A good cordless tool battery will help a tool perform its best, and this buying guide gives shoppers the info they need to get the most out of their cordless tools.

Because the battery is what makes it possible for cordless tools to do their work, choosing the type of battery technology that the tool uses is almost as important as the choice of tool itself.
For example, if the battery’s capacity, charge time, or storage characteristics are mismatched to the work or user, the expensive tool it’s attached to might not do the user much good.

Cordless power tools are used all over, and they’re becoming even more plentiful. Manufacturers release more cordless models, and more powerful models, every year. On top of that, power tool battery technology is also seeing rapid changes. This means that there are more battery options out there(and we’ll probably be seeing more), and that many of those batteries are expected to do heavier work than ever before.
The best thing that shoppers can do is be as informed as possible about battery designs, performance, specifications, and features to keep up with the industry. The information in this article gives cordless tool users and shoppers the head-start they need to choose the right rechargeable battery types for their cordless tools, and then get the most out of them.

The Different Battery Types for Cordless Drills

Finding a cordless drill which will fit your needs best can be complicated. There are a large number of different features and specs to consider, not the least of which is the type of battery used. There are three different types of batteries which can be used by cordless drills, or any other kind of cordless tool: nickel-cadmium (NiCd), nickel-metal hydride (NiMH), and lithium-ion (Li-ion). Let’s take a good look at each of them.

Nickel-Cadmium Batteries

NiCD batteries are the oldest of the three types and they are still widely used because they are irreplaceable when it comes to performing in tough conditions. In addition, they are inexpensive and their cycle life is quite impressive. Overall, Li-Ion and NiMH are better, but if you come across a cordless tool that uses NiCd batteries, don’t be too quick to dismiss it.

One of the reasons NiCd batteries haven’t been retired yet is their general toughness and resistance to impact, as well as both high and low temperatures. Also, their cycle life measures at around 1,000 charges, which is really impressive. In addition to that, they deliver a better flow of electric current. Although keeping the battery in a state of deep discharge is far from recommended, if you do so with NiCd batteries, they will not damage as easily as their Li-Ion or NiMH cousins. If you look at the whole thing from an economic standpoint, NiCd batteries are also significantly less expensive than the other options.

Seeing as NiCd are the oldest type of batteries, some of their characteristics are a bit dated. For example, they weigh more than other options, and their capacity is lower. One thing you need to be careful of if you use NiCd batteries is to not let their charge drop below 70% between charges. To do so diminishes their lifespan. However, you should perform a deep discharge once every month or so, or NiCd batteries will suffer from memory effect. Another thing to keep in mind is that NiCd batteries need to cool down before being recharged. And there’s one more thing: if you care about the environment, you may be disappointed to find out that cadmium can damage the environment when not stored properly.

NiCd batteries in a nutshell:

About 1,000 charge cycles, meaning long cycle life

Acceptable 15%-20% discharge

Low capapcity of 1.2Ah – 2.2Ah

Fast charge times

They require proper maintenance, such as a deep discharge every month

High memory effect impact without regular maintenance

Extremely durable and tough

Nickel-Metal Hydride Batteries

NiMH batteries are more expesive than NiCd batteries, but they also feature some improvements over their NiCd counterparts. One of the biggest improvements is that NiMH damages the environment far less. Their biggest advantage is their capacity, which is sometimes 2 or even 3 times greater than that of NiCd batteries, thanks to better energy density. Like NiCd batteries, though, NiMH batteries are sensitive to improper storage and charging conditions. They weigh less than NiCd batteries, and they are less expensive than Li-Ion batteries.

However, NiMH batteries are very sensitive to storing and charging conditions and they need to be stored and maintained properly to extend their cycle life. Unlike NiCd batteries, NiMH batteries are more sensitive to both high and low temperatures. A good rule of thumb is to store and use them between 33°F and 103°F. When left unused or in a state of deep discharge, NiMH will experience far more damage than NiCd batteries. Their lifespan and storage capacity will shorten. Just like NiCd batteries, they should also be charged at 70% capacity, but with one deep discharge performed every three months to circumvent memory effect.

