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Kobalt 40-volt Max 15-in Straight Cordless String Trimmer (Tool Only)

20 Reviews
  • 40V gear reduced string trimmer with 2.5Ah battery gives you the power you need for yards up to 1/2 acre (battery sold separately)
  • Premium heavy-duty 0.080-in dual line feeds through a bump head, making it easy to power through tough grass and weeds
  • Adjustable cutting swath from 13-inch to 15-inch to allow for extended runtime or faster trimming


  • 40V gear reduced string trimmer with 2.5Ah battery gives you the power you need for yards up to 1/2 acre (battery sold separately)
  • Premium heavy-duty 0.080-in dual line feeds through a bump head, making it easy to power through tough grass and weeds
  • Adjustable cutting swath from 13-inch to 15-inch to allow for extended runtime or faster trimming
  • Easy to start variable speed trigger with two-speed settings offer complete control
  • Compatible with Kobalt 40-Volt max family of products
  • Battery and charger sold separately
  • 5 Year limited tool warranty
Weight 8 lbs
Dimensions 38.58 × 10.24 × 6.3 in

Latest reviews

  1. Matwat

    I used this 40v max for a good hr and a half to redo my flower beds and around the house to dig a weed barrier around so weeds won’t grow and man did it work well great battery life and never lost its power performance , I’m in transition of going to 40v max outdoor equipment from gas power and I’m happy with the results of power and how light weight the unit is. I highly recommend this trimmer for power performance and balance of weight distribution!

  2. Long-Ranger

    This is an upgrade to the Kobalt 40 Volt String Trimmer from the model that I bought 5 years ago that still works fine.

    Packaging was good with no damage. The only tool needed to assemble the unit was an allen wrench that was included. Assembly was easy and only took a few minutes.

    Warranty on the unit is 5 years and warranty on the battery is 3 years. I have had some batteries 5 years and they still work and recharge fine.

    It has several new features:
    1. More power and run time while using the same 40 Volt Lithium Ion battery.
    2. New “drop in” battery charger that has a smaller footprint.
    3. 2 Speed gear-driven motor selectable on the shaft with a switch.
    4. Variable speed trigger switch.
    5. Ability to use .080 string as well as .065 string.
    6. The cutting diameter was increased from 12 inches to 13 inches or 15 inches depending on where the string cutter is set. Setting the string length for 13 inches offers more run time than the 15-inch setting which allow for more cutting area if run time is not a concern.
    7. Eliminated automatic string advance each time the motor is started and replaces this with a “bump button” to advance string as needed.
    8. Eliminated the need for replacement spools and rewinding spools (This is a BIG PLUS for me!). Once the spool is aligned, the string is pushed through so that equal amounts are on each side. Then turn the wind button and the string is automatically wound into the spool.

    The battery end of the trimmer is redesigned and the overall length is about 4 inches longer up to 68 inches overall. In addition, it seems to be slightly heavier but still easy to swing.

    Trimming and edging were easy. Advancing the string with a bump work very nicely.

    The only major complaint that I have is that the forward handle has to be adjusted for holding when changing from trimming to edging. The previous model had a handle with “loops” on both sides to easily flip the trimmer over for edging without adjusting the handle. The only other slightly negative comment is that I think that some sort of shoulder strap would make the trimmer easier to use for longer periods.

    Overall, this is a nice trimmer. It is not a brush trimmer but it is very effective on grass (I use it on tall grass and weeds too) and also for trimming. I have been using the 40-volt set of Kobalt garden tools for 5 years now and this is a welcome upgrade even though all of my tools and batteries still work fine.

  3. Theldara

    Product works fine. Only complaint I have is it is a bump head feed, but that is to be expected on an electric. Assembly was simple, all that was needed was the included allen wrench. The trimmer feels sturdy and is easy to use. The battery has a status button which shows the charge level. The metal guide can be moved up, if not needed. Having two speeds is nice, but I’m not certain how much I will use the lower speed. The top lever on the handle has to be engaged in order for the motor to engage, and the bottom lever controls engaging the motor.

  4. Has

    This Kobalt trimmer 40v max is good for smaller yards and small jobs its very light not heavy, easy assembly out off box used it couple time around my house has 2 speeds lower speed and fast speed battery hold up very good 30 min easy working with it , like i said for small yards and around the house can’t beat it lithium ion battery charges fast I would recommend it 5year warranty on the trimmer 3 year warranty on battery it’s a good deal.

