American Woodworker

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Protect Batteries from Overcharging


I own several inexpensive cordless tools—for the money, they can't be beat. The no-frills battery chargers they come with, though, don't automatically shut off after the battery is recharged. Yet according to the operator's manuals, I may shorten the life of the batteries if I don't remove them promptly. Unfortunately, I only get into my shop on weekends. If I forget, a battery could be left overcharging for a long time. I found a $14 solution to my problem at my local hardware store: a “security” timer, normally used to turn lights on and off on a daily cycle. These timers have a grounded plug and outlet and dedicated on and off clips. The timer plugs into a recep-tacle on the charging station I built. The chargers plug into a power strip and the power strip plugs into the timer. Now, I never have to worry about overcharging. I simply install the dead battery, plug in the charger, place the timer's off clip to allow the recommended charging time and turn on the timer. After the timer shuts down, the off clip can't turn it back on.

Intermatic, Heavy-duty grounded timer, #TN311C, $14.

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kcgary wrote re: Protect Batteries from Overcharging
on 04-10-2009 6:10 PM

To start the timer, the "on clip" has to be inserted...

Then, do you remove the "on clip" after you turn the timer on?

Seems like you would need to do this each time, or it would turn on again in 24 hours.

Please let me know.



bricofleur wrote re: Protect Batteries from Overcharging
on 05-24-2009 8:51 PM

I use the same kind of timer when using my household iron to glue Melamine edge strips to Melamine particleboards. I forgot it once and it could have produced a desaster.