Introduction: Battery Adaptor for Cordless Tool

I had a whole set of 14.4 Volt cordless tools including flashlight, small circular saw and a drill.
First the charger went, then the batteries died, and then before I could buy replacements the company then switched to the 18V format and dropped all product support for the 14.4V line.
I purchased a new 18 Volt drill from another manufacturer in protest but it really wasn’t as good as my old one, the chuck slips when drilling and the drill clutch doesn’t seem to handle torque well.
So how to resuscitate my old tools cheaply?
I had two 18V batteries and chargers from other tools and when I jumped them to the 14.4V tools they seemed to run okay. The challenge then was to convert a 14.4V battery into an adaptor.

Step 1: Step 1 Salvage

Gut the battery, removing the NiCD batteries inside and safely recycle them. Salvage the clips off the battery that serve as the connectors to the Tool.

Step 2: Step 2 Solder Some Bits You Salvaged

Solder on a new wiring as needed for the clips

Step 3: Step 3 , Glue the Terminals Back In

Glue into the battery housing part that fits into the tool.
Note the polarities carefully!!!!!!
I use common plastic seals-everything glue as it’s also waterproof and serves as a good insulator

Step 4: Step 4 Solder in a Clip to Attach to the New Battery

Solder on a clip to attach to the battery. I used a piece I salvaged from inside an obsolescent cordless tool. ( they are good for something) and wirenuts to make sure nothing comes apart.

Step 5: Step 5 Cutting the Base to Fit the New Battery

Use the 18V battery as a template and cut out the oval from the bottom of the 14.4V battery case.

Step 6: Step 6 Reassemble and Glue on Something to Hold Them Together

Reassemble the 14.4V (no longer a battery) adaptor.
Glue on some salvaged hook and loop fastener strapping.
This pic shows the new battery clipped to the adaptor but not yet inserted

Step 7: Step 7 Insert Battery Into Adaptor

Connect the new battery via the clip and insert into the adaptor.
You may need to cut the hole a wee bit wider than than the battery's neck to allow the clip to pass.
Fasten the straps to hold it together

Step 8: Step 8 Polarity Check

Mark what side and what colour wire your polarities are on the adaptor so you don ‘t short out your tools by mistake. I have one 18V battery with the positive and negative the same side as the adaptor and one that is reversed......

Step 9: Step 9 Inset Into Tool

Step 9
Insert into your favourite tool!

Now you can get back to fixing all those things you said you’d get around to if you only had tools that worked.

I haven't run into any problems so far with the difference in the voltage. No guarrentees on that by any means. Matching voltages is preferrable but close will probably work fine. 14.4 and 18 might work okay, 9.6 and 18 will probably melt down but who knows......


trundlemurphy (author)2016-09-07

Hi ! Once you've fabricated the addaptor, you're replacement battery pack could be wired to a voltage closer to what's needed. Say 9.6v needed... take a 20v battery pack, open it up. rewire your batteries from series to series/parallel; if possible. It depends on what you find after you've opened the battery pack.

si.dixon1 (author)2015-02-26

electrics are black magic to me, but i have a 12v dewalt. reckon a similar approach is feasible...or is it too big a jump from 12 to 18?

burntbob (author)2015-02-07

Thanks! Hard to believe so many people have looked at this and my other battery hack instructable! Hope they find useful ways to keep old tools working.

russ_hensel (author)2015-02-05

Just a note to let you know I have added this to the collection: Cordless-Drill-Battery-Maintenance !


Take a look at a bunch of different/similar approaches to this project.

handydave937 (author)2008-10-23

I agree with dendave.joe, I have dropped my Milwaukee drill off the roof, off of ladders and abuse it on a daily basis. I also know for a fact that I can get any part for any of my Milwaukee power tools including batteries. It always pays to buy high quality tools

cj8675 (author)handydave9372012-10-14

yea me too with my dewalts

zappenfusen (author)handydave9372011-10-06

I've been using my Hilti hammer drill, Makita drills and impacts & Milwaukee sawzall for 15 years with a few battery pack cell replacements since I purchased them. Hilti, 20 years (corded) Sawzall also corded, 15 years, & Makita Li-on since I replaced my Dewalt Nicd 6 yrs. ago. I've got a Milwaukee 3.6 volt screwdriver which will do darn near everything the Makita will do and is my most used tool. I'm an Electrician destructing, drilling, and screwing for a living. Handy Dave's philosophy is undeniable. You truly get what you pay for and if & when they go down they'll survive homemade batterie's, alternate power sources and an infinite variety of DIY repairs. The additional cost is more than negated when you have no complete tool systems being tossed in the dustbin. My wife doesn't get it or approve but if I allowed her to purchase I'd be pitching Ryobi's once a month.

