Cordless tools FAQ

Over recent years the number of cordless (i.e. battery powered) tools available has grown enormously. In many cases mains power is but an extension lead away, and so you may not “need” a cordless tool. There are some items (notably drills and powered screwdrivers) for which the cordless tool is desirable and in class of its own - often in addition to a mains equivalent.

If in doubt as to whether to go cordless (for things other than drills) you are probably better sticking to mains.

The golden rules of cordless tools

• They cost more
• They will deliver less power than a similar price / size mains tool
• If you don't use them often, then they may well be flat when you want to use them! (less of a problem with modern Li-Ion battery tools)
• The batteries have a limited life

There is also a huge difference between the best and the worst examples. The worst cordless tools are virtually useless. The best can be used as non- stop work horses.

The cordless jigsaw I was once given is a nice example. Cost was about £14 from a large DIY shop. In theory it will run on a full charge for 10 minutes, the reality is 30 seconds of full power, followed by ever decreasing speed and power for the next 5 minutes, with the remaining battery capacity being in effect unusable. Recharging then takes 14 hours. The one job I tried with it (a 9" cut in 1/2" ply) was completed.... just. Then that was it for the day!

Batteries and chargers

The biggest influence on the quality and usability of a cordless tool are its batteries and the charger. It is simply not possible to purchase good quality rechargeable batteries at very low cost. Many budget cordless tools are sold at a price that is less than the price of a decent branded battery, so something has to give! The quality of the batteries will can affect how long it runs, and the power or torque available. The quality of the charger will affect how long the batteries take to charge, and more importantly, how many times you can recharge them and still get useful performance from the tool.

Historically most cordless batteries used Nickel Cadmium (Ni-Cd) or Nickel Metal Hydride (Ni-Mh) chemistry. Modern tools will almost always be Lithium Ion (Li-Ion).

Modern Li-Ion batteries tend to get better performance from cordless tools that the older types did, so there is less disparity in performance between cheap and expensive tools. However cheaper tools may often lack some of the important circuitry to maintain safe operation of the battery in use and when charging (Li-Ion batteries need much more careful monitoring to prevent catastrophic failure). So they may be less tolerant of abuse (excessive discharge, hot charging etc)

Batteries will need replacement eventually. With a budget tool this will usually be a non economic exercise or they may simply not be available, whilst with a higher end tool it may well be more expensive than you anticipate.

Battery capacity, or where bigger really is better

A number you will see banded around with respect to batteries is the Amp Hour (Ah) rating. This number tells you something about how much charge a battery can hold. The more charge it holds, the more work you can get out of it between recharges (but the longer it will take to charge). With older tools using Ni-Cd, and Ni-Mh cells, battery quality tended to rise with capacity, so batteries with bigger capacities also tended to be better in other respects. The effect is less marked with Li-Ion batteries.

The Ah value on its own will only give a useful comparison between batteries of the same voltage. To compare capacities of batteries of differing voltages, you will need to use the Watt hour (Wh) figure that is sometimes also quoted (its the multiple of the Ah value and the battery voltage, so a 2.6Ah 18V battery will store just under 47 Wh of energy)

Higher capacity batteries need to be matched with better and faster chargers, otherwise you will be waiting longer for them to charge.

A good quality battery pack should take recharging many hundreds of times before it no longer holding enough charge. Some of the poorer ones may only last for a hundred or fewer charges. With batteries it is very much a case that you get what you pay for.

The only real advantage of lower capacity batteries is their lower purchase cost, and that they can make a tool lighter.

Are more “Volts” better?

In the quest for more power, performance and speed from battery operated tools, there has been a slide upwards in battery voltage. This suits the marketers well since there is a nice “number” to use as a sales hook.

The bigger the number the better right? Err, in some cases yes, but not always. The more volts, the more cells, the bigger and heavier the tool will be. If you want a nimble easy to use drill/driver this is not a “good thing”. Then we come down to quality of batteries again: a top end 14.4V drill will out perform an 18V or 24V budget tool for just this reason, while being smaller and lighter into the bargain.

However for very high performance cordless tools, higher voltages are a way of getting more power and more overall energy storage from batteries. So 24V, 36V and higher packs are becoming more common. Many tool makers will also produce some tools that will take two standard (typically 18V) battery packs at the same time. This allows users to add 36V high performance tools to their collection, without needing to invest in new chargers and batteries when they already have a collection of 18V packs available.

What about “Watts”?

Watts (W or kW) is the power consumption rating we are used to seeing on mains powered tools, but this quantity is not so often mentioned on cordless tools. Cordless tools are designed to balance the conflicting requirements reducing electrical power consumption to extend battery life while still maintaining enough performance to get the job done. This tends to make for a lower "Watts" figure to boast about on the box, and that is not as much use as a marketing hook. Many professional cordless tools may consume over 400W, but most are less powerful and consume far less. The dual battery and higher voltage battery tools can generate in excess of 1kW of output - in some cases more than the equivalent mains powered tool.

With all mains equipment, including power tools, the Watt figure stated is the input power, but the mechanical output power is rarely given. By the time you have accounted for all the heat and noise generated, the useful output power may be much less. Thus a well designed tool with good speed control and a well made gearbox may produce the same usable power at the sharp end as a less well made tool with twice the input power.

