The Battery Life of a Cordless Drill

If you own a cordless drill (or any other cordless power tool for that matter) you know that the battery is the drill’s lifeblood. Without it, the drill is just a useless collection of plastic and metal. As such, battery life becomes a crucial consideration when you are contemplating buying a new cordless drill and once you have it, you also need to care for it properly in order to get the most out of it for the longest period of time. In this article we’re going to discuss the issue of battery life and battery care as it applies to the cordless drill.

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Lithium-ion vs Nickel Cadmium

While there are exceptions to every rule the fact is that most cordless drills being sold today use either a nickel cadmium battery or a lithium-ion battery. If you’ve owned cordless drills in the past you’re probably familiar with the nickel cadmium battery. However, the lithium-ion battery, while it’s been standard in mobile phones and laptops for some time, has only recently made the move to power tools. Each type of battery has its advantages as you can see here:

Nickel Cadmium Batteries

●            Widely compatible with most chargers.
●            A history of reliability.
●            Relative affordability.

Lithium-ion Batteries

●            Compact size.
●            Light weight.
●            Faster recharge.
●            Hold their charge longer

As you can see from this basic comparison the nickel cadmium battery, although relatively “old” technology by current standards nonetheless has earned its seat at the table by virtue of its proven reliability and the fact that it’s compatible with a vast number of chargers. While the lithium-ion battery is gaining ground in the marketplace due to its light weight, compact size and the fact that it holds a charge longer. That is, you can keep it in your tool box for months and when you finally pull it out to use it will still have a charge.

Performance Comparison

  • Nickel Cadmium – While nickel cadmium batteries are no doubt reliable, well understood and compatible with most of the chargers out there at the moment they also suffer a couple of significant drawbacks. Each has an impact when it comes to battery life and/or performance. The first is called the “memory effect”. In a nutshell when you discharge then recharge a nickel cadmium battery from the same point a number of times in succession they’ll “remember” the point at which you hooked them up to the charger and expect you to recharge them at that point every subsequent time. If the battery then passes that typical recharge point without being hooked up to the charger the voltage will suddenly drop. This can cause the battery to appear to die even though it still has a bit of a charge left.

The second issue is sometimes known as “lazy battery”. This is a type of voltage depression that results from continual overcharging of the battery. With a lazy battery the battery may appear to be fully charged when you put it into the drill but then discharge completely after only a few minutes of use. The lazy battery effect has left more than a few contractors scratching their heads wondering what just happened.

  • Lithium-ion – Lithium-ion batteries on the other hand have no such issues when it comes to the memory effect. You can recharge them however you want and it won’t affect the battery’s performance. They also suffer far less self-discharge than nickel cadmium batteries. Up to 50% less in fact. Which means, as we said, you can literally store a half-charged lithium-ion battery for months and it will retain a charge. The lithium-ion battery also operates effectively in a wider temperature range than the nickel cadmium battery. Here are a few more facts about lithium-ion battery performance:
  • Lithium-ion batteries exhibit close to 100% efficiency which allows for identical amp hours both in and out.
  • Lithium-ion batteries can be discharged 100% as opposed to around 80% for most nickel cadmium batteries.
  • The typical lithium-ion battery can be recharged up to 5000 times, maybe more. That’s 10 times the number of recharges you’ll get from a standard nickel cadmium battery.
  • While plug-in drills will always have a power advantage over even the best lithium-ion battery the lithium-ion battery will nonetheless maintain steady voltage through the discharge cycle. Nickel cadmium batteries by comparison will drop in voltage as the battery discharges.

However, while all these things are great and true, “lithium-ion” by itself does not equal greater power. Power is determined by voltage so an 18V lithium-ion battery has the same power as an 18V nickel cadmium battery. The mere fact that a battery is lithium-ion also does not mean that it will have greater run time than a nickel cadmium battery. Run time is determined by a combination of voltage, capacity and the tool’s efficiency not just by the nature of the battery.

