Updated March 2022

When DeWalt introduced their 20/60V FlexVolt batteries, it caused quite a sensation. This battery technology is unique to DeWalt and quite remarkable. The concept of a dual-voltage battery seemed impossible to some. To the engineers at De Walt, it was a challenge worth undertaking.

While many cordless tool enthusiasts have become familiar to the concept, there are still many folks who still ask the question: what is the difference between DeWalt 20V MAX and FlexVolt? This article covers the topic in detail. Even if you understand the basics, you will have a much better understanding of the DeWalt 20V MAX vs FlexVolt debate after this read. 

What are the advantages of using a 60V battery vs 20V? How does the DeWalt FlexVolt battery work? Are FlexVolt batteries worth it? Can you use DeWalt FlexVolt batteries for 20V MAX tools? These are all valid questions that need to be answered. I’ll be providing these answers and much more. 

I understand battery technology better than most, thanks to my electrical engineering background. From this point of view, I’ve been appalled at some of the misinformation that has been presented by many so-called experts on other sites. Many have stated that using a 60V platform provides more power than 20V. This is wholly untrue, but there are advantages to using a higher voltage. All of this will be explained logically in the DeWalt 20V vs 60V article. 

Get the facts and dispell the myths. 

DeWalt FlexVolt battery price
DeWalt 20V MAX battery price

How important is battery voltage?

Cordless tools have come some way since the 1970s. One thing is the change in battery voltage. Just about all tool brands have increased battery voltage to improve battery efficiency. Most of the earlier cordless used 12V batteries. I guess the idea of a 12V battery was set in people’s minds as this had become the standard for auto and leisure batteries. At some point, someone decided there was no need to stick to this standard when smaller power tool batteries can offer more advantages when the voltage is increased.

One of the reasons why I really like DeWalt is that they have not discontinued the older batteries and tools as new, higher-voltage models came along.   We’ve seen a move from DeWalt 18V to 20V, and then 60V (which also includes a few 120V tools). This has not always been so much about producing a more powerful tool. It’s more about power efficiency. The greatest advantage of this is longer working times from the battery.

Power vs Voltage vs Current

You probably remember seeing the formula P = VI back in school. I’m sure you’ve forgotten all about it by now. Thankfully, I haven’t. It’s been a part of my daily life for several decades. So understanding voltage vs current vs power is like second nature to me.

Essentially, this is what the P = VI equation is all about. This describes the relationship between potential difference (V), current (A or I), and power (P), usually expressed in watts. To completely understand DeWalt 20V/60V batteries, we need to fully under the relationship between power, volts, and current. 

Power (P): As a power tool user, power is certainly the operative word. A perfect place to start with this explanation. Every tool, whether powered by gas, an electric cord, or a battery has a power rating. This will be expressed in Horsepower (HP) or watts (W). More powerful tools may use Kilowatts (KW), which is simply watts X 1,000. The unit of measurement isn’t of particular importance, it’s easy enough to convert one to the other – 1HP = 745.7 W (or 0.75 KW).

Now for the really important bit: you can produce any amount of power (W) regardless of the voltage (V). In other words, a 20V battery can provide the same power as a 60V battery. The current (A) will increase as the voltage is reduced. This will become an important part of the discussion as we proceed.

Voltage (V): Potential difference is measured in volts and is probably the least understood electrical principle. Even though it is pretty basic. The word potential is an important one here because it has a lot to do with the potential for energy, rather than the actual energy.

The concept of voltage vs current is easily explained if we use water as an example to visualize it. When you open a faucet, two things affect how much water is available: pressure and flow. High water pressure will force more water through the pipe. Flow is about gallons per minute and will be affected by the diameter of the pipe.

Now pay attention to this. You can get more water from a narrow pipe by increasing the pressure. We can translate the same principle of water pressure to electrical voltage. Increasing the voltage will allow for a higher current using a thinner conductor.

Impedance (I): Electrical impedance or current is measured in amperes (A). To avoid any confusion, take note that the letters “A” and “I” refer to the same thing: current.

