Cordless Tools Battery Guide: Which Type is Best?

In Cordless Tools by Aaron Green4 Comments

cordless tool battery guide

cordless tool battery guideWhen it is time to purchase a new cordless tool, you have a lot of specifications to look consider. Whether it is a cordless mower, battery drill or something else you are after, the one part of the tool that is always there, is the battery. It also may just be the most confusing specification to consider; there are so many numbers, types and ratings that are thrown at you when you are shopping you end up just relying on the advice of the sales staff at the store.

Well let’s give you a bit of an education and go over the different battery types, ratings and everything else you need to know regarding batteries for cordless tools.

Article Contents

How Battery Technology Has Improved

Battery technology has improved vastly over the past decade, and in some cases the tools that they power can perform just as well as a corded tool.

One of the main problems with batteries in the past was their ability to last the distance. There is nothing more annoying than having your battery run out of juice half way through a job. Modern day Li-Ion batteries can provide power for extended periods of time, and also recharge quite quickly –  making them a worthwhile invesment.

If you told a carpenter that you relied on nothing but a battery drill to do all your screwing and drilling jobs 15 years ago they would have laughed at you, these days cordless drills, nailguns and other such cordless tools are their most used devices.

Which Battery Type is the Best for Cordless Tools?

The cordless tool industry has grown exponentially since the release of the Li-ion battery because of the vast improvement over the other older battery types.

So yes, I know that some of the other battery types listed in this article are outdated, but they do still have their uses and they are still sold with some cordless tools.

So if you want the quick answer as to which battery type is best, then you will probably want to go with a Li-ion battery.

Of course there are many other things to consider, so if you want to learn a bit more then please keep reading.

Understanding Battery Capacity & Specifications

When you are shopping for a cordless tool, you will notice that you are bombarded with different battery specifications.

The most common specifications that are all over the packaging and marketing materials are voltage (V) and amp-hours (Ah). Well surely it is easy right? Just choose the biggest numbers and you have the best battery? While this seems like the obvious answer, it does depend on numerous factors which we will look at.

Let’s quickly explain some of the most commonly used terms when it comes to cordless tool batteries.

cordless tool battery specificationsAmpere-Hour (Ah)

Ah, or ampere-hour is the total amount of charge your battery can deliver in one hour. E.g. Under ideal conditions, a cordless lawn mower that continuously draws 2.0 amperes (amps) of current will drain the total charge of a 2.0Ah battery in 1 hour.

So by that logic, a 4.0Ah battery should last for 2 hours in the same electric mower. This is all assuming of course that the mower draws a constant 2.0A and that conditions are ideal for the battery – which never happens in the real world.

There is another thing to consider here, and that is the fact that a 4.0Ah battery is not necessarily going to last twice as long as a 2.0Ah battery will, in some circumstances it may actually last more than twice as long. It all depends on the type of battery, how it is wired up and the control circuitry in the battery itself.

But you can still use the basic reasoning mentioned here to roughly judge how long a battery might last.

So to put it simple Ah is a measure of how much charge the battery can provide. A simple analogy would be the size of the fuel tank in a car.

Battery Voltage

The voltage (V) rating of a battery is a measurement of how much power that battery can provide. In very simple terms, the higher the voltage the more powerful the battery. Some cordless devices require more power to run, so a cordless drill that is designed to drill through tough timber is going to need more power than a drill that is only designed to do light work.

Yes, higher voltage generally means the tool is more powerful – but it also means more weight in the tool and usually it will cost you more as well. It all comes down to choosing the right tool for the job, remember that bigger is not always better.

Memory Effect

They memory effect occurs when a battery is constantly partly drained, then charged without being allowed to fully discharge. The name comes from the fact that the battery remembers how much of its charge was drained before being charged and then uses the shorter charge period as its new capacity.

Not all batteries suffer from the memory effect.

Battery Cycle Life

charging li-ion batteryCycle life is a measurement of how many times a battery can be charged before losing the ability to retain energy. For example, Li-Ion batteries in cordless tools generally have a cycle life of 300-500. So theoretically you could charge a Li-Ion battery at least 300 times before it would need to be replaced.


After a cordless tool battery has been charged, if the battery is not used straight away then it starts to slowly lose its charge. Some battery technologies have a much faster self-discharge rate than others. Keep in mind that a faster self-discharge rate is not always bad – if your tools are never stored away for long periods between use then you probably won’t care about the self-discharge rate at all. Self-discharge is measured in percentage of charge lost per month.


A deep discharge is allowing the battery to completely drain of energy through use. This can be problematic for some battery types (not all) and can severely reduce the batteries cycle life and capacity.

On the flip side, there are some battery types that should periodically be allowed to deep discharge in order to maintain a healthy battery.

Cordless Tools Battery Types

Most guides that you read about cordless tools batteries will be focused mainly on Lithium Ion (Li-Ion), Nickle Metal Hydride (NiMH) and Nickel Cadmium (NiCd) batteries. As a bonus however, we will also look at Lead-Acid batteries because they are still quite common in some cordless lawn mowers.

