Wall adapter for cordless tool

[Anonymous No.222163]

Hello DIY, is it possible to create a wall adapter for a DeWalt 9.6V 3/8 Cordless Drill DC750KA? If so, could you explain me how? please. I own this drill model and its working woderful but I've read the batteries die very quick. So I want to have an option just in case.

[Anonymous No.222170]

Yes, it is possible. I've seen it done but I'm kind of in the same bind you are. Either I've seen people do it but their methods have been sloppy, down right dangerous or they were using adapters that were close enough to their original drills current that very little work was needed. One guy on youtube did it by using aluminum foil as contacts for his adapter, ugh. In my case I have several Makita 7.2 and 9.6 volt tools and I've been unable to find a DC wall wart that outputs in those voltages. My other problem is matching the amp draw of the drill to the DC adapter. I have no clue what these drills draw and the batteries max out my multimeter at 10 amps! I'm guessing a 2 amp DC adapter might cover it but the only one I have is 12v and that means I would have to make a circuit to downstep the voltage and I have very little experience with that kind of electronics work. Anyway, bumping causes I'd like help in this area also. Pic related, its mah drill.

[truckerfag !!xXmBuWkIT3n No.222182]

>>222170
I FUCKING LOVE THAT DRILL

The 3" power saw in that series is nice also.

I'm assuming the most professional approach would be to begin by acquiring and gutting an extra battery pack, leaving the contacts and case as much intact as possible. If it was particularly flimsy without all the batteries in it, some epoxy filler might be in order once some beefy wires (somewhere around 6 gauge, or larger) have been properly soldered to the interior of the terminals.

As far as the specifics, I'm at a loss beyond the theory of converting AC to DC by use of a bridge rectifier.

Best bet is probably to crack open the drill, and go off the ratings on the side of the DC motor insofar as determining the needed input ratings.

[Anonymous No.222189]

You just need a dead battery to use for its contacts.
First use a multimeter to check the polarity of the contacts on a good battery and note it for later.
Remove the dead battery and BMS circuit from the casing, cut the leads, then resolder the leads onto the wires for an AC adapter (observing the polarity you marked down earlier) that's rated for a very similar peak voltage and a moderate amount of current. An adapter capable of 4 amps should be plenty for most smaller drills.

AC adapters are obviously cheapest if purchased from China through eBay.

Next time buy a corded power drill first, then go cordless for smaller projects. Having only a cordless drill is a headache when you're doing larger projects.

[Anonymous No.222201]

>>222189

Makita guy here. I have a DeWalt corded drill but its a pain in the ass hauling a huge cord around for some projects. Plus is a pretty beefy drill, it weighs more then my cordless ones. I was replacing the panels on my fence the other day and it freaking killed my wrists.

I've got a bunch of dead and dieing batteries for my Makitas (I bought most of the tools used off CL) but they can;t be opened without fucking them up. Guess I'll have to take a dremel to them or something.

[Anonymous No.222204]

What abuot this? http://dewaltownersgroup.com/index.php?topic=327.0

and how do I translate it to a 9.6V version?

[Anonymous No.222213]

>>can;t be opened without fucking them up
You're only going to need the contacts and latch. You can cut the bottom of it completely off.

[Anonymous No.222228]

>>222213

If I cut the bottom off I will be unable to remove the battery from the tool. This would be bad if I ever wanted to use it as a cordless again or if something broke I have been able to dig up some older batteries that seem to have snaps holding them in place but try as I might I can't seem to dislodge them to get the bottoms off..

[Anonymous No.222250]

>>222228

Fuck it. I cut the bottom of one of my 7.2 volt batteries to see what is what. This ones a little blurry but its good enough. Each side has 3 tabs, one large and 2 small. More pics to follow.

[Anonymous No.222252]

Derp.

[Anonymous No.222254]

Let me just make clear what a PAIN IN THE ASS this was. The 2 large tabs are 1/4 inch thick! They bend VERY little when with my full body weight on them even though they are hollow. In the end I had to drill out the 3 tabs on one side to pop the base out.

As you can see the terminals are not attached to the shell, that will make reusing them so much easier I think.

[Anonymous No.222266]

The wire running down the battery is probably a temp sensor of some type to keep the Ni-Cd from overheating. The chip next to it is labeled:
KLIXON (R) 7-S
4MM45B2-08 F 7 J 5

There are 6 batteries in total with the two central terminals connected to the top of each tube. At the bottom the two tubs are connected by a thin bridge of metal from one terminal to the other, as you would expect. The two smaller side terminals appear to go to the temp sensor. In addition one of the wires off of that chip has a small tab soldered to it that is in turn connected to the metal shell of that exposed battery.

