15" Trimmer 2.5 Ah run time 15 minutes or less

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  • Updated 11 months ago
I purchased the ST1502SF trimmer with the 2.5 Ah battery a couple weeks ago and have been using it to clear grass about 1 foot tall. With regards to the operation of this unit, it easily compares to the Husqvarna brush cutter with a string attachment that I was previously using. The Ego doesn't have as much "power" but it is just as quick to clear tall grass and doesn't get tangled up as much as the Husqvarna - so on that front I am very impressed.

I have been researching this model (and similar competing models) now for the past 2 years and finally decided to go with this one. Based on specifications, reviews, and videos, I had expected to get around 25-30 minutes runtime in tall grass, and this video states "up to 45 minutes of run time" https://www.youtube.com/watch?v=Ag7dHVggxa8. However, I am consistently getting around 15 minutes of run time. I am following the manual for technique for cutting tall grass (i.e. using a sweeping motion and working my way down in several cuts for each section). I have been using straight shaft gas models for the past 15 years so I feel that my technique is ok and shouldn't place any undue stress on the trimmer.

Yesterday I only got 13 minutes before it cut out and the battery light turned red. First I thought maybe there's a overload/thermal cutout due to the tall grass (even though the motor and battery didn't feel hot to touch, only warm), so I waited 10 minutes. I pressed the battery button and it lit up green. It started up again but cut out after about 10 seconds with the red battery light again. I am assuming this means the battery is dead, but after waiting a few minutes the battery button turns green when pressed each time - how accurate is the battery indication light? The battery has been charged several times so it shouldn't be a "battery break-in" issue.

Is 15 minutes an acceptable run time for the 2.5 Ah model in tall grass? If I had known this I probably would have just purchased another gas model. Seems like everybody else on the forum gets 20-30 minutes of runtime so I'm wondering if mine is faulty. Does anybody have any suggestions? Thanks.
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Posted 11 months ago

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Ben Phelps

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Sounds like a battery issue to me. I have the carbon fiber shaft trimmer ST1520S and can edge and trim my 5000 sqf yard 3 times before the 2.5ah battery is dead and needs charging.

I'd contact EGO.
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Tae Cooke

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Here's the thing: There's a major difference between "trimming" and "clearing". Trimming, even at high string speed, doesn't take much energy. Clearing on the other hand, takes a lot. Not to mention that with trimming you typically spend a bunch of time walking around while clearing is full power all the time. The 2.5Ah battery only has 140Wh of energy. If the motor draws 500+W at full load, there's where your ~15 minute runtime comes from.

There was a video by Kite Army clearing a field: he got 9:21. (https://youtu.be/uMxtcx70RMs?t=236)

As for the battery light, the old-style battery with the single illuminated button is pretty INaccurate unless it's in the active tool. Batteries naturally float back up in voltage when not used, and fool the detector circuit into thinking they're ok. If the tool in use shows a red light, you can be sure the battery is just about dead. Overheating would be orange and overloaded would flash orange.

Unfortunately it sounds like this tool isn't ideal for your use case unless you get multiple / bigger batteries, or relax for the hour it takes to slow charge on the included charger.
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That runtime sounds about right for heavy use. (A single 2.5 AH battery lasts me about 10-15 minutes in the power head with cultivator attachment.)  So the battery and trimmer are probably working correctly, but it sounds like you need more (or a larger 5.0 AH) batteries to do what you want to do with it for as long as you want to do it.  It's hard to beat gasoline for energy density / runtime, but for easy start/stop and no-mess no-fuss electric is the way to go. Ego tools have comparable power to gasoline models, but the energy density of liion batteries are nowhere near that of liquid petroleum fuel.
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szwoopp, Champion

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and nothing more enjoyable than holding an internal combustion engine in your hands just two feet away from your face :)
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Ken, Champion

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Depleted batteries can have their charges rebound slightly after they sit for a few minutes, but as you're experiencing, it's not enough to add any meaningful runtime. The battery simply needs to be recharged. That'll take about 50 minutes for your 2.5 Ah battery on the standard charger.

As others have said, the runtime seems reasonable, given the nature of the work you're doing with the trimmer, especially if you're running it at full speed or close to it.

The 2.5 Ah battery lasts me a lot longer with "normal" weed trimming around my yard because i rarely have to run it at higher speeds.
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William E Hanson

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A 2.5 Ah battery under extreme use wouldn't get but about 15 mins. I use that on my blower primarily on hard surfaces, then swap in a 5.0 Ah when I need turbo for blowing leaves needing longer run times.