Impedance, or current flow, is related to the resistance of a conductor vs the potential difference. The two are interchangeable. Back to the water analogy. Continuing with the volts equals water pressure example, Amps will be the resistance of the pipe carrying the water. A narrow (small diameter) pipe will offer more resistance to water flow than a wide pipe.

You can increase your water flow rate by either increasing the pressure or the pipe gauge. If you’re looking at how fast you can fill a bucket from a faucet, either will have the same net result. It will take roughly the same amount of time to fill a 2-gallon jar at 10PSI from a 1” pipe, as it would with 20 PSI from a ½” pipe.

Now it’s time to apply this principle to the electrical formula P = VI. I’m going to use the example of a 500W cordless tool, powered either by a 20V or 60V battery. This means that P remains the same for both (500W), V changes (20V or 60V), therefore I will change relative to V, to ensure the equation balances.

P = 500W

V = 20V or 60V

I = ? (unknown amps)

20V MAX: 500W = 20V X  25A.

60V MAX: 500W = 60V X 8.3A.

This simple example makes one thing clear; power is combination of volts vs amps. Increasing the voltage (V) proportionally reduces the current (A). By increasing the voltage three times, from 20V to 60V, we have reduced the amps three times, from 25A to 8.3A.

How important is amperage?

To start off on the amps discussion, I want you to picture two extension cords, a 30’ 15A cord and a 30’ 30A cord. The first thing we notice is that the 30A extension cord is twice as thick as the 15A cord. Double the amperage and the cable thickness also doubles.  

If increasing the voltage reduces amperage, it follows that the conductor can be thinner at a higher voltage. 

Now we have the first reason why increased voltage is an advantage. The size and weight of the conductive materials are decreased, reducing both the weight and bulk of the tool. Since the 60V battery has three times lower amperage than the 20V battery, the conductors for a 60V MAX tool can be three times lighter.

Okay, when we look at the price difference between 20V MAX tools and batteries, compared to 60V MAX, it hardly makes much sense to pay so much more just because the tool has a slightly better power-to-weight ratio. Since conductors only constitute a small proportion of the weight, it is hardly noticeable.

So why have the engineers spent so much effort changing battery voltage?

There is a much more important effect of increased amperage that we haven’t looked at yet. The hidden villain in all electrical equipment –  heat. The reason conductor size is increased relative to the amperage is because of the heat generated. With increased amps, more heat is generated. If the conductor is too thin, it will melt.

Heat affects battery efficiency and the performance of an electric motor. As the heat increases, battery time (and lifespan) decreases. The electric motor, supplied by the battery, becomes less efficient at high temperatures. Therefore, as the increased amps cause the temperature to rise, this reduces the power output produced by the motor.

Increased temperature means increased Amps. Not a good thing. Every battery has an Ampere Hour (AH) rating. This tells us how many amps the battery can supply for an hour before recharging. If the tool requires a 30A current to supply the power needed, we can calculate the expected working time as follows.

Using a 6AH battery at 30A: 6/30 = 0.2 hours working time.

A battery will provide power for a longer time if the amps are reduced. If the amperage is reduced to 10A,  tool, this would be the result:

Using a 6AH battery at 10A: 6/10 = 0.6 hours working time.

Here’s what we can conclude from all this. A cordless tool can produce all the power needed, regardless of the battery voltage. The benefit of increasing the voltage is to reduce the amperage. The tool has a better power-to-weight ratio and functions more efficiently because of lower heat transfer. A more efficient tool will use less battery power, extending working time.

The FlexVolt Advantage

We’ve established that there are obvious advantages to using a 60V MAX battery vs 20V MAX. Yet, there is one more unique characteristic that gives the DeWalt 20V/60V MAX battery the edge over all other batteries. FlexVolt technology is just one of those ultra-cool innovations that shows true DeWalt ingenuity.

All the top power tool manufactures have been increasing the battery voltage for their cordless tools. For those of us who have been using these tools for many years, we have quite a collection. Every cordless tool owner knows the advantage of sticking to one battery platform. Using the same type of battery for a large selection of tools is just so practical. You don’t need to own a bunch of different batteries. You can simply take the battery from one tool and use it in another. You only need one type of charger, which is cheaper and reduces unwanted clutter.

