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Two Stroke 1kW Generator Test

A few days ago on rec.outdoors.rv-travel (RORT) someone asked about the capacity of my little 2-stroke generator. He also asked how much juice my little electric chainsaw consumes and how well it operates with the generator.

So, dear readers, I decided today to brave the cold winter weather of the mountains here in Tellico Plains (actually I love the weather but this sounds better) to instrument this little combination.

My instrument of choice for this test is the Watts Up Pro ES. [1] This instrument isn’t my normal first choice, that being a Kill-A-Watt [2] but in this case, the cord on the WUP and the display buried inside the case where it works better in the cold won the day. This instrument behaves badly on low power factor [3] loads but the chain saw in question is of fairly high power factor so the meter is fine.

Test Setup [4]Here is the test setup. (click photos to enlarge) On the left is the WUP. In the center is the little $39.00 electric chain saw that I bought several years ago thinking that it would be a one-season-wonder. Several years later it is still running fine. On the right is the UST 1kW generator. It is the same generator sold widely around the net for about $100. For example, Northern Tool [5]. You’ll notice that mine is red while the NT one is blue. That’s cuz the Chicoms will paint it any color you want. I have a NT unit and it is identical in all but cosmetic respects to this one.

Test Plan

The plan was to take three readings,

I used the WUP’s capability to capture peak watts to acquire the data while I was busy operating the saw. I should add that the temperature was 30 degrees and the sea level corrected baro pressure was 30.58, altitude 1950 feet. The cold air should make the generator look good, while the altitude detracts a little and the cold makes the saw draw a little more power. Since I’m not writing a paper to be published in Nature, we won’t try to compute any normalizations.

Idle power

Saw idling [6]Here is the saw idling. Since the saw contains a universal motor and since a universal motor, like all series motors, speed up with lessened loads, it’s not surprising to find the saw running very fast and drawing almost 3/4HP. The generator sounded like it was a bit loaded but not enough to increase the noise any.


Normal Sawing

Routine cutting [7]Here I was sawing normally, cutting through an about 5″ diameter log. I wasn’t being particularly careful about loading, simply sawing like I normally do. The saw is drawing almost exactly 1 hp (that being 746 watts) and the generator sounds fairly heavily loaded.

Highest Load

Maximum Load [8]For this test I located the WUP where I could see it and worked the saw aggressively into the wood until I achieved the maximum wattage I could. The generator was fully loaded and sounded like it had slowed some. Unfortunately this instrument doesn’t easily capture frequency so I don’t know how low. Subjectively, not all that much.

This is about 1.4 electrical horsepower. This tells us several things:

  1. The generator meets its nominal rating of 1kW.
  2. The claims seen in some e-stores that this is a 1200 watt generator are false. The generator was obviously at the higher load that it could support and maintain some semblance of 60 hz output.
  3. It lays to rest some claims that have been made that this generator cannot output a kW.

My homemade electric lawnmower that I also operate from the generator draws a bit more power, judging by how it loads the generator down in heavy grass. The generator has obviously slowed down considerably and the output power is far out of spec. Nonetheless, it operates my mower just fine. Take that, Honda! :-)

I was going to test my mower but for two problems. One, no grass this time of year and two, it’s packed away deeply in my basement and will require a SAR operation come spring. I’ll get back then.

Oh, and before you ask, the reason I use an electric lawn mower with a generator instead of just using a gas lawnmower is simple. The whole electric mower weighs perhaps 20 and no more than 30 lbs. Second, when I’m close enough to the house, which is most of the time,I use shore power. Generator power is strictly for when I’m too far away.

I had planned on operating and instrumenting a 1,000 watt metal-halide light on the generator and document the results but alas, the little generator ran out of gas, my feet were getting cold and more gas was on the other side of my property. We’ll save that one for a later day too.

—— 01/23/2008——

I received a question concerning the model number and nameplate of the Northern Tool generator, the blue one. This is not the generator that I tested but it is in every way identical to the red one except for cosmetics. In response, here is a photograph of the nameplate.

Northern Tool Blue generator nameplate [9]

Yep, Northern highly over-specs this generator. A shame, as it is a competent 1kW generator.

John

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