NiMH batteries in a nutshell:

Cycle life depends on storage and maintenance, but can reach that of NiCd batteries

Fast self-discharge of 20%-30%

2.2Ah to 3.0Ah capacity

Fast charge times

Moderate maintenance which typically includes a deep discharge once every 3 months

Less memory effect than that of NiCd batteries when properly maintained

Very sensitive to heat

Lithium-Ion Batteries

Being the newest of the three types of cordless tool batteries, Li-Ion batteries are also your best option, when all aspects are taken into account. Of course, they are not without their drawbacks. For instance, they are more expensive than both NiCd and NiMH batteries. Their biggest enemy is heat, which deteriorates their internal components and changes the electro-chemical processes going on inside. Age and continuous use also play a big role in the shortening of their life span.

Although it may seem they are not the best option due to their short life cycle, they have higher capacity and they are able to charge quickly. The technology of Li-Ion batteries is still being improved, so it will be interesting to see what happens with them in the future. One of the things that doesn’t need improvement is their weight, because they are the lightest of the three types of batteries. Also, I mentioned earlier that NiMH have high energy density, which is also the case with Li-Ion batteries, but Li-Ion batteries are less sensitive to variations in temperature than their NiMH cousins. While other types of batteries require regular maintenance because they are susceptible to memory effect, Li-Ion batteries do not suffer from such ailments.

While the other two types of batteries have to stick to a specific shape, so tools kind of have to be designed around them, the construction of Li-Ion batteries allows them to take on any form, so they can be physically designed to provide a tool with better balance and/or performance. And when it comes to storage and recharging, as long as you don’t store them in an environment which is too hot, you can pretty much use them any way you like because they don’t suffer from self-discharge or memory effect. Their charge/recharge cycle is also superior to the cycles of the other types of batteries. Best of all, unlike NiCd batteries, Li-Ion batteries do not damage the environment.

Li-Ion batteries in a nutshell:

Shorter life cycle: only 300-500 charges, or 2-3 years

The most expensive of the three types of batteries

Almost no self-discharge

Very high capacity: 3.0Ah and up

Require little to no maintenance

No memory effect

The Summary

As you can see, Li-Ion is definitely the way to go, but their prices are significantly higher than those for NiCd and NiMH batteries. Even so, NiCd and NiMH batteries are still better in some aspects than Li-Ion batteries, and depending on the kind of work you do, they might just be a better choice. I hope this little guide will help you decide which battery standard you should choose.

 Rechargeable Battery Characteristics

There are a few terms and characteristics about rechargeable batteries that shoppers should become familiar with before setting out to make a cordless power tool purchase.
Things that affect a battery’s overall life and run time are usually the determining factors when power tool battery shoppers zero in on a decision (after cost of course), so most of the characteristics explained below have some influence on how long a battery will last.

cycle life-

The overall life of the battery, usually expressed as the number of charge cycles that it can withstand before completely losing its charge capacity or ability to transfer energy. For example, NiCd batteries tend to have a cycle life of 1,000 charges (cycles) or more.

All rechargeable batteries eventually wear out, although they wear out for different reasons.

Age, use, and memory effect can all contribute to the inevitable death of a power tool battery, depending on the battery type.

Users often have to choose between a long cycle life and other attractive features, like run time. For example, because they can run longer between charges than other battery types, the shorter cycle life of Li-Ion batteries isn’t usually a problem for users who care more about keeping their tool in operation for longer periods.

self-discharge-

All rechargeable batteries slowly lose their charge when not in use, but some batteries lose their charge much faster than others.

For some users, batteries with fast self-discharge rates aren’t a problem, especially if their cordless tool’s see little or no storage. Batteries with a slower self-discharge rate become more important for tool users who plan to user their cordless tools only occasionally.

voltage-

Voltage determines how much power a battery can deliver at a given time. Simply, cordless tools with higher voltage are more powerful.

Rechargeable power tool batteries are usually a cluster of individual cells. The combined voltage of the cells determines the battery’s overall voltage; however, different types of batteries (NiCD, NiMH, Li-Ion) have different individual battery cell voltage capacities.

For example, the battery for an 18v cordless drill with a lithium battery would consist of around 4 individual Li-Ion battery cells, because Li-Ion batteries can typically deliver 3.6v-4.2v per cell. Individual cell voltage for NiCd and NiMH batteries are about 1.2v and 1.4-1.6v, respectively.

