Portable power-is it just what you need for extra AC power and battery charging needs, and, if so, what size generator do you really need? Well answer those questions and more as we test and evaluate a cross section of generators from the popular makers that range in size from 750 to 2200 VA (volt-amps; we use this instead of watts because, while watts is an accurate measure of a generators ability to handle resistive loads, it doesn’t take into account the power factor of a motor; a typical power factor for a motor is .7, which means it takes about 30% more current to operate than its data plate rating in watts would indicate). We also test a new design for portables called VST or variable speed technology that makes for a lighter and smaller generator than ever before. Well also cover specific evaluation criteria to use in selecting what best suits your needs.
One thing is clear from our testing, and that is you will probably need a larger generator than you think. First, the model designations tend to be misleading if you think they indicate the power available for continuous use, as they only refer to short term-15 minutes or so. For example, the Yamaha EF1000 only has 850 VA available on a continuous basis. Second, these ratings are based on purely resistive loads such as lights or a heater. Heavier loads, such as motors, or anything containing a motor, will significantly lower the effective available power. To cite Yamaha, the manual indicates that it will successfully run motors up to about 290 watts. In practice, we were able to run substantially higher-rated motors. Yamaha apparently chose a worst-case scenario so users would not be surprised if a motor did not run properly.
Unless you happen to be a weight-lifter, you also should plan on a means of moving these units around (with the exception of the Coleman 1000). Even the 850 VA models top 60 lbs. when fueled up.
You will also have to take noise into consideration both for your neighbors and yourself. Portables can be particularly onerous from a noise perspective; unlike larger, installed generators, which have larger mufflers and many of which run at 1800 rpm, these little devils run at 3600 rpm or more. When you look at the listed specifications, the dB (decibel) noise ratings initially don’t seem too obtrusive (64 dB is a common figure). However, many makers base their readings on a distance of 23′. We did our testing at a distance of 10′.
Portables are not a low-price replacement for on-board generators. Nor are they designed for use in an enclosed space, and would quickly fail from overheating-providing they did not start a fire first. Also, there is no provision for venting exhaust, and no safe way to jury-rig a portable one. These units are definitely not designed for a marine environment in terms of corrosion protection, so if you plan to carry one aboard, protect it as best you can. They shouldnt be run very far off horizontal for proper lubrication. Lastly, these units are designed for intermittent service, as opposed to running for hours on end. What are they good for? Powering tools, such as drills and sanders, and yard work where AC power is not readily available.
Variable Speed Technology
There is a new way for the production of AC and DC power in portables. While this design has been around for some time in high-end, fixed generators, Coleman has applied the technology to a portable, its model 1000. Unlike the traditional models, which must maintain 3600 rpm, VST allows for a variable engine speed, allowing the use of smaller, more efficient engines for a given output, with a drastic reduction in weight.
Other VST benefits include huge increases in DC current available for extremely quick battery boosting-70 amps in the Coleman unit vs. 10 to 15 amps for the others.
How We Tested
The first thing we did was to run each generator for at least an hour with variable loads to give the engines a chance to break in. We then applied a number of different loads, both resistive and reactive (motors). We tried to use tools you might want to run such as drills, polishers, heaters, sanders, all the way up to a 14-amp inductive motor with a surge requirement of 40 amps.
We measured and observed waveforms, both with loads (tools doing their jobs) and free running, using a Fluke Model 867 graphical display meter, as well as recording simultaneous voltage and frequency. A Fluke Model 36-amp meter was also attached to the circuit to measure both short term surge and operating current with a load on the tool. We used the same combination of loads on each generator, adding larger loads to the higher- rated generators until they would not run the particular tool. We also tried substantial overloads, for one minute, to see whether the circuit breakers would work.
For battery charging tests, we used a 50% discharged (based on a voltage reading) group 27 starting/deep cycle battery. Because of the very basic battery-charging design of our test generators DC output, we recommend the use of a dedicated battery charger plugged into the AC side of the generator for a proper, safe, and complete charge. Use the higher-powered DC side for boosting and a quick charge of a low or dead battery.