  5. PJOKC

    The trimmer was easy to assemble. I wasn’t sure about the strength of the grass shield, but it seems to serve the purpose. The trimmer is powerful. I tried it out on some weeds – no problem. Before writing this review, I wanted to try it out by edging the driveway. The trimmer did the job without effort. Checking the battery, their was still 1/4 of a charge. I am so pleased with the battery powered trimmer. In the past I’ve had to deal with extension cords which had a limited reach. It’s also a bonus that it’s quiet. The battery recharges quickly.

  6. Joey

    The 40 volt Kobalt string trimmer is great. The high speed is good for cutting ping the tuff weeds and the slower speed is good around trees. The trimmer is light to carry and well balanced. The book says the battery will last for 40 minutes. I was trimming monkey grass with it and it lasted a little over 40 minutes. This trimmer is great for grass and normal yard trimming. It will do some of the heavier stuff, but is a little slow on it. This will be ideal for someone who doesn’t want to mess with oil and gas.

  7. Lagtime

    Like so many I have been frustrated for years with a gas string trimmer.. I bought expensive ones cheap ones and within a year they stopped starting. Most recent one lasted 3 months. My yard is too big for an electric and no power. After extensive research I bought this string trimmer yesterday powered it up and used it today. Hallelujah it took me 10 minutes to put together trimmed for about 30 minutes and had 2 lights left. Cut both small and thick weeds and it took them down easily. Oh and its quiet as well.. I’ve only given 1 other 5 in my life. If you are tired of the gas ones like me this is for you.
    The only slight negative is its a little head heavy but not bad.

  8. dave

    I bought the weed eater , blower combo today , charged the battery up go and use the trimmer for about a half an hour and boom …. the black casing around the bump stop explodes , junk

  9. lawndad

    This is the second 40v Kobalt string trimmer I have owned. I purchased one two years ago, and the eyelets in the string head wore through after very light duty work. I was pleased with owning a battery trimmer, and I thought this was a one-off issue.

    I purchased this newer version so I could use the same battery and use the old trimmer for parts. To assemble the front handle, a fastening knob pulls a bolt through a plastic handle. Unfortunately, with very little effort, when tightening the bolt, the bolt’s seat in the plastic handle stripped. I cannot tighten the bolt, cannot assemble the handle, and cannot use the trimmer.

    If the handle assembly were thought through at all, this part would not have been designed this way. Please consider this a general take on what is likely pretty terrible overall build quality.

    I will frustratingly be returning mine to .

  10. Renlaff

    Took my first one back because the bump knob didn’t seem to work. I’d have to push it in with my hand and pull line out manually. Thinking it was defective, I replaced it with a brand new unit. Same issue. I’ll be taking that back today and then gambling with a knock-off replacement battery for my ancient trimmer/edger from Worx. It cuts much better than the Kobalt.
    It’s a shame because I have the 40v Kobalt lawn mower, leaf blower and hedge trimmer. Those are fantastic. But the lawn trimmer (weed wacker) falls way short of the Kobalt standard.

  11. azgeezer

    Start off with a big thanks to E Chandler AZ . at the first of April 2020 I had an issue with the older model of this trimmer and even though had not started curb side pick up the associate took the time to do everything on the phone to replace it with the newer model and even brought it outside for me when I arrived. The new model allows very precise control of the speed. The edge guard no longer has to be removed and reinstalled just flipped up or down as needed. And the installation of new trimmer line is a breeze. As with the older model the battery life between charges is more than adequate. .

  12. DOUG

    I was a little skeptical about an electric trimmer. I was in the market for a gasoline powered one to deliver more strength than the current electric one that I was accustomed to. This 40v trimmer by Kobalt delivered a lot more power than I was expecting. It would be given 5 stars had it not been so heavy – it took awhile to get used to and understand the weight distribution. Also, changing out the line, was not as easy as I expected it to be. it wasn’t too confusing but it definitely was not something that I could do on a whim. Overall, I think it’s worth the hassles it has. Good power, easy to change the battery, and relatively low power usage.

  13. dra

    Like all Kobalt products this 15” trimmer does a great job. Being 40 volt battery it is super quiet while being real strong. Has two speeds. Low and high. Real good charger with indicator lights. It will get a workout this summer. It’s not heavy and It’s well balanced.

  14. Rick

    Whole. Black bump part broke . And no replacement parts. Last me 1 year.