Very roughly, and with some overlap, the scale for matching tool voltage to workload is like this:

Light Work:         7v-15v
Medium Work:   12v-18v
Heavy Work:     18v-36v

capacity (run time)-

This is the amount of time a battery can operate its tool between charges. A battery’s capacity it usually expressed as the amount of amperage hours (Ah) that it can deliver.

“Ah” is different than the tool’s overall amperage rating (the current at which the tool operates). Instead, Ah represents how much energy flow the battery can hold, not the level of current during operation.

When shopping for cordless tools and their batteries, just remember that a higher Ah means longer battery use between charges.

deep discharge-

Deep discharge means allowing a tool battery to completely drain of energy through normal operation. Deep discharge can be a problem for some batteries, and drastically reduce a battery’s cycle life and capacity. For other battery types, deep discharge is not a problem.

Also , some batteries require deep discharge periodically to keep the battery healthy. This additional maintenance can be a hassle for users who do not use their cordless tools often.

memory effect-

Memory effect happens when a battery is charged over and over again without being allowed to fully drain. The idea is that somehow the battery “remembers” how much it is being recharged, and then adopts the shorter charge range as its new charge capacity.

Interestingly (and confusingly), the nickel based batteries that are susceptible to memory effect retain their capacities best when they are charged after dropping to only 70% of their capacity. However (and this is the trick), they must be allowed to deep discharge periodically so that the battery “remembers” its true capacity.

Some rechargeable batteries are sensitive to “memory effect,” and some are not.

NiCad vs Lithium Ion: Which battery is better for cordless tools?

Steady advances in voltage and applications have made cordless tools the first choice on most projects for you and professionals. For years NiCad (Nickel Cadmium) batteries reigned supreme. Recently, though, they’ve been displaced by newer Lithium Ion battery technology.

Lithium-ion batteries are smaller in size, require less maintenance and are environmentally safer than Nickel-cadmium (NiCad) batteries. While they have similarities, Li-ion and NiCd batteries differ in their chemical composition, environmental impact, applications and costs.

Which battery is right for your cordless tool?

That depends on the job and your wallet. Typically, Lithium-ion batteries are smaller and lighter than a NiCad battery. Lithium-ion also two to three times more expensive than NiCad. On the other hand, Lithium-ion has virtually no self-discharge. This allows a lithium ion battery to be stored for months without losing charge.

One does not provide more power than the other. An 18V Lithium-ion battery has the same potential to deliver power as an 18V NiCad battery.18V is 18V. How long it provides it is another story. The best measure of run time is how many holes are drilled or how many boards cut on a single battery charge. In this test, Lithium-ion battery-powered tools win.

That has more to do with the efficiency of the tool than the battery itself. Brushless motors in most Lithium-ion-powered tools make better use of battery power. That leads to the misconception that the battery has more power.

NiCad batteries range in capacity from 1.3Ah to 3.0Ah. In comparison, Lithium-ion batteries range from 1.1Ah to 3.0Ah. Just as the gas tank size is only one factor in how far a vehicle can drive on a tank of gas, applications per battery charge factor in voltage, capacity and the efficiency of the tool. Clear as mud?

NiCad batteries

Nickel-cadmium batteries suffer from a “memory effect.” The battery remembers the point in their charge cycle where recharging began. During subsequent uses, voltage will drop at that point as if it had been discharged. That’s why it’s wise that you use a NiCad battery until it’s totally dead before recharging With this kind of proper use, a nickel-cadmium battery can last for 1,000+ cycles before losing capacity.

Lithium-ion batteries

Lithium-ion batteries, on the other hand, are low maintenance. They resist the “memory effect” and tolerate a wider ranged of temperatures. Their only serious drawback is fragility. They also require protection circuit to keep working safely.

Both will perform for roughly the same number of cycles. While the Lithium-ion battery may provide more voltage, it does so at significantly higher cost compared to a NiCad battery.

Since absolute performance is roughly equal, choosing between Lithium-ion and NiCad batteries come down to simple differences: Lighter, longer-lasting and more expensive, or heavier, more consumable and cheaper. The choice is yours.