Battery-powered string trimmer purchasing advice: how to choose the right product

  • The most important facts in brief
  • Cordless lawn trimmers are used to work on hard-to-reach areas in the garden
  • Cordless lawn trimmers have either a cutting blade or a cutting string
  • The engine power of most machines is too weak for hard undergrowth
  • In any case, a device with a replaceable battery should be purchased.

What is a cordless lawn trimmer?

In every garden, there are places that are difficult for classic lawn mowers to reach. In their case, battery-powered lawn trimmers provide valuable services. There is a wide range of cordless lawn trimmers on the market, which differ considerably in price and performance. This guide will help you find the right cordless lawn trimmer for you.

A cordless lawn trimmer is often used for the edges of flower beds or for wild growth along fences. Because it does not have a power cable, users are not restricted in their freedom of movement. However, the user has to recharge the battery again and again. Therefore, these devices are not always the best solution for large gardens.

Cordless lawn trimmer in tall grass

How does a cordless lawn trimmer work?

A cordless lawn trimmer essentially consists of six components:

  • Battery
  • Motor
  • Control panel to be able to make settings
  • Cutting tool
  • Telescopic rod for transport
  • Collection container

Visually, cordless lawn trimmers are very reminiscent of cordless hoovers. At the very bottom is the cutting tool, which is directly connected to the collection container. This is where the trimmer collects the cut plant residues. At the top is the trimmer’s control panel and the battery. High-quality trimmers offer different gears. This is very useful because, for example, lawns can be trimmed with much less effort than bushes. The motor draws its power directly from the battery.

These are the benefits of cordless lawn trimmers

The most important advantage that comes with working with a cordless lawn trimmer is the freedom of movement. The device is not restricted by any cable length. In addition, it is comparatively light and can therefore be easily carried from one corner of the garden to another. But there are also other advantages:

Precise work: Because cordless lawn trimmers are relatively light, they are not difficult to handle. It is possible to work quickly and precisely.

Noise: Because electric motors are used, the trimmers make much less noise than mowers with petrol engines.

Health and environmental friendliness: cordless lawn trimmers do not emit harmful exhaust gases.

Cheaper to maintain: The trimmer only draws as much power as it absolutely needs for the battery. Models with a power cable constantly draw full power during use. Mowers with petrol engines require expensive fuel.

Little noise: an often underestimated advantage

In fact, battery-powered lawn trimmers are so much quieter compared to other mowers that they are allowed to be used for much longer. In some municipalities, it is even permitted to use them until 10 p.m., i.e. until the legal quiet period begins. People who live in a densely populated neighbourhood and do not want to annoy their fellow citizens with noise pollution therefore particularly benefit from these devices.

These disadvantages should be noted

Battery-powered lawn trimmers also have disadvantages:

Running time and range: The battery running time is not sufficient for very large lawns.

Power: To prevent the batteries from discharging too quickly, the motors in the trimmers are comparatively weak. They are not suitable for hard undergrowth such as roots made of wood.

Defects: The battery means that there is a component in the trimmers that will eventually fail. Lawn trimmers with a power cable or mowers with a petrol engine last longer.

Comfort of use: Even the longest cordless lawn trimmers are too short for tall users. This means that they have to mow slightly bent over. This is strenuous and can cause back pain. However, there is a certain “training effect”: as with weight training, the body eventually gets used to the strain. The problem becomes smaller over time.

What types of cordless lawn trimmers are there?

Basically, cordless lawn trimmers can be distinguished in two ways: by the cutting tool used and by the presence of a carrying bag.

The possible cutting tools

Cordless lawn trimmers come with plastic blades or a cutting string as the cutting tool. The blades have the advantages that they are somewhat cheaper and easier to change. However, they are also more prone to wear and offer less satisfactory results. Various tests have shown that models with plastic knives deliver only a moderate result: Even after moving back and forth over one and the same area several times, the corresponding area remains stubby in some cases. Trimming with a thread offers better results.

The plastic knives also showed considerable abrasion in the tests. Their mass decreased by 25 to 50 percent after an average long use. Worn plastic elements lay on the lawn after operation. This is not desirable. For pet owners it can even be a problem: cats occasionally eat grass and could inadvertently ingest the plastic. The same danger exists for dogs.

The thread, on the other hand, showed hardly any wear. The abrasion of a mowing unit is so low that it can be neglected. In the medium and long term, models with thread are therefore even cheaper. Users should therefore opt for the threads as a cutting tool, despite the higher purchase costs and the somewhat more difficult replacement.

The advantages and disadvantages of the mowing threads at a glance:

  • Very good trimming result
  • Hardly any wear
  • Low abrasion
  • Higher acquisition costs

Brush cutter or classic cordless lawn trimmer?

