I wanted to replace my Homelite 14" dual-line string trimmer as I finally had enough of the noise, pollution, starting issues, mixing/storing of gas & oil, engine maintenance, and the constant need (and effort) to replace the pre-cut line strips.
Cordless is the way to go. However, given the current limitations of battery technology, I was concerned about finding a string trimmer that had the necessary balance of power, run time, weight, and charge time. I also wanted a reliable unit that would give me years of trouble-free service.
I did my usual due-diligence, and spent hours reading reviews and handling a few units at the local hardware stores. I work in the computer/electronics field, so I am very familiar with battery technology and the other parts of a string trimmer. I know I wanted Lithium Ion batteries with >30 minutes run time. I was also more interested in the highest AH (Amp Hour) rating than Volts (e.g., 18V, 20V, 36V, etc). Marketing is pushing the voltage rating (largely because the lower-cost Ni-cad batteries have a lower Amp-Hour rating in comparison to Lithium Ion batteries of the same weight). However, voltage is a poor indicator of how powerful and long the trimmer will run. For example; both a tiny hearing-aid battery and D-size flashlight battery have the same voltage rating (1.5V), however the D-size battery has a much higher Amp-Hour rating. If you replaced the D cell in a flash light with the tiny hearing-aid battery, the light would barely be visible and would drain the battery in less than a minute. Whereas the D cell would light the lamp at full brightness for over 30 minutes. Same basic principle applies to a trimmer. Choices as of now (2010) for Li-Ion batteries range from 1.3 Ah to 6.0 Ah. 6 Ah is a huge amount of capacity! 1.3 Ah is small, and given the amount of current (Amps) required each minute to spin a string-trimmer motor powerful enough to cut grass, is only suitable for a postage-stamp sized yards.
For comparison; as of 2011, a hi-capacity laptop Li-Ion battery is ~ 4.5 Ah.
In addition, Li-Ion batteries do not have the memory effect that NiCad batteries do, so I do not have to totally discharge the battery before recharging. That is a major weakness for Ni-Cads because you always end up charging the battery for the full 12+ hours before each use. Furthermore, Li-Ion batteries hold their charge over a much longer period of time than a Ni-Cad. I can fully charge a Li-Ion battery and, a week or so later, top it off with a quick charge (say 90 minutes) as required over the season.
Unfortunately high Amp-Hour Li-Ion string-trimmer choices are very limited at this time. The Greenworks 21602 and Troy-Bilt TB57 are really the only choices; the TB57 being the cheaper of the two. They are basically the same unit. They both use the identical Li-Ion 6AH battery and 4 ½ hr. charger. The only real difference (other than color) is the shaft, throttle switch, and the swivel hinge for edging on the Greenworks. BTW: you could buy the TB57 and use the battery on the Greenworks leaf blower. I handled the TB57 at Lowes, and I agree with the negative reviews about the short shaft and force required to hold the safety switch in.
In the end, I ordered the Greenworks mainly because I am 6' tall and the TB57 was just a little short (even with the telescopic shaft at maximum) and I know my finger would get numb from holding the power switch down.
I really struggled with the decision to buy this particular brand of string trimmer. I was hesitant to buy an unknown brand; especially since the Greenworks web site did not list any near-by service locations to drop the unit off for warranty repair (only option is mail in), and reading two reviews on Amazon where the warranty hot line was non-existent or unresponsive. That makes Greenwork's four-year warranty worthless. I am also concerned about the longevity of the electric motor. Will it last +5 years? I noticed two people already experienced early-life motor failures (one Greenworks and one Troy Bilt). I plan on giving the Greenworks a good workout and return it to Amazon if I find anything I don't like during the first 30 days.
Well I got the Greenworks four days after ordering it (selected the free shipping option) from Amazon (exceeding my expectation and one of the main reasons why I buy from Amazon).
Assembly was very easy (needed a Philips screw driver for the one screw). Build quality seems good. I do agree with one reviewer that the plastic handle feels a little cheap as it flexes a bit. However, that flex does make the unit even more comfortable. The shaft is long enough for me. The balance and weight are very good.