Nickle Cadmium (NiCd) Batteries

The Nickel Cadmium battery has a long history, in fact it was first invented in 1899! Of course it only started being mass produced in 1946 and it grew in popularity from there. They are generally out performed by both NiMH and Li-Ion batteries but are still useful for some jobs today.

cordless nailgun battery NiCd Batteries at a Glance

  • Cycle life: 1,000 + charges
  • Self-discharge: 10%
  • Ah rating: 1.2Ah – 2.2Ah (low)
  • Requires deep discharge regularly
  • Susceptible to memory effect

NiCd Battery Pros

  • Very cost effective
  • Robust and not easily damaged
  • Long life cycle – around 1,000 charges
  • High current flow

NiCd Battery Cons

  • Heavy compared to Li-Ion and NiMH
  • Low capacity  (Ah)
  • Must be cool before being recharged
  • Regular deep discharge required
  • Not environmentally friendly (contains cadmium)

Nickle Metal Hydride (NiMH) Batteries

Brought into mass production in 1989, NiMH batteries are a much newer technology. They are an improvement on NiMH batteries in many ways, the main points being that they are less toxic to our environment when disposed of, and have significantly improved capacity (Ah). They do of course come with some downfalls which can be seen in the following sections.

cordless drill battery

NiMH Batteries at a Glance

  • Cycle life: loses capacity after around 600 cycles, although this can be improved upon if charged and stored correctly
  • Self-discharge: 13.9–70.6% at room temperature
  • Ah rating: 2.2Ah – 3.0Ah (medium)
  • Requires a deep discharge semi-regularly (every 2-3 months)
  • Is susceptible to memory effect but can be reduced with proper charging. Memory effect is also reversible to a degree by carrying out a few proper charge/discharge cycles

NiMH Batteries Pros

  • Capacity is higher than NiCd batteries
  • Costs less than Li-ion batteries
  • Cycle life can be greatly increased by storing and charging the batteries correctly
  • Safe for the environment

NiMH Batteries Cons

  • Sensitive to temperature and should only be stored and used when between 33 degrees F – 103 degrees F
  • Allowing NiMH batteries to continuously deep discharge will reduce the lifespan and reduce storage capacity
  • Lack of use over long periods of time can be detrimental to the batteries lifespan and capacity
  • When in use you should not let a NiMH battery fall below 70% capacity except when doing your maintenance deep discharge
  • Cost more than Ni-Cd batteries

Reconditioning NiMH Batteries

If your NiMH batteries have developed a memory effect or capacity has been reduced, then it is likely you can recondition them by following this guide at

Lithium-Ion Batteries (Li-Ion)

Entering commercial production in 1991, the newest technology in batteries for cordless tools is the Lithium-Ion battery (Li-Ion). As far as we are concerned, Li-Ion batteries are the best choice for cordless tools, whether it is a cordless lawn mower or a cordless drill.

Li-Ion batteries do not suffer from a memory effect and they are not affected by poor charging habits. Li-Ion batteries instead wear out over time due to age and use. The main downfall of this type of battery is the relatively short life cycle (<500 charge’s)

cordless mower battery

Li-Ion Batteries at a Glance

  • Cycle life: <1900 cycles (depending on design and make of battery)
  • Self discharge: 8% at 21 °C (much higher though as temperature increases)
  • Ah rating: 3.0 Ah and up!
  • Requires no maintenance
  • Is sensitive to heat and impact

Li-Ion Batteries Pros

  • Very light-weight
  • Self-discharge rate is very low at normal room temperatures
  • No memory effect
  • Very high capacity

Li-Ion Batteries Cons

  • High temperatures during use or charging can cause the batteries to explode, although most feature adequate safety features to prevent this
  • High cost compared to other battery types

Lead Acid Batteries

Lead acid batteries are not commonly thought of when it comes to cordless tools, but they are still quite common in cordless lawn mowers so we have decided to give them a small section in this article.

The lead acid battery was first put to commercial use in train carriages in 1859, it has obviously had multiple revisions and improvements since then but is still widely used today for a number of applications.

Lead Acid Batteries at a Glance

  • Cycle life: <1200 cycles
  • Self discharge: 3-20%
  • Ah rating: Varies with battery size

Lead Acid Batteries Pros

  • No memory effect
  • Very safe and rarely explode or catch fire
  • Low cost

Lead Acid Batteries Cons

  • Loses significantly more capacity in cold weather than Li-ion
  • Worse for the environment than Li-ion due to much more mined material being required
  • Lose voltage slowly as they discharge resulting in less power
  • Lose the ability to be recharged if left discharged for too long
  • Very heavy

Charging Cordless Tool Batteries

In the past, you could mix and match different chargers with different rechargeable batteries. These days most cordless tool batteries are designed to work with a specific charger, especially those with Li-Ion batteries. You will find that Lead Acid batteries can be charged in many different ways, but it is always best to follow the manufacturers instructions and use the charger that the manufacturer provided with the tool.


Replacing Cordless Tool Batteries

When it comes time to replace your cordless tool batteries, it is generally easy to find suitable replacements online these days. Amazon has a wide variety of batteries as will your local tool supplier. If you are having trouble finding a replacement battery then try contacting the manufacturer.

Pricing last updated on 2018-06-21 at 14:44 / affiliate links - Details

4 Comments on “Cordless Tools Battery Guide: Which Type is Best?”

  1. I have had several Nicad drills. They last only so long even if not charged and used regularly. Over a period of a few years the batts. will not hold a charge.

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