An explanation of cordless drill battery voltages and Ah ratings

If you are a bit baffled by the concept of 12 V, 18 V or 24 V cordless drills, the following article might be for you. Lets go back to basics here. If you really know all about voltage and current fuel feed through to skip this. I don’t want to bore you, but for some people this might be useful to understand what kind of cordless drill or saw they should choose.

When you see a cordless drill quarter saw advertised as 18 V or 24 V, the V stands for volt, or voltage. Voltage is like a measure of the speed at which electricity flows-you might recall seeing that mains voltage in many countries is 240 V, or 110 V. The higher the number of volts, the faster the electricity flows – generally speaking anything above about 50 V is considered dangerous to touch, as the electricity will be traveling “fast” enough to go right through your body and potentially injure you.

Cordless tools operate on what is considered to be a relatively low voltage, and as such you are unlikely to ever be in danger of electrocuting yourself with a cordless drill or saw.

It stands to reason that the faster the flow of electricity, the more power can be delivered to a motor. But this reason the new generation of 24 bold cordless drills are usually more powerful than the older generation of 18 V, let alone 12V drills or saws.

The other measure that you will come across, is A, or Ah. A is the abbreviation for amperes, and is a measure of the volume of power that is flowing. The high this number, the more power is flowing at any one time. The abbreviation Ah which you often see on cordless drill batteries stands for ampere hours. For example, 2.4Ah means that the battery can supply a flow of electricity at a rate of 2.4 amperes for a period of one hour.

Let’s put this together: you have an 18 V drill batteries, that is rated at 2.4 Ah. This means the electricity is flowing at a speed of 18 V, and can flowed at a maximum volume of 2.4 and peers for up to one hour.

This is all pretty technical, and you really don’t need to go into too much depth. All you need to remember is that higher voltage, and higher and peer rating means you’ll get more power and more lifespan at your battery. Most cordless drill batteries that you will find now rated at 18 V, often 24 V, and can range in output from 1Ah to 3Ah.

The traditional type of rechargeable batteries that were used in cordless drills and saws were of the NiCad (or nickel cadmium) chemistry. These batteries were okay, but they did not hold charge very well, and also did not have a very high energy density. Energy density refers to how much energy they battery can hold, are given weight. It becomes important to consider energy density with any hand held tool, because you don’t want it to be too heavy to hold, but you still want enough power to get the job done.

The next generation of battery cells were known as NiMH, or nickel metal hydride. These batteries had many advantages, being faster to recharge, and holding more energy per weight. Nickel metal hydride is still used in some cordless tools, and are a relatively inexpensive choice. They can be produced in any shape and size – for large appliances to tiny cordless screwdrivers.

By far the greatest technological advance that has been made in cordless drill battery packs however, has been the advent of lithium based cells. Lithium is a very reactive metal, and scientists have found numerous ways to combine it with other compounds to make batteries with incredibly high energy densities. This means you can now get cordless drill batteries which are lightweight, and will run your tool for a very long time.

Most manufacturers supply two battery packs with your cordless power tool. Because of the relatively fast charge time to these modern cordless drill battery packs, this is generally sufficient for home use. However, you may want to buy additional batteries for the occasions where you will be using more than one cordless drill or other  cordless tool at a time, or if you are going to be using your cordless drill battery somewhere where you will not have an opportunity to recharge it. Buying additional cordless drill battery packs is fairly expensive, but is a worthwhile investment if you rely heavily on your tools.

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