In the end I was able to completely remove the terminals and their plastic frame by disconnecting the two mail terminals from the ends of the batteries and the small tab next to the heat sensor chip. They are all attached using what look like tiny spot welds and were easy enough to remove without too much damage.

The batteries themselves are plane with only BF stamped on them in ink

[Anonymous No.222276]

>>222252

The battery itself is labeled 1.3 Ah (amp hours). I have a 2 amp DC power supply, it should handle that without a problem right? Now I all need to do is make a circuit that will drop the voltage from 12 down to 8 and I'll be GTG. Sadly I have no fucking clue how to do that. Is a resistor all I need or something more substantial?

[Anonymous No.222300]

>>222276
>>The battery itself is labeled 1.3 Ah (amp hours). I have a 2 amp DC power supply, it should handle that without a problem right?
The amp hour rating gives you a clue as to what the expected draw of the motor could be, but it's not equatable to an actual figure for the average current draw at stall.

A 12v 2amp supply (24 watt) sounds a little on the weak side. If it's not enough you will simply be overloading and overheating it, and the drill won't have as much force at stall.

>>Now I all need to do is make a circuit that will drop the voltage from 12 down to 8 and I'll be GTG. Sadly I have no fucking clue how to do that. Is a resistor all I need or something more substantial?
That would be a big resistor in terms of wattage. If you want 7 volts at 3 amps from 12 volts 2 amps then you need 16 watts or more at 1.8 ohms.

[truckerfag !!xXmBuWkIT3n No.222340]

>>222276
Pretty sure this will work.

http://www.circuitdiagram.org/12v-8v-converter-lm7808-regulator.html

[Anonymous No.222390]

>>222276
1.3A is capacity

It can output power for 1h when output is 1.3A
i think motor input would be more like 2-3A

get multimeter and some wires and measure how much current motor draws at fulls speed, remember to give it some resistance so it doesn't just spin freely, then get power supply that gives enough current

(or you can get 3 of those DC power supplies and connect them in parallel to get 6A max output.)

[Anonymous No.222393]

>>222390
1.3Ah is capacity*

[noko No.222424]

EE here.

Ideally, get a decent transformer that steps the mains down to around 10-12V, rectify it and put some beefy caps on to smooth the waves.

Heck, you can also just get a buck DC-DC converter and run that off a car battery charger.

[Anonymous No.222532]

>>222424

I'm trying to go for something more portable, like a standard wall wart or brick on a rope type thing. I've looked at a few online stores be haven't been able to find one of those with the amps necessary to stand-in for the normal batteries. That said, I still don't know how much the motors really draw. I checked out some replacement motors but they don't indicate the wattage or amperage, just volts. As for running a much of wires into the handles of my tools, thats not gonna happen. The terminals are a minimum 6 inches into the tool and I have no way to securely attach them to the terminals.

[Anonymous No.223393]

Sounds interesting. I have a few older drills that use stick-type batteries also. Black and Decker mostly but also Makita. I've love to DIY a AC-to-DC code for them.

[Anonymous No.223800]

http://www.instructables.com/id/Convert-a-battery-drill-to-wall-power/?ALLSTEPS

[Anonymous No.224011]

>>223800

The problem there is he is using a 12v adapter on a 12v drill, so there is basically no work involved. That wouldn't work for the guy with the old 7.2 and 9.6 volt tools. He'd need a fairly heavy duty circuit, one that could handle several amps, to step down the voltage or he would blow the motor.

[Anonymous No.224022]

Okay, so I have a multimeter and I can use it to test the batteries. The battery says it provides 1.5 aH. So, do I just divide the multimeter reading by 1.5 to get the draw of the motor and shoot for that amount when looking for a DC adapter?

[Anonymous No.224123]

>>224022

That wont work IIRC. You'll probably find that the batteries output quite a lot of amps, much more than the motor will ever draw at once.

[Anonymous No.224348]

>>222182
>>222170

I always wondered... why do those newer keyless chuck drills still have that shitty key holder built into them? They dropped it off later models but the one if that pic still has it. I hated that thing. It was always clogging up with saw dust and wood shavings and then it would fall out in my tool box and get everywhere. Plus its a massive PITA to clean out. Just my little rant.

[Anonymous No.224353]

>>224348
psure thats for a spare bit and not for a chuck key bro, least that s what I use it for

[Anonymous No.224371]

>>224353

Nah brah, its for a chuck key. I have an old Makita 6012HD and its key fits in there like a glove. Not mine but picture related.