Comparison of Environmental Impacts

  • Nickel Cadmium – Nickel cadmium batteries obviously use cadmium which is a heavy metal similar to lead and mercury. Like those 2 heavy metals it is considered extremely hazardous and therefore special considerations are in play when it comes to disposal. In fact the US government imposes a kind of disposal tax on nickel cadmium batteries that you pay when you buy the battery (whether you’re aware of it or not). The revenue from this pseudo tax helps cover the cost of proper disposal at the end of the battery’s life.
  • Lithium-ion – Lithium-ion batteries by comparison are environmentally friendly since lithium is a nonhazardous material. Still, these batteries come with hard plastic casings which should be properly recycled rather than simply tossed in the trash.

Cost Comparison

One advantage of a nickel cadmium battery is that it typically costs 40%-50% less than an equivalent lithium-ion battery. There are a number of reasons for this and lithium-ion batteries have been gradually coming down in price, but they still have a ways to go before they can compete with nickel cadmium batteries on a price basis.

Storing a Lithium-ion Battery

If you don’t plan to use your lithium-ion powered cordless drill for a while make sure the battery is charged to around 40% and then store it in a cool dry place. Because a lithium-ion battery charged to 40% and stored at 32 degrees Fahrenheit will only lose about 2% of its charge over the course of an entire year that makes the refrigerator the ideal place to keep your lithium-ion battery. Don’t worry, it won’t contaminate your food or beverages. And just in case there was any question, storing your lithium-ion battery in the fridge also means removing it from the drill first.

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Storing a Nickel Cadmium Battery

If you intend to store your nickel cadmium battery for a prolonged period of time they should be stored either fully charged or fully discharged (unlike lithium-ion batteries which should be 40% charged). Like lithium-ion batteries it’s suggested you store your nickel cadmium battery in a cool dry place that has a constant temperature. Once again the refrigerator would be ideal, although not the freezer. Storing your battery in the freezer may result in the formation of ice crystals in the battery which can impact performance and, in extreme cases, cause irreversible damage.

Additional Suggestions for the Care of Your Batteries

Today’s cordless drill batteries are hardier than their predecessors of 20 years ago but that doesn’t mean they’re indestructible. You should avoid dropping your batteries – whether lithium-ion or nickel cadmium – at all cost because they’re encased in plastic that can easily crack and compromise the integrity of the battery. Also, if your battery comes with plastic terminal covers don’t toss them out, use them to prevent the terminals from coming into contact with metal objects in your toolbox or bag (like screwdrivers) that could cause a short.

Selecting the Right Battery Voltage

The reason plug-in drills remain popular is that there’s no limit on the amount of power you can draw to run the drill. You can really lean into the toughest drilling job and not have to worry at all about the drill running down the way it will with a battery. This touches on an important issue: selecting the right battery voltage for the job(s) you have in mind.

Generally for light drilling work you’ll want a 12 volt battery. For moderately difficult work you’ll want either a 12 or 18 volt battery and for heavy duty you’ll want at least 18+ volts of power. Keep in mind though that if you have a really difficult job lined up you’re always better off using a plug-in drill than a cordless drill. That’s because, as we mentioned, although cordless drills are wonderfully convenient they’re still no match power-wise for the good old plug-in drill.

Warranty

Lastly, it’s important to remember that in most cases the battery for your cordless drill will not come with a warranty. Just why that is is open for debate. Many feel it has to do with the haphazard way some people treat their equipment but whatever the actual reason it just is what it is. The best way to ensure you’ll get the most out of your battery then is to simply take care of it properly. Don’t toss it around, don’t store it improperly. Follow the guidelines when it comes to charging and discharging. Avoid triggering the “memory effect” in your nickel cadmium battery and always store your batteries in a cool, dry place; preferably one with a constant temperature. Do all that any you’ll get years of use out of your cordless drill battery.

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