"Tips", from my shop work #2: upgraded charger wow,

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Blog entry by hobby1 posted 12-21-2013 02:10 AM 1452 reads 0 times favorited 4 comments Add to Favorites Watch
« Part 1: TIP, using a LiL, Basic electronics to repair power tools Part 2 of "Tips", from my shop work series Part 3: solving for slat width and length in a diagonal pattern in a frame. »

It looks like these cheap battery drills and batteries, aren’t so cheap afterall, they don’t hold a charge very long, thats what I used to think, but now I’m thinking its not so much the batteries but the minimal charger capacity they give you in these kits, if I can charge this drill so fast and strong charge, because the xformer, can carry a larger load, then with careful charging time, I can get maximum charging on these cheap battery tools, and get exceptional use out of them, insted of frustrations with there charge performance.

I’m glad I learned this from this broken charger, it opens up a whole new way of getting the maximum usage from cheap battery tools.

4 comments so far

View mantwi's profile


312 posts in 1921 days

#1 posted 12-21-2013 03:24 AM

Well? How did you do it man? This is something a lot of us would love to learn how to do. Share.

View hobby1's profile


335 posts in 2323 days

#2 posted 12-21-2013 04:18 AM


This will only work for the very basic transformer and diode rectifier charger, some chargers use elaborate circuitry, for trickle charge and sensors, these should not be tampered with unless your a electronics technician. Which I am not, I am, just a hobbiest.

My charger happened to be a simple transformer, with a 4 diode fullwave bridge rectifier, this kind of charger can’t get any simpler than that, so when I discovered that the original transformer had an open primary winding,


I disconnected the secondary winding from the circuit board, and in its place I soldered in a larger “radio shack” power transformer, I had laying around, the original xformer, was rated at 250mA. this new one I put in, is rated for 1.2A. so it can handle a larger load

I just soldered the secondary windings of the new xformer, in the same place of the original, then using wire nuts connected the primary windings to a lamp cord, taped everything up nice and tight so everything is electrically safe, and plugged it in and checked for output voltage at the polarized plug that goes into the tool, and got a reading of around 15v dc, with no load, so I knew I had enough voltage and current (power), to take the load of charging the battery.

That’s why when I plugged my drill into this charger, I waited a few minutes, and already the drill was charging to the point, where I could hold the chuck and the drill would ratchet on the middle setting of torque, so after around 5 minutes the speed was fast and I had maximum torque.

I think it’s because with a larger capacity xformer, it can deliver more current to the battery, quicker, because it has more capacity to do so,.

However, under these conditions, I need to be careful to not leave it on the charger to long,
or unattended,,
because I don’t know if it could cause the battery to overcharge, and damage it, but if I can charge it quickly within minutes to get back to using it at maximum torque during a project, it’s worth giving it that quick charge from time to time.

As a safety notice to anyone trying this,

This has not been tested long enough to determine if battery damage could occur with this much current capacity, so do this at your own discretion.
Only do this if your familiar with working with house current.

View Medic409's profile


6 posts in 1778 days

#3 posted 12-21-2013 06:00 PM

Great hack and solution. Do you or can you provide some pics or at least what type of charger it is(harbor freight, etc.)? A simple work around for your charging time would be to plug it into a simple AC timer so as not to burn your house down.

View hobby1's profile


335 posts in 2323 days

#4 posted 12-21-2013 07:42 PM

This is the charger that came with the B&D drill, this is a pic. off the innernet,

mine is all taped up into a big wad with this new transformer, I put in.

But the internals, for this type is made up of a miniature power transformer, with the mains prongs hardwired to the primary coil, and the secondary windings connected to a tiny circuit board, with individual discreet diodes soldered in, to work as a “fullwave bridge rectifier”, then on the output side of the rectifier, is the wire with the jack plug that goes into the drill.

I only charge my tools during the time I’m out in my shop.
I unplug everything when I leave my shop.

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