How Long Do Cordless String Trimmer Batteries Last?

Two kinds of battery life

People ask this question in two ways. One is how long a battery runs on a single charge. The other is how many seasons the battery lasts before it needs replacing. They have different answers, so it helps to keep them apart.

Runtime per charge depends on the pack's stored energy, the trimmer's motor, the line thickness and the grass you are cutting. Total lifespan depends on how the pack is charged, stored and used over time.

What published runtimes look like

Runtime claims vary a lot. Among the 15 products on our best cordless string trimmer page, only three list a runtime at all. The longest listed figure is 63 minutes. The EGO POWER+ ST1502SA lists up to 45 minutes on its included 2.5Ah battery. That pack is rated at 140 Wh, and the charger listed with it refills the pack in 50 minutes.

Smaller 20V to 24V kits sit at the other end. The HortiHub lists about 15 to 20 minutes of runtime per charge from its two 2.0Ah batteries. The goodjob 20V lists 40 to 60 minutes of continuous runtime with its two 2.0Ah batteries, and says this varies by load. That figure covers both packs used one after the other, so it is not a single-charge number.

These are maker claims taken from listings, and we compare published specifications rather than running our own runtime tests. Treat them as a guide, not a promise.

Use Wh to compare models fairly

Voltage alone does not tell you how long a trimmer will run. Battery energy in Wh combines voltage and capacity (Ah), so it shows how much charge the pack actually holds. The math is simple: volts times amp hours equals watt hours. For example, 56 V times 2.5Ah gives the EGO's 140 Wh.

Higher Wh generally means longer work between charges, though a more powerful motor will use that energy faster. If you want a deeper comparison, our best cordless string trimmer page lists Wh next to weight and cutting swath, so you can see the tradeoffs.

Listed battery specs at a glance

The table below uses only figures from the product data on our comparison page. A dash means the maker did not list that number.

What shortens runtime on the job

Even a large pack drains faster under heavy work. A few things make the biggest difference:

• Thick, tall or wet grass makes the motor work harder than light trimming.
• Thicker line, like the EGO's 0.095 in, cuts tougher weeds but asks more of the battery than 0.065 in line.
• A wider cutting swath means more material is cut with each pass.
• Running at full speed all the time. Models with variable speed let you save charge on light jobs.
• Cold weather, which can reduce how much charge a lithium-ion pack delivers.

How to make the battery last more seasons

Lithium-ion packs age with every charge cycle, and heat is their enemy. You cannot stop wear, but you can slow it. Follow these steps:

1. Use only the charger made for your pack, and never charge a damaged or swollen battery.

2. Let a hot pack cool before charging it, and charge in a dry spot away from direct sun.

3. Store the battery indoors in a cool, dry place, not in a hot shed or car.

4. Avoid draining it to zero over and over when you can swap in a second pack.

5. For winter storage, leave the pack partly charged rather than empty or completely full, as most makers advise.

Always check your manual, since each brand has its own storage and charging rules.

Picking enough battery for your yard

Think about how long your usual job takes. A small patio edge might need only a short session, while a long fence line can take much more. If your yard is bigger than one pack can handle, a second battery is the simplest fix. Kits like the goodjob and HortiHub each include two batteries, and the ALSO GO kit lists two 4.0Ah packs.

Weight matters too, because bigger packs often come with heavier tools. Among models that list weight, our page shows a range from 3.28 lb to 7.8 lb, and the 7.4 lb EGO carries the 140 Wh pack. Our cordless trimmer comparison helps you balance runtime against how tiring the tool feels.

Also check whether the battery and charger come in the box. The SHOHO model on our page leaves them out, so it only makes sense if you already own compatible packs.

Safety notes

Wear eye protection every time you trim, since line can throw stones and debris. Some kits include goggles, but check that they fit well. Remove the battery before changing line, clearing a jam or adjusting the head, so the trimmer cannot start by accident.

Keep batteries away from water, metal objects and open flame. If a pack gets very hot, smells odd or changes shape, stop using it and follow your maker's disposal advice. Do not throw lithium-ion batteries in household trash.

Frequently asked questions

Can I use a bigger battery on my trimmer?

Only if the maker says it is compatible. Packs must match the tool's voltage and connector. Using the wrong pack can damage the tool or create a safety risk.

Does a second battery double my work time?

Roughly, yes, because you swap packs and keep going. You still need time to recharge the first one, so charger speed matters if you want to work without a long wait.

Why does my trimmer seem to run out sooner than the listing says?

Listed runtimes are often for light, steady use. Heavy weeds, thick line, high speed and an aging pack all cut the time you actually get.

Are older cordless trimmer batteries still worth using?

It depends on the pack's condition. If it holds a charge long enough for your jobs and shows no swelling or damage, it can keep working. Otherwise, check whether the maker still sells a matching replacement.