We all know the DeWalt 20V MAX range of cordless tools. They have become a staple for contractors, professional shops, and DIY enthusiasts over many years. When a cordless tool is this good, and affordable, why change? Then, along came the DeWalt 60V MAX FlexVolt battery and a new range of 60V and 120V cordless tools. The 60V FlexVolt battery has been around for a few years, yet many cordless tool buyers are still asking which is better, DeWalt 20V or 60V? This article should settle the DeWalt 20V vs 60V MAX debate for good.
I’ve written countless articles on the topic, but it seems to be an enduring question – DeWalt 20V vs 60V. I’ve also read many other so-called experts. I’m amazed at some of the garbage that some tool review writers come up with. I intend setting the record straight. Just the facts and how to understand them. For those who are new to this site, I wish to explain where I’m coming from. I know power tools. More importantly, I was in the electrical engineering business for many years. I understand batteries, volts, amps, and watts. It is with this insight, that I’m going to be comparing the DeWalt 20V and 60V battery systems.
I’m going to set the record straight from the very start. I’ve read and heard too many people claiming more volts means more power. If you see a battery comparison with these words, you can be certain the guy writing it has no idea of what he is talking about.
Though the DeWalt 60V battery is more than just a higher voltage battery. FlexVolt technology is an incredible feat of engineering. No other cordless tool manufacturer has accomplished this. Things might get a bit technical, when discussing DeWalt 20V vs 60V batteries. But I’ll try keep it simple. Let’s go through things in a step by step way, to get the full picture.
How important is battery voltage?
Cordless tools have come some way since the 1990s. One thing is the change in battery voltage. Just about all tool brands have increased the voltage of their batteries. Most started out around 12V and increased from there. One of the reasons why I really like DeWalt, is that they continue manufacturing the older batteries and tools when the new models come along. We’ve seen a move from DeWalt 18V to 20V, and then 60V (which also include a few 120V tools). This has not always been so much about producing a more powerful tool. It’s more about power efficiency, getting the best working time from your battery.
A battery that lasts longer is obviously more convenient. Battery lifespan and working time has been the greatest challenge for cordless tool manufacturers. DeWalt has been one of the leaders in this regard. Increasing battery voltage is one of the best ways of improving power efficiency, even it doesn’t mean any more power from the tool itself. I’ll explain this with some simple 7th grade science.
You probably remember seeing the formula P = VI some time during your school days. 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 the understanding of voltage vs current vs power is like second nature to me.
Essentially, this is what the P = VI equation is all about. It is the relationship between potential difference (V), the current (A or I), and the power P, usually expressed in watts. To completely understand DeWalt 20V vs 60V batteries, we have to form a clear idea of what these three components of the equation really mean and how they affect one another.
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 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) from any amount of volts (V). In other words, a 20V battery can provide the same amount of power as a 60V battery. It’s the relationship between voltage and amperage that changes. 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 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. In other words, by increasing the voltage, you can move more current through a thinner conductor.
Impedance (I): Electrical impedance or current is measured in amperes (A). To avoid any confusion take not that the letters “A” and “I” refer to the same thing: current.
Impedance, or current flow, has a lot to do with the resistance of a conductor vs the potential difference of the electric current. 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 waterflow than a wide pipe. Basically, 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 fill a 2-gallon jar at 10PSI from a 1” pipe, as it would with 20 PSI from a ½” pipe.
I hope the comparison between water flow and electric current has given you a picture to work with. Now its time to apply this to the electrical formula P = VI. I’m going to use the example of a 500W cordless toll, 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 has to change 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?
When calculating electricity supply and power, amperage is everything. To start off on the amps discussion, I want you to picture two extension cords, a 30’ 15A cord and 30’ 30A cord. The first thing we notice is that the 30A extension cord is twice as thick as the 15A cord. Twice the amperage, twice the size conductor. We’re starting to see a pattern here. We decrease the voltage and the amperage increases accordingly. The size of the conductor also increases proportionally.
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 less the amperage, compared to 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 in 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 electric equipment, heat. The reason why conductor size is increased in accordance to the amperage is because of the heat generated. At high 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 it needs to be recharged. If the tool requires 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.
To get the best working time from a battery, we want to reduce the amps required to power the motor. If this tool could run at 10A, it would look like this:
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. At a lower 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.
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.