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Cordless Drill Batteries and Power Tool Battery Chargers FAQs

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Before you buy a new cordless power tool, it is useful to learn more about how their batteries and chargers work. This will help to ensure you are using the battery and charger correctly so that you can get the best performance from your tools.

Here are some frequently asked questions about how to use batteries and chargers from DEWALT and Black and Decker cordless power tools.

(Note: "Runtime" refers to the number of holes drilled, screws run, area sanded or cuts which can be made on a charged battery.

How is the Voltage of a Battery Pack Determined?

A Hitachi tool battery pack is made up of a series of individual battery cells connected together, each cell has 1.2 volts. With the addition of each cell the battery pack voltage increases by 1.2 volts. For example, a 12 volt battery has 10 cells of 1.2 volts.

Can I use a 9.6V battery in a 12V Drill?

No, you cannot use a 9.6V battery in a 12V drill. The tools are designed to run at the specific voltage provided by the battery pack. Too much voltage, as well as too little voltage, can cause poor performance and life from the tool. The tool may run for short periods of time with the wrong battery pack, but it shortens the overall life of the product. This is the same reason corded products designed for 240V cannot be used in the U.S. where they have 120V outlets or vice versa.

What is Battery Memory?

Memory is one of many conditions which cause a loss of runtime. Memory is created from repetitive light use in the exact same application (i.e. cordless phones, electric shavers, etc.) Power tool products rarely see light use or the exact same loads, due to variability from the user, the bit size, as well as the material. The same variability which causes different runtimes prevents cells from developing memory. Power tools are considered high-drain applications. Memory typically develops in lower-drain rate applications, such as cordless phones, etc, because the rate in which the battery is draining is continuously the same. Power tools draw higher currents and have sporadic drain rates minimizing the opportunity for the cordless drill battery to develop a memory.

Does the Battery Need to be Completely Discharged Before Recharging?

No. Just the opposite, you should stop using a battery as soon as you feel a substantial decrease in power from the tool. Completely running down a battery may damage the power tool battery. Do not tape the trigger to run down the battery.

Can you Leave Cordless Power Tool Batteries in the Charger?

This entirely depends on the charger supplied with your power tool and you must read your owners manual to answer this question. In some cases serious damage can be caused by leaving your Panasonic drill battery on charge, whereas in other cases it is recommended that you do leave your unit on charge. For example DEWALT chargers have a maintenance mode which allows batteries to remain in the charger, maintaining a fully charged pack until the user is ready to work. If the batteries are stored outside of the charger, they will discharge naturally, 15-20% the first 24 hours, 7-10% the next day, and about 1 % every day there after.

Why does my Battery not hold a Charge Anymore?

A battery may not hold charge for any of the following reasons:

What can I do to Improve the Runtime of my Battery?

If no permanent damage has been done to your cordless tool battery, you may be able to improve its runtime. A good slow charge is required, if your charger has the faculty for a quick boost charge this should be switched off. In all cases read your owners manual for specific instructions, however, generally the following applies:

  1. Discharge the battery under normal use. Remove the battery, once you feel a loss of power from the tool. Do not tape trigger on, this will make it worse.
  2. Let the battery sit out of the charger for at least 2 hours until the battery is at room temperature.
  3. Place battery in the charger overnight to allow for a full charge on each individual cell. (A minimum of 8 hours at room temperature.)
  4. If there is no difference in runtime, there is either permanent damage or the battery has reached the end of its usable life. In either case, the battery should be replaced.

Why is the Battery Warm when Removed from the Charger?

As a drill battery approaches a full charge, some of the energy being loaded into the battery generates heat. It is OK for the battery to get warm, but it should not get so hot that it is difficult to hold in your hand.

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