mykiscool (author)2012-07-20
finton (author)2008-09-16

Wyle_E suggested (Jun 19)that "You could make a similar adapter ... to run portable tools from a car battery." I tried that with my 12v Black&Decker;, but disconnected it REALLY quickly when smoke came out of the drill's vents! Why would that happen? 12v car battery, 12v drill... Has anyone successfully done this?

XboxModz (author)finton2012-06-21

Yes, the drill was 12v and the battery should have been 12v. The drill overheat could have been cause by one of two things:

1. As someone else here mentioned, car batteries vary in output voltages slightly. The battery could have had an output voltage slightly above 12v. OR...

2.The wire you used to connect the car battery to the drill was too thin. That drill is going to draw 12v at around 2 amps, (depending on the drill). For this reason, I would guestimate you should use a wire no smaller than 10 Gauge, for both positive and negative leads. If the drill was unable to draw the current needed, this would cause either a voltage drop or increase (can't remember which right off hand) either of which means death to the drill.

coolguy (author)finton2009-01-29

Cars don't put out a consistent 12v. They can jump up or down depending on how fast the alternator is turning. You if you try to use auto power, measure the voltage first (using a multimeter), build a voltage divider circuit, and filter the input power to protect from irregular voltage spikes.

amclaussen (author)coolguy2012-03-16

FOR THE BENEFIT OF QUITE A FEW... Lets put it clear and more or less complete.- Understanding the most basic law of electricity and electronics can help a lot when you want to use electric motors and almost any kind of stuff. The OHM law is not difficult to understand. Imagine a piping circuit instead of an electrical one, that will help a lot. The amount of water that can flow thru a partially open valve will depend on how high the water tank is above the valve, but also on how big the diameter of the pipe is, and how open the fawcett valve is. The VOLTAGE of the circuit source or supply is akin to the PRESSURE of the water inside the piping (think PSI), the CURRENT is akin to the FLOW or quantity of water that flows in a given time (think GPM), and the RESISTANCE is akin to the friction loss or PRESSURE DROP of the piping circuit, either with a pipe that is too small or a valve that is almost closed. Now, using the unit system, the voltage is measured in VOLTS, the current in AMPERES, and the resistance in OHMS. This way is all too easy to fully understand and even predict how the devices will work when the power is applied to the circuit: Let's say we have a car battery with a nominal 12 volts (in reality it could have as few as 11 volts when almost discharged, to a little above 14 volts, when fully charged ans just recently disconnected from the charger!).

If we connect an electric motor, a small one, it will allow  just a fraction of an Ampere to flow through it, say 250 milliamps or so; because the small wire that is used in the windings will present a comparatively large RESISTANCE of about 48 Ohms.  BUT if we connect a much larger motor, like the Starter Motor of a car, the same 12 V battery will flow a large current, maybe 150 Amperes! because this motor presents a much lower resistance, of around 0.08 Ohms... (its windings are made with a much larger wire gage, just look at the diameter of the car battery cables!).

POWER is the result of multiplying applied voltage times current, so that a WATT is produced or dissipated when a current  of one Ampere flows pushed by one Volt.  Therefore, power can be calculated from the following simple relations:

I = V / R, V = I x R,  R = V / I...    P = V x I  or  P = (V) squared / R

In the case of our friend FINTON above, the small motor must have been defective, most probably having some shorted windings.  This resulted in a too small resistance that caused that the large capacity 12 V car battery  able to deliver several amperes and quickly burned the poor small motor.  If the motor would have been in good condition, it would run perfectly under the light load meant for it.  At the same time, that small defective motor would turn at partial speed when connected to an smaller voltage battery (say, a common 9V alcaline cell), but that small battery would be incapable of sustaining its output voltage when connected to the partially shorted motor, thus not being cappable of burning it!