You can make a stab at estimating the actual power of your cordless tool by studying its performance. Say it runs for 15 minutes at full power, and has a battery capacity of 2Ah (Amp-hours). This tells you that the battery can delivery 2 amps for one hour, 4 amps for 30 minutes, or 8 amps for 15 minutes. We can therefore deduce from the time the battery lasts, and the capacity of the battery, that this tool is drawing about 8 amps from it. Multiplying the voltage of the battery by the current drawn gives the power consumption (Watts = Volts x Amps). So if this tool has an 18V battery we would get 18V x 8A = 144W.

Brushless tools

A modern development has been the introduction of "Brushless" motor tools. A brushless motor is a significant design change from a brushed motor, that does away with the need for a commutator and brushes to connect power to different motor armature windings in sequence. In fact it does away with the traditional wound armature altogether, and instead has a fixed magnet armature surrounded by field coils. The brushless motor uses an embedded micro-controller to sense the position of the rotor and energises the field coils in the correct sequence and timing to spin the armature.

Advantages of Brushless

• Motors are more power efficient - less energy is lost as heat. So longer battery life, and more torque / power.
• Better endurance - when used "hard" for extended periods, brushed tools can overheat their brushes and brush holders, resulting in a failure of the tool or complete "burn out" of the motor. Brushless motors are less prone to this type of failure.
• Motors are physically more compact, which allows tools to be smaller and better balanced.

Disadvantages of Brushless

• Tools are more expensive
• Tools are more complex and depend on more sophisticated controllers. This can make them harder to repair and service, since many makers only sell the field coil assembly, controller, and switch as a complete "assembly". This often means that even when the part is available, it can be prohibitively expensive.
• Brushless motors are slightly more noisy, and have a somewhat "harsher" sound.
• Motor speed control is slightly more "lumpy", moving up and down speeds in discrete steps, rather than a smooth ramp.

Which should I buy?

Consider brushless for tools that are going to be worked hard or for extended periods without a rest, or for applications that tend to drain batteries quickly. Examples of tools where this is true:

• Angle grinders
• Belt Sander
• SDS Drill
• Circular Saw
• Chain Saw
• Dust Extractor / Vacuum

Also consider brushless when you need a tool to be very compact - like a drill driver than needs to fit inside small spaces.

Other factors

For brushed motor tools in particular, another influence on performance, is the quality of the motor and speed controller. A good speed controller will deliver lots of torque and control, even at low speeds. The poorer ones will only deliver torque at high speeds which is far less useful. In recent years, many tool makers have upped their game with speed controllers.

Battery Platforms

All the bigger name tool makers have created standardised battery platforms, and a range of tools that can share those batteries. For tool makes this is one of the key ways that can "lock in" customers and keep them coming back for more tools, so as to better make use of your investment in the batteries and chargers. For consumers, this can be a good way to acquire new tools with a significant cost saving (so long as you stick to the same brand).

Body Only Tools

One of the key routes to benefitting from a shared battery is the availability of buying tools "body only" - i.e. without included battery or charger. The logic being, these are expensive, and you only need a certain number, since no matter how many tools you have, you will only likely be using a small number at a time. Body only tools are often significantly cheaper than buying the same tool with batteries and charger. This is a cost effective way to acquire new tools, although a buyer looking for a "first" cordless tool needs to look carefully at the deal they are buying... it might be really cheap because "batteries not included".

Many makers will adopt a standard naming convention for tools sold body only. Makita for example will add the suffix of "z" to the end of the model number to indicate this is the "bare" body only tool. Usually supplied in a cardboard box, with no batteries or charger.

Battery interchangeability

Generally batteries for tools from one brand, don't fit another. However there are sometimes ways around this. One can buy battery adaptors that will adapt the interface of a battery to a different makers tools. This can be an attractive idea - especially if you are mostly invested in one brand, but can't find a particular tool you need from the brand. There are however some limitations to the approach, since the adaptor may make the tool larger and less ergonomic to use. Modern tool batteries often also include more than just power connections between the tool and the battery. They may also include data that allows to tool to gain information about the battery temperature or its state of charge. These "extras", may not adapt so well between platforms.

Also it is worth keeping in mind that not all batteries are designed with the same goals. They may not all be able to deliver the same peak current, and this could affect the performance of a tool if paired with an "unexpected" battery.

Universal battery platforms

There have been some industry efforts between tool makers to adopt common battery platforms. These include:

Power for all Alliance

One example being the "Power for all alliance" which uses a standard battery made by Bosch. This has been adopted by a number of the smaller tool manufacturers.

Cordless Alliance System

Another platform is the Cordless Alliance System This is a collaboration with some 40 brands of tool that share a common battery. The brands include some "big names" like Mafell, Lanello, and Metabo (note not Metabo HPT (the US brand used to market Hikoki tools (formerly Hitachi Koki)))

PDNation

There are also some general purpose platforms like the PDnation Universal Power Tool Battery System by Ceenr, where the battery and the "interface" that allows it to mate with the tool are available as separate parts. The same battery pack can be connected to any brand of tool, by choosing the appropriate interface adaptor.

The "lock in" effect of brand specific batteries has also attracted the attention of some legislative bodies such as the EU with the Batteries Regulation (EU) 2023/1542 directive that addresses a number of quality and sustainability issues with batteries, as well as interoperability.