I've been thinking about doing this too since I have 4 cordless
drills that wont hold a charge. My plan is to buy a cheap switching
PC supply and attach it to my workbench and use the 12v supply to
power the drill(s). These supplies can be picked up pretty cheap
(a 500 watt supply on pricewatch.com is $13 delivered) and can
handle 10+ amps on the 12 volt supply so I think it will handle
it Ok. It won't be portable but all I really want is to be able
to use these drills on my workbench (I have other corded and cordless
drills for mobil usage). If I end up doing this, I'll let you know
how it worked...
I have one of those Makita 18v cordless sliding miter saws, and I
thought about hooking a power supply to it somehow, but I'm not sure
how much current the motor would pull. I don't use the saw very often,
and I usually have to recharge the battery every time I break it out.
I too would like to know if anybody has successfully done this, and
what type of power supply they used.
Now for this application what you need is a charger permantely wired to
the battery. That way at a job site where there isn't power you can run
it without plugging it in. Then when there is power the battery will
charge some in between cuts. If after lots of cutting the batter is
getting week then just go do something else for a while.
Now as for how to acomplish this. Open up the tool and add a small
power plug like a headphone jack to the tool. Not the battery.
Batteries do go bad. By modifying the tool you get to replace the
battery when you need it. Then take an old battery of that will fit in
your charger. Take it apart, remove the batteries and attach a cord
with the correct plug on the end. This way you can use your existing
The only mod to the tool is a small (3/16) hole. Then install connector
and wire in parrallel with the battery connection. Use at least 18
guage wire to connect the connector to the battery contacts. Then use
at least a 18 guage power cord attaching the modified battery to the
plug. What you want is an 18 guage path from the charger through the
cable to the tool. Otherwise the quick charger might not work. Quich
chargers often generate over 1 amp of current and have to measure the
voltage at the battery to tell if it is charged. You need really good
connections so that the charger works properly.
Then lets say you are making a 10 second cut every couple of minutes.
The battery should never get low.
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