For dB testing, an analog dB meter was used, set to the A weighted, slow-response scale. For reference, every 3-dB increase means the sound is noticeably louder. Ten dB means the sound is doubled.
Coleman Powermate 1000 VST
To achieve its 22-lb. weight, the Powermate 1000 VST has a 49cc two-stroke engine. The use of variable speeds allows such small displacement because it can rev from 3500 to 6000 rpm to keep its power up when loads increase. Two-stroke engines require a premix of gas and oil. There is also the issue of some smoke-its not terrible, but there is the typical smoke of two-strokes. The 1000 is about as loud as the larger Honda, but during high-rpm operation the noise level rises significantly and sounds like a muffled chain saw-not very soothing.
Big load changes cause rapid rpm changes, which can be disconcerting until you realize this is normal. An electrical downside to the rpm changes were significant voltage spikes of well over 200 volts RMS while the generator electronics tried to compensate for these large load changes. We would be reluctant to plug any solid state electronics in without an external line conditioner to put a clamp on voltage spikes, as well as sags. To a lesser degree, the voltage swings were present on all the portables tested.
We found certain light loads on the Coleman 1000 (a 100-watt bulb) caused the generator to hunt back and forth trying to find the right rpm for the load. This caused noticeable changes in intensity of the bulb. General performance was just adequate, in that there was very little surge capability. Our 750-watt heater maxed out the generator, dropping voltage down to a steady 98 volts after a minute-below the acceptable level. To the generators credit, it held very steady in the frequency range.
DC performance is both dramatic and potentially damaging. Its dramatic in the speed with which it works, but the voltage and current is high enough to overheat and literally cook a battery. Monitor the battery carefully, and if the case becomes warm to the touch, disconnect. Coleman calls it a battery booster (not a charger), and that it is. When we attached it to a 50% discharged starting battery, it pumped in 15.7 volts at 37 amps, a fantastic output, bringing it up to a full charge voltage very quickly. Coleman recommends a two-minute boost for an auto-size battery, and we concur. If you want to charge a battery for maximum performance and battery life, use a dedicated charger.
This unit has been around for many years and is well-engineered. It is the lowest power four-stroke in our test, but also the quietest, and notably so. It easily met its ratings, powering two resistive loads totaling 1090 watts, and maintained frequency and voltage to its specifications. When we overloaded it to 1500 watts resistive, the voltage dropped to 80 volts and the unit struggled, but the circuit breaker did not kick in after a minute as it should have, a trait shared by the other units. This means you shouldn’t trust a circuit breaker to tell you when you are overloading the generator.
The Yamaha comes with a DC power cord for battery charging, and its DC output of 14 volts will not cook batteries, but also will not charge them very quickly compared to the Coleman. The power-on pilot light is nice, as is the low-oil light, low-oil shutdown and the built-in funnel for adding oil.
If quiet operation is a real priority, give this one a good look.
Like the Yamaha, this unit has been around for many years and carries a matching two-year warranty. It had the next-best approximation of a sine wave, which probably contributed to its gutsy performance. It easily met all ratings and then some. This robust unit has conservative ratings, as it was the only unit of the three in the 1000-watt range able to start, run, and use our 7.2-amp motor under load.
In our 50% overload test, the circuit breaker should have popped, but like all the other units, the engine kept on trying as the voltage dropped down to 80 volts. In all likelihood, the breakers will work, just not as fast as wed like to see.
This unit has a frequency meter instead of a voltmeter, and its design can be said to be elegantly simple or less flatteringly Mickey Mouse, particularly if you have less than perfect vision. It consists of several tiny, bent pieces of metal cut to vibrate at, above, and below the correct frequency. There is certainly very little to go wrong with such an arrangement, but a voltmeter would have been nice for this more expensive unit. The Honda has a low-oil shutdown, as does the Yamaha.