Now, most DC (direct current) electric motors can be fed with a higher voltage, above the nominal one it was designed to handle, but  it is a matter of how heavy will it be loaded when operated.  See, the motor presents an electrical load that DEPENDS on the MECHANICAL load it has to move, so that if lightly loaded, common electrical motors certainly can handle say 1.5 times the nominal voltage, if the mechanical load is not far above the design one.  Present day Model Airplane hobbyists use motors designed for say, 12 Volts, with battery packs that can sustain almost double that voltage, but they use it wisely, using the maximum power for brief periods of seconds, like for Take-Off or maneuvers, backing off the electronic throttle to avoid burning the motor.  As this INSTRUCTABLE says, it is "safe" to assume that a Cordless Hand Drill meant for "12 V" nominal, can be perfectly run with a 14.4 V pack.  It will turn faster and will be capable of more power output, BUT WILL ALSO OVERHEAT more quickly if the same Load is applied, so keep this in mind and avoid loading it too much.  BTW, rechargeable cells have an actual voltage that is NOT the nominal one under load, so that the 12V pack is assembled from 10 1.2 V nominal cells, that maintain close to 1.0 volt under load each wired in series, and the 14.4 V pack has 12 such cells, thus achieving only 12V under load.  This applies to Nickel based cells. Lithium cells have 3.7 to 3.8 nominal Volts, so that one can perfecly use a pack of three to four Lithium-Ion or Lithium Polymer cells for that drill, saving a lot of weight and bulk, but then would need a special charger designed for Lithium cells, and also apply ALL the cautions of using Lithium cells!  Good Luck. amclaussen.-

finton (author)coolguy2009-02-02

Oh, OK. In my particular case the car wasn't running, but your point is good to know for when the situation arises. Thanks. Oh, and Criggie: I didn't have the battery in the drill when I tried running it off the car battery. As it turns out, the charger was defunct: the replacement I bought also didn't work! I gave the hardware guy my drill, battery, and the new charger - I just got them all back today with a charged battery, so I guess we'll see if the chargers are at fault or I have a problem in my workshop wiring...

11010010110 (author)finton2008-10-03

The NiCD batteries of the drill have more resistance than the car battery. When you run your tool off NiCD it actually gets less than 12 V (the rest is lost in heating up the battery) The car battery has low resistance so the tool gets really allmost all the 12 V You can add something with few ohm resistance in series to the car battery to simulate the resistance of NiCD's. Heat wire from electrical heaters is good for this. Expect it to heat quite much

finton (author)110100101102011-06-06

Hey 11010010110, I know it's over two years later, but what significance is the number 3372 to you? (your binary username in base 10).
Still haven't got around to trying your idea with resistance... :[

Sarah86 (author)finton2009-02-26

hmmm. well the car battery has 12 volts sure, but it can deliver 80 ampere so its about 200W of power. Sure, that enough juice to burn any electronic component.

chrwei (author)Sarah862010-09-16

that's not how amps works. amps are simply available, it's up to the load to pull them. Your typical home outlet provides 15 amps, but plugging in a .5amp cell phone charger doens't explode anything.

DallasDeckard (author)chrwei2010-10-30

This is true, but your example isn't really correct. A .5 amp phone charger outputs .5 amps, that doesn't mean the charger *requires* .5 amps from it's source or that it passes on a higher amperage to the phone. The amperage from the socket doesn't pass directly through the phone charger (or shouldn't). If it's stated amperage is .5 amps, it outputs .5 amps (or should) and no more.

You are right though, amp rating is simply what is available, it's up to the load to pull what it requires. Too many amps won't damage anything unless the voltage isn't fixed. Some (cheap) stuff can increase voltage when the current requirement exceeds it's amp rating, which could damage a device, but it's unlikely.

The voltage output of a car battery can vary slightly, up to 14 or 15 volts. It would only be this extra voltage that may damage the drill.

