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Make your cordless tool hybrid with a power supply


nightmaim

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My english is awful, but I'll do my best...

This is a schematic to build an AC power supply to your cordless power tool. It will work with any 18V Ni-CD battery-powered tool. It will NOT work with any another voltage.

You'll need some experience with electronics, the internal inrush currents that we'll use are dangerous, also you can explode your battery and tool if something is connected wrong.

Advantages:

-Up to 1.5Ah. of extra power to your tool giving extra torque

-less stress and longer lifetime to the battery

-extended worktime

-lasts for all day if used intermittently

Disadvantages:

-your cordless drill becomes corded, but can still be used without AC power

-a box following you

How it works:

Once you plug this power supply into AC mains and in the battery tool the PS will charge the battery while the trigger is not pressed at a rate of ~140mA, which is safe to any Ni-CD battery from 1.2Ah to 1.8Ah and good enough to charge a Lead-Acid battery. When the trigger is pressed the PS unit will stop charging the battery and act as a auxiliary power, giving up to 1.5A extra to your tool. Automatically it will charge the battery again when the trigger is released. This charge mode, plus 1.5A of auxiliary power will result in a longer battery lifetime, as the battery will be less stressed overtime. Also, you can use as a overnight, it will take 14hs-16hs to get fully charged, depending the state of charge.

The components are cheap and easy to find in a electronic store.

You'll have to make a box for this components, it can be made from wood or plastic.

Parts:

1x 30V 2A Transformer (15+15V center tapped works too*) T1

1x 50V/10A Diode bridge (KBPC1010 or similar)                BR1

1x 50V/1A Diode bridge                        BR2

4x 35V/2200uF electrolytic capacitors                        C1-C4

1x 25V/3300uF electrolytic capacitors                        C5

1x 16V/100uF electrolytic capacitor                        C6

1x 35V/47uF electrolytic capacitor                C7

2x 0.1-ohms 3W resistor                        R1/R2

1x 1.2K-ohms 1/4W resistor                        R3

9x 18-ohms 2W resistor                        R4**

10x 120-ohms 2W resistor                        R5**

1x 270-ohms 1W resistor                        R6

1x 2K potentiometer                                        VR1

1x TIP41C TO-220 transistor (NOT TIP42C !!!)                Q1

1x 7824 linear voltage regulator                        Q2

1x 7812 linear voltage regulator                        Q3

1x Green LED 5mm                        LED

1x General purpose 24V >5A DC relay                        S1

1x 10A fuse                                        F1

3x Small heatsink

1x Large heatsink with fan (CPU cooler sold in any computer store)

*If you're using a center-tapped transformer then it should be 3A instead of 2A. Heatsink may be necessary.

Battery:

Most of you will prefer to attach a wire to the battery plugged in the tool to when using this power supply, so it can be easily disconnected when AC is not required or is not available. But if you prefer the tool lighter like me, or if you got a bad battery and need to buy another, or even doesn't have a charger because you bought a bare tool, consider use a Lead-Acid battery inside the supply unit. Lead-Acid batteries are heavier than Ni-CD, but are very powerful and much more cheaper than Ni-CD. For example:

3x 6V Lead-Acid Gel-Cells battery which can supply up to 4.5Ah, almost 4 times more than a 1.2Ah Ni-CD and costs about $10.00 ea., so, $30.00 to get 18V.

15x 1.2V Ni-CD C-Size 1.2Ah costs $3.00 ea., $45.00 for less capacity AND memory effect. Lead-Acid batteries DO NOT suffer memory effect. Only thing required is a 1 charge/month for 10-12hs to avoid sulphation.

This power supply works with both Lead-Acid and Ni-CD batteries with a simple potentiometer adjust. Ni-MH batteries may works too, but since they can't be left on the charger the cells can be damaged if left on the charger for too long. Lithium-based batteries are NOT suitable and may explode if used with this charger. If you got a Makita that uses Li-Ion and are interested in this guide, get some PB-Acid or Ni-CD ones, the tool to be modded is not the problem.

Tools:

-thermal grease

-silicone

-teflon tape

-masking tape

-screws

-A powerful glue

-A good multimeter

-Weld and iron

-wires AWG 20 to internal components and AWG 10 to the tool (if your battery is remote, otherwise, AWG 14)

Schematic:

18vpowertoolschematic.jpg

Power resistors:

**R4 and R5 must be arranged in a parallel mode, just like R1 and R2:

resistors.jpg

Heatsinks:

This is the large heatsink from an AMD with small heatsinks attached to the 7824/7812 (middle-right) regulators and the transistor TIP41C (left). The small heatsinks were stuck with a mix of 50/50 silicone and thermal grease:

heatsink.jpg

Cooling resistors:

Resistors have less resistance when hot making the maths a nightmare, this can compromise the precision of the charger, so I've attached them at front of fan:

hotcircuit.jpg

VERY IMPORTANT:

The body of transistor and the heatsink MUST NOT carry any current between them. It must be insulated and tested before use, otherwise it will burn the relay:

caution.jpg

All-In-Box:

Almost done, notice that I've use another fan in the transformer, that's because I got a bad quality transformer which is working overloaded at more than 50%. You shouldn't need this.

boxu.jpg

LET THE BATTERY TO BE PLUGGED LATER

When everything is OK, set the potentiometer to about 1000 ohms and power on. Measure the voltage between any negative and the hot wire to be attached on the battery, adjust your pot to reach between 22.2V to 22.4V for Ni-CD batteries and 22.1V to 22.3V for PB-Acid batteries. Let it for testing for about 30 min. and check voltages again. If everything is OK, plug off and connect the battery.

