How to Choose a Cordless Power-Tool Battery

Building your tool kit takes a lot of thought. You’ll need to consider the impact differences from one tool to another, and the possibilities of going for what a specific brand has to offer. Tradies require tools that are dependable, will last in different conditions and settings, have the grunt when faced with demanding tasks, and still show up the next day for a repeat.

Tools are an investment, but for many, it’s what brings home the bacon. DIY-ers can pass for much less, but still need something that inspires confidence and the urge to improve skills. Choosing what’s right then will determine whether you get the job done, and whether that job is to the required standard and within the set timeframe.

One key area that has seen a tectonic shift is how tools are powered. Gone are the days of huge tools straggling even heavier cords and extension reels. Tools have become lighter, and thanks to the practicality of reliable and durable cordless batteries they’re now portable too. This brings in a whole heap of advantages.

Any tool with a cordless battery will be easier to get to the worksite, and often the only tool that you can use in places lacking nearby power, such as new construction sites. It also means working outdoors and in dubious weather is much safer and void of any needless stress. There are no cords to get in the way, or be the reason for workplace injuries as has often been the case. And no worries that plugs, sockets, or cords are damaged.

Choosing the Right Battery

Battery Types

Lithium-Ion (Li-ion) tool batteries might not be the last word in the newest battery technologies currently available, but they are by far the most widespread in cordless tools. This is what is also moving the growing EV industry forward. The technology is replacing yesteryear’s Nickel Metal Hydride (NiMH) and the batteries that were seen in the first iterations of cordless tools, and ones that began the gradual move to cordless.

Almost all major tool manufacturers now deploy Li-ion in their tool lineups. The reason is that they can be optioned smaller and lighter, retain charge over longer periods, and have no draining self-discharge when not in use. In addition, lithium batteries can be built to apply enough voltage to a range of different tools, while still retaining longer run times by bumping up battery capacity. I’ll explain these points in further detail below.

Tool Compatibility

Of course, you’ll want a battery that will power a tool the way it’s meant to. The most obvious is having a battery of the same brand as the tool. Yes, there are general-purpose (and often cheaper) cordless tool batteries that can fit across the whole board of tool brands, but the performance and run time you get will be dubious at most. Manufacturers spend quite a bit of time and effort in optimising how batteries work with particular tools.

Some will have more grunt in tools faced with periodically difficult tasks, while others will provide a constant charge for longer in simpler and smaller tools. One key advancement that increases efficiency is the use of brushless motors, and proprietary tech in circuitry designs and safety features. Here all manufacturers have fancy names that claim to improve overall performance.


Voltage is stated in V, and roughly equates to the power the battery supplies. Generally, the more voltage the more power, and often the heavier and bigger the battery. Going for the biggest figures here is not always needed. You won’t need the biggest battery in tools that are fine with 12 or 18V variants, since this adds unnecessary weight and will affect balance and handling. But for bigger tools like mitre and circular saws faced with tough materials, then you’ll need all the power you can get. Here tool makers have 36 and 54V units for any tasks needing more power. Some also supply power tool batteries in 72 and even 94 volts.

Ampere-Hours (Ah)

Words like ‘fuel’ and ‘extended range’ aren’t used in a lot of battery names by chance. This refers to the available time a battery will power the tool or the rated Ampere-hours. Think of this as the amount of fuel a vehicle has in the fuel tank. Smaller batteries start out at 2Ah, so in ideal conditions will provide 1 amp of current for 2 hours or 2 amps for one hour.

You’ll find these batteries in most smaller cordless tools. A 5Ah (and what’s becoming the bare minimum for professional use) will consist of more battery cells (with each cell providing 3.6V) connected in parallel, or in simple speak packs two smaller 2.5Ah batteries in the same housing.

Overall run times are impacted by several factors, the most crucial being how hot the battery gets when discharging and powering the tool, and the outside ambient temperature. For this reason, almost all makers of Li-ion cordless batteries use their own take on cooling technology. The aim is to get the most out of the battery before it needs to be recharged.

Other Factors to Consider

Lithium-ion batteries have largely resolved issues that plagued many batteries in the past. Things like ‘memory-effect’ in Ni-MH batteries, or difficulty in charging batteries that haven’t been fully drained, are non-existent in a Li-ion battery. Also, this battery type isn’t prone to losing charge (‘self-discharge’) when sitting on your workbench or stored in a toolbox.

What is of note though, is that lithium batteries have some of the longest life cycles, meaning how many times they can be discharged and charged again. Most newer variants have 500 or more life cycles. For a pro using the battery every day, this means the battery will last at least two years. For powering tools used infrequently, a decent battery will get you over 10 years of fun, assuming you keep it charged and well-maintained.

Lastly, most things boil down to price. Batteries with smaller voltages and shorter run times will be cheaper. But, they may not provide enough power for the tool or tools you often use. Larger batteries can get expensive, with those in really high voltages often costing more than the tools they power. Generally, the higher the voltage and amperage rating the more expensive the battery.

Choosing a Cordless Tool Battery Charger

Once the battery has drained, it’s time for a recharge. As with batteries, here look for chargers of the same brand to get batteries topped up faster and safer. Different types of chargers will be handy for different uses. Single chargers for instance can handle one battery at a time, but may also have features that will charge it faster.

Dual chargers can charge two batteries of the same or different type, so charging an 18V 2Ah and a 54V 9Ah battery is also a possibility. If you’re buying your first cordless tool, prices are lower by going with packaged sets that include a suitable battery for the tool and a decent charger.