The problem you had could be the wiring. The motor may have drawn more current than it's wiring could handle.

chrwei (author)finton2010-09-16

this was at idle or under a load? it could be that the motor itself also had a problem and was trying to pull more amps than it should have. Black&Decker's tend to have "lowest bidder" parts in them, which is why your chargers keep failing.

criggie (author)finton2008-12-24

Yes - I used a 14.4 V drill and connected 15 metres of cable to a pair of clamps. Great for using out in the land rover, and a lot more efficient than an inverter+mains drill. The long run of cable induces quite a voltage drop too - the drill only gets around 11.5V Also remember the charging voltage of a car battery is around 14 V, so running the drill with the car motor going is likely to provide a slightly higher voltage than when the motor is stopped.

finton (author)criggie2008-12-25

Thanks for the reply criggle. Good to know it is already being done. Hmmm... I could make an adaptor for the drill, and one for the car battery, such that they could be connected by various length standard extension cords. Oooh! The extra resistance suggested by 11010010110 could be variable at the drill adaptor(a potentiometer?)to accommodate various lengths of extension cord!

criggie (author)finton2008-12-26

My drill was heading for the recyclers anyway.... Make like a plumber - "Suck it and see" how it goes. You won't damage the battery unless you short it or flatten it. Was the drill working before the battery died? Could it have been some old grease or lithium lube across some contacts? Or maybe its a cheaper build and the components couldn't cope with the current.... Mine was a fairly expensive bosch (thanks dad)

finton (author)criggie2008-12-27

The drill and battery both work, it's the charger that doesn't. No grease, but I did squirt a bit of CRC (non-conductive thin lubricant, used to remove moisture from electrical components, among other purposes) down the charger as the battery was very hard to get out. As the charger worked for a long time after this, I would be surprised if that was the problem, but I'm not pontificating. I went to Dick Smith's (Australasian electronics supplier) for that "pot" today: the bloke was of the opinion that even a short length of wire should create enough resistance, but explained that some drills have a four terminal arrangement where the first two are part of the switch arrangement for the main battery capacity - in other words I had bypassed this and was feeding the car battery straight into the drill. Haven't checked the drill for this yet...

cj8675 (author)2011-12-23

you have a kinda junky drill. you should spend the money on a dewalt because ive had mine 6 years and also dont change the battery design. i drop mine off 24 foot ladders, into water on side walks and etc. buy better tools
i had a ryobi and i dropped it off a 6 foot ladder onto the sidewalk and it smashed into a billion peices. now i only buy high quality tools.

burntbob (author)cj86752011-12-23

Everyone is entitled to their opinion and no one is forced to reycle their tools or battery systems. I salvaged my old reliable tough as nails and never let me down drill by using any rechargables I inherited or came accross partially for the fun of it but also that short of buying several hundred dollars of new drill this one did everything I needed,. I've pushed it hard doing heavy work sistering up floor joists and its worked just fine no matter what. May look junky but I prefer to think of it as mad max meets steamounk survivalist....

cj8675 (author)burntbob2011-12-24

ok sorry

Celtic Davey (author)2008-10-03

not a bad way to make use of an old tool but does the balance not feel a bit off with a heaver battery lower down on your drill/jig saw/circular saw?

burntbob (author)Celtic Davey2010-09-18

The whole contraption does hang down a bit further but doesnt seem any heavier. I find cordless tools a bit bulky at the best of times, but when doing all my latest project drilling and screwing beams together I still was able to get in where I needed to...

burntbob (author)2009-03-10

I'm sure my whole hack would frighten the original designer and their riskmanagement team to bits but as long as you keep the voltage relatively close, i.e. one order of magnitude up or down i.e.a 12v on a 9.6 motor, or a 18V on a 14,4 it should be close enough to at least try with relatively safely and should work okay. I'm using my old drill for some heavy duty screw fastening when I sister up joists in my place right now and it doesn't seem to be suffering at all. And the old battery is like a sled dog, it lives to work hard and works better for it. Sure you get the odd ozone-y wiff now and then but she keeps on ticking and no melt down or battery overheat, short, flames or sparks so far. I wouldn't try a 14.4 tool and a 28 volt except under test to destruction overclocking scenario just for fun, maybe at a safe distance just to see how long it'd run before critical mass and meltdown.

smessud (author)burntbob2009-10-03

Just to ramble. "one order of magnitude up or down i.e.a 12v on a 9.6 motor" This is not one order, one order (10x) would be 96V. You are roughly 30% above rated voltage. That is you are dividing its lifetime by around 4 to 10. You should be more careful (may be I am dramatizing) with the blade that has a limited centrifugal resistance and could break under stress, especially low quality blades.

burntbob (author)smessud2009-10-04

By one order I meant one rechargable tool voltage type as a rough suggestion. So far it's worked quite well in the year since I built the adaptor and still outdrills out screws the newer 18V rechargable I bought. I used it too when sistering up my basement rafters recently and I was pumping in heavy four inch screws and it held up great. I also recommend using good bits and blades, cheap stuff just dulls too quick!

chrwei (author)burntbob2010-09-16

a good drill will have its motor slightly oversized and so the motor itself would handle it. A cheap drill might actually have the motor undersized already, and certainly will have the cheapest gears to get to past the warranty. If your drill has lasted several years past its warranty already and isn't sloppy or making funny noises then it'll probably do just fine at some higher voltage. Do this to a cheap drill and you'll probably flatten the gears first.