The Hondas DC battery-charge rating of 8.3 amps is the lowest of the test group.
Coleman Powermate Pulse 1850
This unit can be found in several iterations, depending on the brand of engine used, with some slight variations in listed power output. The model we tested had a Briggs & Stratton engine. The weight of this unit, at around 75 lbs. with fuel, pushes the upper limit of the term portability. It is, however, a good value in dollars/watts,while giving up some amenities and one significant feature (low-oil shutdown). There are no indicators other than a pilot light.
The case is tough poly plastic (not necessarily a bad thing around water). Around the exhaust area there is a metal shroud. Coleman had a good idea in making the spark plug easily accessible through a cutout in the top of the case, as a fouled spark plug is probably one of the most common maintenance problems. The unit was able to meet its 1500 continuous VA rating, powering a 1500-watt heater with nothing to spare. It easily started our larger, 7.8-amp inductive motor, but it performed work at 20% below the house power baseline. The generator seemed to vibrate a bit more than the other models.
The unit comes with a DC cord (complete with storage bag) that plugs into the unit for battery charging. The output of the DC side was 20.5 no-load volts, but dropped to 15.7V at 11.5 amps current on a half-discharged starting battery. This is high voltage and current, and we advise careful monitoring and short duration (just minutes) when boosting batteries to avoid boiling the electrolyte. To Colemans credit, it lists an 800 help line for customers.
At 125 lbs. fueled up, this unit definitely takes two persons to move. The built-in, steel tube cradle, however, makes moving it surprisingly easy, as each person grabs a side and away you go. The Kawasaki was able to easily meet its design output current loads, and was able to successfully start large inductive motor loads. We were able to start and use a 14-amp inductive motor (table saw) with a surge current of 40 amps. Theres an old hot rod saying that theres no substitute for cubic inches, and thats the case here. The larger engine has the extra kick to power up large surge loads. This generator also had the closest approximation of all tested models to a true sine wave, and this also may have contributed to its good performance.
Because there are no shrouds or coverings, access to all maintenance items was easy.
With a 4-gallon tank, it will run for 11 hours at 50% load, far greater than the others in the test. Also, with an overhead-valve engine, it should have greater longevity and service life. The common engine in small generators is a side-valve design, which is not as efficient on gas or oil.
This Kawasaki model is a basic, stripped-down model, with DC battery charging as an option. There were no meters other than the oil alert light and pilot light. This model was the only generator in our test powerful enough for a separate 220-volt plug, so if you are looking for 220 power, this is about as small and simple as there is. Interestingly, the noise level was no greater than the other generators in the test and had a less annoying sound.
The VST Coleman 1000 is a breakthrough model in size and weight. Keep in mind, however, that this model has very little surge capacity for motors. The modified sine wave output and voltage spikes are not as kind to solid state electronics, so a line conditioner should be considered necessary. The chain saw-like noise can be harsh on the ears. Nevertheless, 22 lbs. with a huge battery boost capacity for less than 500 bucks! We expect to see others soon, possibly with four-strokes or super high-power, light alternators.
If it has to be quiet as possible, the Yamaha is your best choice below 1000 VA. The Coleman 1850 offers the most bang for the buck, but buy a fuel strainer. Need the most power for starting small motor loads and reliability? Go with the Honda. Need lots of watts, long run times, and 220VAC power to boot? The Kawasaki is a great choice, but bring a friend to move it around.
Contacts- Coleman Products, 4970 Airport Rd. Kearney, NE 68848; 800/445-1805. Honda of America, 24000 US Route 33, Marysville, OH 43041; 513/642-5000. Kawasaki Motors, 5080 36thSt SE, Grand Rapids, MI 49512; 616/949-6500. Yamaha Motor Corp.; 6555 Katella Ave., Cypress, CA 90630; 714/761-7300.