  15. FormerRegularCustomer

    Product worked fine until it failed. Tried to return/exchange it under warranty, which is clearly stated in the owner’s manual. Multiple trips to the store and multiple calls to Kobalt and I still don’t have a replacement. Each one ( and Kobalt) says it’s the other that need to process it. I eventually realized it was not worth the trouble. I have spent many thousands at since buying my house nearby, but I will no longer buy anything that I will have to worry about bringing back under warranty.

  16. Doug

    Bought this trimmer 3 months ago. Works like a beast. Trimming and edging is easy and well done. However, respooling this thing is a major pain in the butt. Following the instructions is useless. The manual says turn the bump knob counterclockwise to respool. Kobalt’s response to another review said to turn the bump knob clockwise. Now which is it? I finally just removed the spool and hand wound it to refill the line and then replaced it back in the trimmer. The advertised “easy to respool” is not true. Not looking forward to having respool in the future. Can only give a 3 star rating for this reason

  17. ElectricBlue23

    Impressed with the easy assembly and overall lightweight. Although the battery appears very big, it weighs nothing. Trim line is easy to advance and the battery was quick to charge .

  18. bandj

    First I want to say that I really appreciated that this string trimmer was charged and ready to be used right out of the box. I was fast and easy to assemble and is light weight. It cut equally as well at both speeds (on what I was cutting). I like having the 2 speed options as I would imagine that it will help conserve battery and provide better cutting control. If I had to make a suggested improvement it would be to add a shoulder strap when the trimmer will be used for extended periods. I do consider this to be a light weight device — so the strap is not crucial – but again why work harder if you don’t have to. All in all very pleased with the performance of this item.

  19. AppleGuy7

    I have to say that this trimmer is an absolute nightmare! The automatic line feed wastes considerable about of line and causes the line to tangle into knots so that you have to cut it with wire cutters.I wasted the entire line cartridge on my first attempt to trim a small lawn. The excessive weight of the battery throws the whole balance of the the trimmer way off and makes it a burden to carry. The worst thing is the replacement process of the line. it is an absolute joke. Cobalt wants you to purchase their 3 pack of pre-wound line cartridges for $20. That’s when I decided to return this pathetic trimmer to . Shame on you Kobalt for manufacturing such a poorly designed trimmer.

  20. flyguy

    Kobalt 40V Lithium-Ion Brushed String Trimmer
    Model KST2540-06

    The unit was packaged in heavy corrugated cardboard container and was well protected as shown in accompanying photo. Trimmer was easy to assemble and was accomplished using included hex wrench in about 20 minutes. Assembly involves putting two halves of tube together,tightening the hex screw and attaching the shield to the motor unit and tightening two hex screws. Fully assembled unit shown in photo 2. The battery needs to be charged prior to first use and a full charge may require from 12 to 20 hours.

    I found the trimmer well balanced and easy to find a comfortable trimming position. I am 6’4″ and stooping for any length of time results in significant back pain. The (no tool required) adjustable lower handle allowed me to find a comfortable trimming position without having to bend my legs or bend over. Once you find a comfortable position for the lower handle I would mark it on the tube for future reference!

    The trimmer comes with rechargeable lithium-ion battery and charger. The battery has a button on top that when pushed provides battery charge status from 10% to fully charged. The charger also has a dual color light; green to indicate whether battery is charging, fully charged or red to indicate over temp or a fault. The battery and charger have a 3 year limited warranty.

    The trim head has dual trimming strings and an adjustable cutting area of either 13 or 15 inches, large enough to take care of trimming and edging most yards. Replacing the cutting line appears straight forward using standard 2.0 mm nylon line.

    I found the trimmer to be well balanced, easy to maneuver and the 40 amp battery provides ample power for trimming most grass, weeds and other growth you might encounter in a residential yard. I am unable to give an estimate of run time of the battery before needing a recharge but in the multiple times I have used the trimmer thus far there has been no indication of loss of power. This battery powered unit is a great choice for replacing your dead or dying gasoline model and eliminates the messy, smelly and somewhat dangerous mixing, storage and use of gasoline. If you are like me and had been relying on a electric model this will eliminated the need for that long extension cord that always comes unplugged as you reach that far corner of the yard!

    In short, I believe this trimmer would be a welcome addition to most homeowners yard tool collection. It is easy to store, light enough for your teen to use, and comes with a 5 year limited warranty to original purchaser.

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