Is Higher Amps Better?
When you are looking for the most powerful tools, it may seem like higher amps are always better. But the truth is that, when talking about motor efficiency, higher amps isn’t always the solution. Let’s take a closer look at amps to understand when more is better.
What are Amps?
An ampere is a measure of electrical current. In a tool, it measures how much electricity the wires and motor can handle and bring to the work. However, it is not a measure of power or force. For that, you need volts.
What are Volts?
Volts are a measure of force. It’s how much force that electric current actually brings to the work at hand.
What are Watts?
Watts are amps x volts, and are a measure of the total power of a motor. Because the simple mathematics is that watts equals amps times volts (watts=amps x volts), you can often achieve the same amount of power with high amps and low voltage, or low amps and high voltage.
When are High Volts Better?
Higher voltage is better when current has to travel long distances. A low amp and high voltage system allows you to reduce the amount of electrical current, so less of it is lost as it travels through wires, while still delivering the same amount of horsepower at the end. Electrical transmission grid systems use high volts and low amps.
When are High Amps Better?
High amps are often used when power doesn’t have to travel long distances, when the system can be more efficient. Battery power often uses high amps, because the distance the current has to travel is so short that power isn’t lost during transmission.
How do Amps Affect Power Tools?
As you may already suspect, the importance of the amp rating on a tool depends on whether it is corded or battery powered.
Amps in Corded Power Tools
Corded tools are UL rated and have fairly standardized amps. However, the amps alone aren’t the total measure of power; look for the volt rating as well to compare total power of two different corded tools.
Amps in Battery-Powered Tools
In a battery-powered tool, amps measure not just how much power the tool brings to the work, but how long the tool can go between charges. In battery-powered tools, amps measure both power and time, which is why you often see battery powered tools rated for “amp hours,” or “Ah.”
What are Amp Hours in a Cordless Tool Battery?
In the simplest terms, amp hours is a measure of how long a battery can deliver 1 amp of current in a circuit. So a 2.0 Ah battery delivers current for twice as long as a 1.0 Ah battery, if all other factors are equivalent. However, if the attached motor is drawing 4 amps of current, a 2.0 Ah can power it for half an hour. If your batteries have an amp hour rating, and the motor has an amp rating, you should be able to simply divide one by the other and arrive at your battery life.
It Quickly Gets Complicated
What most people want from amp hour ratings is a simple way to know how long the batteries will last under load. However, in real-world conditions, it isn’t simply a matter of calculating amps, volts, and amp hours and arriving at battery life. There are a number of complicating factors.
Resistance and impedance
For accuracy, you would also want to measure resistance and impedance in the circuit, to see how much current is actually being delivered to the work, instead of being lost in the system.
Serial vs. parallel
How the battery cells are connected, whether they are in serial or parallel connections, affects how the battery behaves under load. Serial connections increase the voltage, but not the amp hours. Parallel connections increase the amp hours, but not the voltage. Parallel connections draw the same amount of power from every cell equally, making them work together and prolonging overall battery life. Serial connections draw power unequally, producing more heat, which leads to…
Battery cell size
Batteries stop working when they overheat, so cooling is a factor. Larger cells are cooler under load than smaller ones, but larger cells cool themselves less efficiently.
In other words, the only way to accurately calculate how long a tool will operate under load is to be a manufacturer with thousands of dollars of testing equipment, or to field-test tools and batteries yourself as a consumer.
Ultimately, in tool batteries, volts are the measure of force, and amp hours are the measure of time. Put another way, if a battery-operated power tool was a horse, volts represents the total size of the horse, amp hours represent how much food and water the horse is stocked with, and those two factors determine how much power your horse has. The total watts (volts times amps) measures either how long your horse can go in terms of time, or how much weight your horse can pull in terms of power. Higher amps is always better in terms of more potential energy, but that potential isn’t always actually brought to the job at hand. For that, you need volts.