Safety:

Since we're working with DC voltages means that can't be inverted, or you can damage your drill. To plug the power supply with your tool/battery you can use those type of connectors, I don't know if they are easy to find in U.S., but any 2-pin or more plug that can't be inverted can be used:

wiring.jpg

enjoy  :)

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  • 11 months later...
  • 5 weeks later...
  • 7 months later...

Thank You Very Much believe me you are the only man so far that present a complete project solution for that issue.With so many bare body of a bare drill it is an one of a kind solution,but i want to ask you can safely someone use it with other tool as saw's or grinder that hold a lot of current when they start and during a job that you want to complete?

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I want to point out that should you do this, you will void any warranty you had with he tool, so I recommend doing this with older tools.  Also keep in mind that 18v tools are not built to handle the power of corded power, so you will be putting a lot of strain on the tool that it was not built to handle.

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I am going to be exceptionally honest here, I've searched and searched the internet and Nightmaim is probably the only person to ever go into this much detail on converting a cordless drill into a cordless drill.

Truthfully, I am not sure if I'd ever do this, but if I wanted to, I'd be sure to look at this guide.  Not too sound weird, but this is quite impressive and it's extremely and I mean extremely rare to find someone willing to divulge into as much detail as you had. 

Although I have asked this on another occasion, but another member named Framer spoke about a Dewalt AC Adapter.  Although this was months ago, I called Dewalt and by accident (it seemed?) mentioned this AC adapter.  Is there any information anyone could provide on this item? 

Maybe even a website/pdf file?  I'll admit, I am not thinking of actually buying it, but I couldn't find any information about this on Dewalt's website and the person I spoke to the on the phone made this item seem like it's a big secret or something.  Obviously, it's not a secret, but you can see where I am going with this.

I made a topic asking if there was a way to convert a corded drill into a cordless version, but all the information I have is that you need a DC converter and a 12 volt battery.  Mind you, I just would like to know to figure out this question once and for all as this is a question that is not as simple as I thought it would be initially. 

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KJONES:  Would you mind if I asked when the adapter was discontinued?  I realize this probably could be found very easily online or by calling Dewalt, but if it's been discontinued, it's likely been several years, maybe even more than that.  Why that is important is because the more years go by, the chances of finding someone who actually has accurate information also goes as well.

Only answer if you want to though, I am just asking because I wasn't even sure if you could even buy the adapter anymore.  I don't mean to make anyone feel as if they have to answer me though.

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No worries!  I actually do not know for sure when it was discontinued (possibly someone else on here will know, especially the guys who have been in the company longer).  DeWALT has a policy to support any discontinued product for at least 10 years after the time it is discontinued, so there should be no issues finding the product.  24v was before my time in the industry though, so I do not know a whole lot about it, other than the few tools that I still see a lot of out in the field (rotary hammer and recip saw).  Sorry that I do not have any more information than that.

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KJONES:  Would you mind if I asked when the adapter was discontinued?  I realize this probably could be found very easily online or by calling Dewalt, but if it's been discontinued, it's likely been several years, maybe even more than that.  Why that is important is because the more years go by, the chances of finding someone who actually has accurate information also goes as well.

Only answer if you want to though, I am just asking because I wasn't even sure if you could even buy the adapter anymore.  I don't mean to make anyone feel as if they have to answer me though.

The 24v adapter was discontinued in September of 2006. Model # DW0247.

24v tools, and the adaptor are still around USED and the batteries are still in circulation.

DW0247_2.jpg

DW0247_A2.jpg

DW0247_A3.jpg

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I hope this doesn't come off sound weird, but ToolGeek, you are quite awesome, no above awesome for posting pictures and providing extensive details.  Thank you very, very much.  I truly appreciate your hard work and the fact you took the time out of your day to post pictures of this.

You've been a giant help to me, that is seriously awesome that provided me with all that information. 

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  • 9 months later...
DeWALT has a policy to support any discontinued product for at least 10 years after the time it is discontinued, so there should be no issues finding the product.

Is this still policy?  The 24V adapter is discontinued and unavailable.  I also can't find anything for the 28V system and the Dewalt website disavows any knowledge of it :)

The "smart" battery packs in the 28V & 36V tools are the weak link for the entire line and will be an ongoing headache for users.  The pack electronics will "fault" with only 1 weak cell and then the tool or the charger will not operate.  The only solution is to replace the entire pack since battery servicers like Battery Giant won't work on these electronically-monitored packs.  Given all that, an AC adapter would be a solution to enable a customer to use his expensive top-of-the-line tools.  I wish Dewalt would make adapters for these platforms.

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