Cordless Power Tools

Cordless power tools have the ability to be incredibly useful. Having a drill and a saw with no cord that you can take were you please and use as you please… especially in our house of few electrical outlets, these tools are amazing.

I was hasitant to invest in battery operated tools at first, however, for experience had shown me that the batteries liked to fail. My father’s cordless tools didn’t last more than a year or two before the batteries were shot. And those batteries often cost upwards of $60 to replace. It’s just obscene! They seem to be built to fail, then cost far more than the sum of their obsolete, NiCad parts. What’s the deal?

First things first, most people have a little better luck than my father. Often the batteries can last for about 2 years of occasional use before they stop holding a charge. Interestingly enough, most people don’t leave the batteries in the charger 24×7. Therein lies my father’s mistake.

For some odd reason, these cordless power tools usually come with the simplest charger possible: A wall transformer that connects directly to the battery terminals, constantly charging while the battery is connected. Sometimes there is a little indicator light to let you know it is charging.

Let it be known that these chargers will destroy batteries.

The true killer of these batteries is overcharging. To understand this, lets take a look inside the battery.
While a battery discharges, a chemical reaction occurs involving metals, oxides and ions. The reaction is always happening slowly within the cell, but it goes much faster when current is allowed to flow across the cell. Once the metals are depleted (or are getting close to being depleted), the battey stops working and the reaction is reversed. By applying a voltage to the cell, the metals begin returning to their original status. This can only continue so long as there are chemicals in their discharged state. Once the cell is fully charged, if the electricity continues to be applied, something bad starts happening. The metals are in water containing electrolyte. If you have ever seen what happens when you run electricity through water, you know where this is headed. Electrolysis begins happening to the water – breaking it down into Hydrogen and oxygen and creating large amounts of heat. Now the battery has gas bubbles – steam, hydrogen and oxygen. All modern batteries are designed to deal with this and have gas vents; however this process is what destroys the battery. A battery that is never charged to the point of elecrolysis will last a much longer time.

Since we have no way of knowing the state of the battery’s charge, we cannot know precicely when to get that battery off the charger when using the supplied charger. So what is a reasonable person to do? Some high-end manufacturers (bosch, delta) sell quick chargers that ensure battery safety. But if you’re like me, you have a craftsman, or coleman, or Black & Decker tool and there is no intelligent charger. And for that matter, the quick chargers run near $100.

There is hope. for less than $20, you can purchase the components necessary to turn your current charger into an intelligent charger that charges fast, stops when the battery is fully charged, then “trickle” charges the battery to safely maintain a full charge. (Trickle charging essentially applies current to the battery at the same rate it loses power when sitting. Thus there is no electrolysis, no overcharging.)

Would you like to know how? Stay tuned.

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