To counteract the problem that many cordless lawn trimmers are too short for tall users, the so-called brush cutter was developed as an alternative. Professional gardeners work with these. It is regularly used for the maintenance of parks and public paths. For example, gardeners are often seen mowing along motorways.

Brushcutters are considerably longer than classic cordless lawn trimmers. They therefore weigh more, but have a special carrying backpack. Despite the higher weight, it is therefore more comfortable to work with the brush cutter. It also has a longer battery life and a more powerful engine. It owes its name to these advantages: Users have much greater freedom when working.

Of course, this has its price, and in this case that is to be understood literally. Brushcutters are considerably more expensive than ordinary cordless lawn trimmers. If you only have a small to medium-sized garden, you should not go for a brush cutter for reasons of price and performance. The usual battery-powered lawn trimmers perform sufficiently well. Only in large gardens is it worth considering the top-of-the-line devices.

What should I look for when buying a battery-powered lawn trimmer?

When buying a battery-powered lawn trimmer, there are various aspects to look out for. We explain and provide an overview:

Battery type

Basically, there are two different types of batteries used in lawn trimmers: lithium-ion and nickel-cadmium batteries. Although they are somewhat more expensive, users should always opt for lithium-ion batteries. These have a whole range of advantages over the alternative:

  • They are lighter, which means that the overall weight of the trimmer is less.
  • They have no memory effect: the device will not be damaged if the battery is not fully charged. The same applies if the user does not fully discharge the battery before recharging it.
  • They are smaller: a lithium-ion battery that is the same size as a nickel-cadmium battery therefore lasts much longer.
  • There is only a very low self-discharge: lithium-ion batteries only discharge by one to two percent per month when the device is not in use. The lawn trimmer can therefore be stored for months without power supply and is still ready for immediate use.
  • The toxic and extremely environmentally harmful metal cadmium is not preserved. In 2009, German lawmakers even banned most rechargeable batteries that contain it. The only exceptions are batteries in mobile power tools such as cordless lawn trimmers or cordless drill and screwdrivers.

Apart from the price, the nickel-cadium battery has only one advantage over a lithium-ion battery. It is more robust. This means that it has a slightly longer life span.

The service life of rechargeable batteries

Lithium-ion batteries have a service life of 500 to 800 cycles. This value corresponds to a period of ten to fifteen years with normal, non-commercial use. Nickel-cadmium batteries have 800 to 1500 cycles. They thus offer a service life of more than 15 years. The nickel-metal hydride battery, which is now rarely used in lawn trimmers, achieves 350 to 500 cycles. This corresponds to a service life of seven to ten years. Since an average lithium-ion battery works for at least a whole decade, its disadvantage compared to the nickel-cadmium battery in terms of service life is negligible.

The running time of the battery-powered lawn trimmer

The battery runtimes of cordless lawn trimmers vary greatly. Most models last between 30 and 60 minutes. 30 minutes is usually enough for most users who have a small or medium-sized garden. 60 minutes is more than necessary for most home gardening. Tools with batteries that last an hour are mainly intended for commercial gardeners.

The engine power

The motor power of most cordless lawn trimmers ranges from 450 to 650 watts. The voltage of the battery starts at 10.8 volts for the weakest models and reaches up to 24 volts for more powerful devices. The following should be considered with regard to the motor power: No current battery-powered lawn trimmer (apart from brush cutters) is strong enough for hard grasses, roots reaching out of the ground and overgrown bushes. If you want to trim such vegetation, you have to choose a powerful motorised model that does not work with a battery.

The more power, the better: 450 watts of motor power are comparatively weak. Such trimmers are really only capable of cutting grass without any problems. If money is not the most important factor in the purchase decision, the rule is: the more power the cordless lawn trimmer has, the better it is.

Extendable telescopic arm

Most cordless lawn trimmers come with an extendable telescopic arm. However, the lengths differ considerably. Many inexpensive models, for example, only reach 95 centimetres, which is clearly too short for most users. Good cordless lawn trimmers reach 120 centimetres. Especially tall prospective buyers should take this factor into account.

The weight

On average, cordless lawn trimmers (apart from brush cutters) weigh between two and three kilogrammes. The models of the well-known brands that regularly receive the best customer reviews on the Internet on the large shopping exchanges weigh between 2.4 and 2.7 kilograms. This weight range seems to be optimal for handling the trimmer.

The material of the thread

The threads are each made of different synthetic materials. Nylon enjoys a particularly good reputation. The material is robust and can be produced with a very narrow diameter. Nylon is resistant and razor-sharp. At the same time, the material can be cut without any problems. This is useful when the thread needs to be shortened or replaced completely. Nylon is therefore the best possible material for the mowing thread.