[Anonymous No.224388]

> I have no clue what these drills draw and the batteries max out my multimeter at 10 amps! I'm guessing a 2 amp DC adapter might cover it

I'm assuming the >10A reading is what you got from putting the ammeter across the battery. If so, dont ever do that again, shorting a battery is not healthy.

anyway, a 2A transformer will probably run a cordless screwdriver, but a 7-12V drill will typically draw 6 to 12A. you wont find a wall-wart that can deliver that.

for an 18V drill, it's quite easy to do, just use a power supply for laptops. 19V at 4amps should work fine.

for lower voltage drills, you might use a PC power supply for 4.5V or 6V or 12V drills. this is not ideal coz they are quite big. for other voltages, you probably need a custom made supply.

as for attaching wires, the simplest for me is to open the drill, and solder wires to the batt contacts. adding a power jack is also doable if there's room, but it needs to be heavy duty to pass 12A.

[Anonymous No.224396]

>>224388

My tools are 7.2 and 9.6 volts. The plan is to gut a few dead batteries (done) and fill the now empty cases with the gear needed to step down the voltage to what I would need (one at 8 volts and another at 10 volts) and finally drill a hole in the bottom of the battery and put a standard power jack inside it. This way I could buy one power adapter and just plug it into the "battery" that I needed and pop that into the tool. And since I wouldn't be messing with the tool itself I could still use them as normal cordless tools when needed.

I have been able to find some rather beefy 12v power adapters. It seems the are commonly used to power LEDs and stuff. I've seen several that claim to be able to output 10 amps at 12 volts. Like you said they basically look like laptop chargers. Thats plenty portable for my needs. Going with a PC power supply would just be too large and bulky to be useful.

How difficult would it be to make a voltage stepdown circuit that could shave 2 and 4 volts off a 10 amp power supply and still fit inside one of those battery cases? Since I've tested the batteries at full charge and each was well over its "rated" voltage I figured shooting for 8 and 10 volts would be easier then trying to exactly match the 7.2 and 9.6.

[Anonymous No.224402]

> How difficult would it be to make a voltage stepdown circuit that could shave 2 and 4 volts off a 10 amp power supply

building the circuit is simplicity itself, you just put as many diodes in series as needed. if you wanna drop 2 volts, you put 3 diodes, each having a 0.7V drop, for a total of 2.1V The problem is heat. at 10amps, the diodes will dissipate 21W.

since 21W of heat is a big problem, the usual way around this is to use a pulse-width modulator circuit driving a power MOSFET. If the PWM is set at 80% duty cycle, for example, then a 10V input becomes an (average) 8V output. and this setup generates very little heat.

[Anonymous No.224875]

>>224402

Do you happen to know of a forum or site where I could learn about how to make one of these? Or perhaps one that sells them? I did some searching but my google-fu is weak and I wasn;t able to find any that could hand 10 amps.

[Anonymous No.224991]

>>224875

I googled "pwm drill speed controller schematic" and within seconds found this: http://www.electronickits.com/kit/complete/motor/CKMX033.htm

for a DIY solution, I found this: http://www.electronickits.com/kit/complete/motor/CKMX033.htm

it's made for a 5A motor, but the MOSFET used can handle 23A, so I'm sure it would work at 10A. anyway, I have no time to look further right now.

[Anonymous No.225301]

>>224991

You posted the same link twice. Anyway, looking at that design I don't think its what I need. That is to say its more than I need and wont fit my application very well. I appreciate the help though and its gotten on the right path. Thank you.

[anus presley No.225493]

> You posted the same link twice

oh shit, the second link was supposed to be: http://www.circuitstoday.com/pwm-motor-speed-controller

if you do the search in Google Images, you'll get a ton of schematics, all functualy equivalent.

As for it being too big, it's true of the commercial unit, but when you substitute a tiny trimmer pot for the voltage control, and a smaller heat sink, it becomes positively tiny, with just one chip and a TO-92 FET, and also very cheap. The reason you can use a trimmer pot is because you only set it once to the desired output voltage (duty cycle), then use the drill's speed control for adjusting speed.

[Anonymous No.225840]

>>225493

Thanks again, I will look into it. Heres hoping that the local RS still carries this kind of stuff.

[Anonymous No.226097]

get a 9.6 volt powersupply.
the positive plug on a dewalt is always the one closest to the chuck.

[Anonymous No.226162]

>>226097

If you know of a place than sells a portable 9.6v DC power supply that can handle 10amps point me at it.