When the manufacturer upgrades to a new battery platform, changing the voltage, you cannot use the new battery in your older tools. Old batteries become redundant, and you lose all the benefits of using one brand (one battery) for all your power tools.

DeWalt sought to address this conundrum by developing the 60V/20V MAX FlexVolt battery. This is a dual voltage battery, the only one of its kind in the world. From an electrical engineering standpoint, this is a perfect example of a simple solution to a complex problem.

How does the DeWalt FlexVolt battery work?

I’m filled with admiration for the guys at DeWalt for this innovation. The FlexVolt battery is pure genius. It works on the same principle as any other battery. I should start by explaining this.

All batteries are made up of numerous battery cells, generally ranging from about 2V to 5V. To obtain the correct battery voltage, these cells are connected in series. A 12V battery is generally made by using 6 X 2V cells connected in series, or 3 X 4V cells.

If you wish to increase the AH, you can connect cells (or groups of cells) in parallel. If the 12V battery, used in this example, was made up of 3AH cells (at 2V), the battery will have a power storage capacity of 3AH, when using 6 cells connected in series. The series connection of six cells increases the voltage to 12V but the ampere hours remains unchanged. If we take an additional six cells, connect them in series to obtain 12V, then connect these two groups of 12V cells in parallel, we end up 6AH. Essentially, what we’re doing is creating two 12V batteries from 2V cells, then connecting these two batteries in parallel to double our power storage.

DeWalt took the principles of series and parallel cell configurations and combined them in one battery. The idea is simple, connect more cells in series to increase the voltage. Alternatively, split the cells into groups connected in series, then connect these groups in parallel. The end result is a battery with a lower voltage and increased AH.

The Science of FlexVolt.

DeWalt FlexVolt explained

FlexVolt 20V/60V cell configuration

Inside every DeWalt 20V/60V FlexVolt battery are 15 X 4V cells. The image above clearly shows how these batteries can be connected in series or a combination of series and parallel. It is all controlled by a simple mechanical switch. Old-fashioned trusted technology used to achieve high-tech results.

If you look at the top of the FlexVolt battery, you’ll see a small yellow triangular switch. When the battery is inserted into a 20V tool, this triangular switch is depressed by the wall of the battery compartment. With this switch pressed in, the battery cells are switched to the 20V configuration. This means 3 groups of 5 cells create 3 X 20V battery groups. These three groups are connected in parallel to increase the AH.

The 60V (and 120V) DeWalt cordless tool have an indent in the wall of the battery housing. This keeps the switch in the open position. Consequently, all 15 cells are connected in series to generate 60V.

I’ve noticed a lot of confusion around the AH rating for FlexVolt batteries. This is essentially a misunderstanding around the P = VI explanation given earlier. Remember, as voltage increases, Amperage decreases accordingly. If we’re looking at the other side of things, the battery, we need to remember that the same basic principle applies. As battery voltage increases, the AH decreases.

A FlexVolt battery that uses 15 X 3AH cells will have a different rated storage capacity, depending how the cells are configured. With 3 groups of 4V cells, we have a 20V battery with three times higher AH. So the cell rating of 3 AH becomes 9 AH, when connected in both series and parallel. When we connect all the cells in series, the AH remains unchanged, at 3AH. Hence the same battery can be either 20V 9AH or 60V 3AH.

As is the way of marketeers, the best looking specs are always presented. Because the AH rating is higher at 20V, DeWalt FlexVolt batteries are rated by the AH at 20V, which is three times higher than the rating at 60V. When you see a 9AH FlexVolt battery, it means 9AH at 20V, or 3AH at 60V. Even though the AH rating is lower for the 60V configuration, the working time is actually improved. You need less amps to supply the same power at a higher voltage. As we’ve established, less amps means less heat, and this is the most efficient way of doing things.

DeWalt 20V MAX battery price

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