heavy and not fantastically quiet but they are are a true 1kw continuous output AVR controlled machine with proper 16amp sockets , 220V and 110V and 12V outputs. The Kawasaki GA1400A is a strong contender for commercial jobs that would destroy the lighter Honda EU10i.

Honda EB1900

Just don’t! Weird discontinued AVR system that cannot be easily repaired.

Honda EU20i

With its tough GX100 engine this is a super little pure sine wave inverter. Of all the suitcase machines I sell the one I worry about the least is the Honda EU20i. Fantastic but pricey.

Honda EU26i

2.4kw continuous from a quiet and compact pure sine wave inverter. The Honda EU26i lacks the wheel kit and electric start of the Honda EU30is but I love the simplicity and easy maintenance of the Honda EU26i. The engine is just the same old GX160 that Honda has been sticking on everything since T.rex bit the dust.

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Honda EU30is

Big brother of the Honda EU26i with wheel kit, electric start and Honda GX200 engine. The Honda EU30is is slightly heavier than the Honda EU26i but with wheels it’s no big deal. Again the Honda EU30is benefits from the ruggedness and easy maintenance of it’s Honda GX200 engine.

Honda EX3000

The Honda EX3000 was a nice simple, quiet, AVR controlled silent runner but heavy and bulky compared to the Honda EU30is.

Stephill SSP3000

Powered by the GX200 6.5hp engine this is a simple and reasonably compact capacitor compensated genny in a wheeled acoustic enclosure with forced air ventilation. Sturdy, quiet and cheap. Worth considering as an alternative to the Honda EU30is and EU26is for LPG conversion.

Honda EX4000s

A simple, quiet and reliable machine with precise AVR voltage control and electric remote starting. Converts to LPG like a duck to water. My top choice for domestic back up power but perhaps a little too big and bulky to win out over the EU30is as a portable generator.

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Honda EU65is

Similar to the EU30is but much more output. The Honda EU65is is the silent version of the Honda EM65is and apart from a few extra sound proofing panels there is not much to tell them apart. The Honda EU65is and the Honda EM65is both use the Honda GX390 single cylinder air cooled engine and benefit from inverter pure sine wave technology, ECO throttle, wheel kit and electric start. At only 99kg they out-maneuver the larger, heavier but infinitely more durable Honda EX5500.

Honda EX5500

The last of the truly commercial grade machines from Honda. Fitted with the water cooled, pressure lubricated, twin cylinder GX360 engine, the EX5500 is a super silent, AVR controlled bruiser designed to work hard day in and day out. Almost all other Honda generators use air cooled splash lubed engines but the EX5500 is in a class of its own.

Honda EX4D

Can’t say I’m keen. Maybe my experiences are not typical but I’ve seen a few with problems relating to the rear main bearings.

Honda EX10D

Amazingly quiet 10kw diesel generator but my reservations about the high service and repair costs of 3000rpm diesels stops me from loving this machine.

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by Peter Noble