Width of the crop guard

Most cordless lawn trimmers have a plant guard. This is a roll bar that runs along the side of the cutting tool. The name itself explains what it is for: it forms a guard between the plants to be trimmed and those that are to be left standing.

However, there is one problem that applies to all brands: the diameter of the temple is too small. Ideally, it should be at least 30 centimetres. However, only very few models have this value. With a smaller diameter, working with the trimmer requires full concentration, otherwise exactly what the handle is supposed to prevent happens: plants are trimmed that should have remained standing. Particularly high-quality devices allow the user to change the diameter of the handle.

The number of gears

Most cordless lawn trimmers have two gears: a slightly weaker one for the simple mowing tasks and a stronger one for the more demanding tasks. However, there are also models that have only one gear. Other devices even have three gears. In principle, one gear is sufficient for the occasional gardener who only needs to work on a small lawn. For somewhat larger areas with varying vegetation, two gears make more sense. Three gears are only worthwhile for professionals.

The volume

As already mentioned, the noise level is one of the big advantages of cordless lawn trimmers over alternative devices. Good models only reach a noise level between 72 and 75 decibels. This is quieter than most domestic hoovers. By comparison, petrol-powered lawn trimmers reach 90 decibels and more. So they are considerably louder.

Possible accessories

Safety goggles are indispensable, because it is impossible to avoid plant debris being whirled upwards during trimming. The goggles have the job of preventing it from flying into your eyes. Some gardeners also wear respiratory protection when trimming lawns to prevent the debris from entering the mouth and nose. Heavy work gloves protect the hands

Professional gardeners also wear a safety helmet when trimming when working near trees. The purpose of the headgear is to protect against falling branches. Amateur gardeners who trim in the shade of trees should not do without the helmet either.

A second batteryis also a useful accessory. The prerequisite is that you choose a cordless lawn trimmer where you can easily change the battery. The second battery ensures that the user can continue to work even if the battery used is empty or has a defect.

A quick charger is also useful in this context. The chargers that come with cordless lawn trimmers take an average of three hours to completely fill an empty battery. Fast chargers need less than half that time. Top models fully charge the battery in 45 minutes.

Castors – yes or no?

The most expensive cordless lawn trimmers have wheels. Users do not have to carry them around the garden because these models can be pushed or pulled. For most users, this is an unnecessary extra that has to be paid for: with a weight of two to three kilograms, cordless lawn trimmers are relatively light anyway. Moreover, they are usually only used for 15 to 30 minutes at a time. The wheels do make use easier, but not to an extent that justifies the extra cost for most users.

Battery lawn trimmer in use

Frequently asked questions about cordless lawn trimmers

There are several frequently asked questions about cordless lawn trimmers. We have answered the three most common ones for you.

What does a cordless lawn trimmer cost?

Roughly speaking, four price levels can be distinguished:

  • Devices for few users with low demands: 20 to 60 euros. These models are underpowered, often not well made and usually only have one gear. They are not recommended.
  • Discounter: 60 to 80 euros. The large discounters offer cordless lawn trimmers time and again. In terms of price, they usually range between 60 and 80 euros. The quality is sufficient for occasional users. However, these devices are hardly suitable for demanding work.
  • Entry-level: 80 to 100 euros. This is the price segment for cordless lawn trimmers, which are the best offer for most private users.
  • Professional: 100 euros and more. Those who work professionally and/or have corresponding demands on their own garden should plan 100 euros and more as an investment.

Where to buy a cordless lawn trimmer

Cordless lawn trimmers are available in DIY stores, specialised gardening stores, large electrical stores and supermarkets. However, the latter do not usually stock cordless lawn trimmers all year round, but only at certain times. In spring and autumn, these devices are often on sale.

Specialised online shops or the well-known sales platforms on the net such as Amazon are good alternatives. In most cases, buying online is more recommended, because interested parties have a larger selection. In addition, the prices are usually lower. In addition, you can find testimonials, product tests and guides. Interested parties thus gain a relatively reliable picture of the quality of the product before they buy it. Local retailers, on the other hand, have only one advantage: the buyer can take the cordless lawn trimmer with him immediately.

When should you use a cordless lawn trimmer?

As explained above, the devices are primarily intended for places that are difficult to reach. They are mainly used in marginal areas of meadows or beds. In some cases they are also used to remove wide-ranging overgrowth. Rather unsuitable and therefore untypical, however, is their use as an alternative to the lawn mower when larger meadows are to be trimmed. The cutting tool of a classic lawn mower is larger than that of a trimmer. It is therefore more suitable for large areas.

Fig. 1: © TwilightArtPictures / | Fig. 2: © andranik123 /