Regarding cutting power; this is not a commercial grade trimmer that you use for a landscaping business. The power is sufficient to cut through dense grass; however I have to move a little slower than I did with my gas trimmer. This trimmer is suited for yards that have been maintained well in the past. I would not recommend it for a yard that is, or often becomes, overgrown (i.e., grass or weeds over 12" tall).
The automatic line feed works very well. Each time I start the unit it feeds ¼" of new line. The only drawback is that I go through a lot of line when I move from tree to tree; stopping the unit each time to save battery power. The four hour charge time is adequate as it does keep me from missing a scheduled grass cutting if I forget to charge the battery the day before (can't do that with a 12 hr. Ni-cad charger). Like any battery powered trimmer, the noise level is very low. I am now able to trim the yard in the early morning (before I start using the lawn mower) without getting my neighbors upset. So far I am satisfied with this purchase.
However, I did notice the motor slow down to about 1/3 the speed while using it. The speed returned to normal when I released the throttle and pressed it in again. This happened three times already. I am not sure if the motor has a built in thermal power reduction (which is good as it would prevent the motor from burning up). If it starts to happen more often, I will return the trimmer to Amazon.
Update week 1:
Battery life is excellent. I have used this trimmer over a five day period on the original charge. After +30 minutes of use, I still have three of four battery status lights on.
I have noticed that the motor air vents clog with grass clippings after a few minutes of use. This may contribute to the motor overheating/failure problems some are experiencing. I now make it a practice to clean the air vents (wipe off the external grass and blow out the grass inside the motor) every few minutes. I think Greenworks should design a thick foam ring that fits over the motor to trap the clippings. Then all I would need to do is periodically rinse the foam ring in soapy water.
Update week 3:
After 3 weeks of use, I am very pleased with this trimmer. It took awhile to get use to the fact that it is always ready to go with just a push of a button; no need to charge before each use, no worries bout prepping the motor and trying to start it, etc. I now find myself pulling out the trimmer when I come from work and spot a few weeds while walking along the driveway or sidewalk. The battery status bar finally dropped down to 2 of 4 lights; so I charged it up to give the battery charger one more test before the 30 day exchange period with Amazon ends.
I have not experienced any more slow downs. I suspect that was caused by clogged air vents.
I used the edger for the first time last week; just pushed the big button on the shaft near the motor and the shaft pivots 90 degrees. The wheel rolled smoothly and the angle of the shaft was perfect as it gave me a good view of the cut. It was much easier than I thought and produced consistent results; far better than the free-hand edging method I have been using for years.
I have already used all the string on the one spool and inserted the free second spool (BTW - easy to change). I went to Home Depot and purchased a 300' re-fill package of the .65 blue line to re-fill the spools as needed. For ~ $7, I have enough line for years.
However, the real shining star is not the trimmer, but the 6AH Lithium-Ion battery. The capacity is perfect for all but mega-size yards.
I received the Greenworks 24602 blower for Father's Day; it uses the 20V/6AH Li-Ion battery from the trimmer. Now I can trim the yard and use the blower to clear off the grass clippings from the driveway and sidewalks. The blower with this battery makes it very convenient to use and makes it more versatile. For example, I used it to blow dry my car after I washed it (beats ringing out drying clothes). I also opened the car doors and blew out some dog hair and dust from inside the car.
I would buy the Greenworks chainsaw (also uses the same battery) to cut up the many small limbs that blow down after a storm. Unfortunately, the current $69 10-inch chainsaw is too expensive and large for what I need. A 6-8 inch model (with a lower cost) would be ideal to cut up limbs and small tree shoots into small enough pieces to toss them in a trash can.
Bottom line: "It's the battery stupid" (I think that's a Bill Clinton quote); the fully capable string trimmers (either the Greenworks or Troy-Bilt) and leaf blower only exist because of it. Greenworks 21602 20-Volt Lithium Ion 12-Inch Cordless Electric String Trimmer/Edger with 6 Amp/Hour Extended Run-Time Lithium Ion Battery & Charger - Lithium-ion - Weed Whacker - Cordless Trimmer - Trimmer'
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