The ozone smell is most likely due to overheating the motor brushes. Do it too much and you'll burn out the commutator, ruining the motor. Depending on how nice a motor it has, you may be able to replace the brushes with higher quality ones that won't overheat so easy.

As for drills and blades, using ones made for AC powered drills will always be fine for battery powered ones. AC drills pretty much always run at higher RPM's than battery.

As for "order of magnitude", this phrase has a specific mathematical meaning of "ten times". Using it to mean anything else will mean that people misunderstand you. Using it mean "one step up" is like saying run when you mean crawl.

Unclegene (author)2010-09-16

I had a charger go bad - went through my left over computer equipment power supplies and found one with a 24 volt AC output, got a bridge rectifier from Frys for 5 bucks and back in business. On this lash up, don't leave it unattended connected and monitor temperature.
On over voltage operation, I am running an 18 V drill on 24 volts and it is spry, but I watch for overheating and understand the commutator might go out quicker.

burntbob (author)2010-04-15

The drill is still running fine on 18V and I've  posted a second hack on how to build an adaptor for the newer type of 18V batteries that I got with another set...enjoy and keep on experimenting!

sukhbinder (author)2009-03-10

One should avoid increasing the battery voltage of a power tool as the motors are specified to work at the particular voltage. If you have a look at the motor used i cordless power tools you'll find that they donot have much coil windings but the coil wire is quite thick. so the motor generates the power by using high current and not voltage (which is the case for motors which have a large coil windings but with fine coil wire). if you increase the voltage the motor cannot extract as much current and will not perform to its capacity and the battery discharge will me more. Never change a NiMH or NiCd battery with a lead acid battery, the internal resistance of the lead acid battery is very low and the excessive current will damage the motors commutator and brush system. You can use a NiCd or NiMH with higher current rating (AH) but the same voltage as earlier so you'll have more back up or operation time available

ProfessorJWN (author)sukhbinder2009-08-28

Well, sometimes. Power wheels kids cars for example. These run at 12v, but the motors are 18v and will runat 24v with an electronic controller. In fact if the motors use and electronic speed controller, that likely would be the "limiting factor" and the source of smoke. I believe these are an H-Bridge and more than likely are made for the particular voltage of hte batteries.

sukhbinder (author)2009-03-11

The smoke coming out from the drill vents as mentioned in fintons post is most probably generated by the drills commutator and brush assembly. due to the very low internal resistance of the car battery it can source a very high current for an instance which is enough to fry the drill motor windings and the commutator brush assembly. Usually car battery have ratings of about 12V@35-40AH (current rating can be more depending on the vehicle). The AH rating means it can put out a current of 40A for an hour at 12V, so just think of the peak current it can put out in 1 sec (40x3600=144000A).
in a vehicle the part that uses the most current is the starter which is a high power dc motor, vehicle batteries have a spec called the CCA or cold cranking amps thats the current it can put out when starting the car. usually car batteries have a CCA rating of 300-400A. thats why the mechanics use such a heavy cable for jump starting your vehicle from another battery (the thick cables have very low resistance to allow for the large current to flow, else instead of starting your vehicle the cables would be burning)

alanis91 (author)2009-01-27

any ideas for an adapter to run 18 v tools with the house current outlet 110 AC

dendav.joe (author)2008-06-24

Ive had my Hilti drill 8 years. Its been in swimming pools, dropped off roofs and abused endlessly. Its as good as new. Pay a bit extra for a good quality drill, but the big money goes on the battries. Dont be seduced by voltage, its the a/hrs that count.

11010010110 (author)dendav.joe2008-10-03

Its W/hrs that count

1 W/hr = 1 V * 1 A/hr

panstar1 (author)2008-09-10

This might be a little off topic ,but the person who said ni-cad's are good for power tools because of there ability to put out large spurts of current. As a matter of fact ni-cad's were used to start aircraft engines I think they used them to replace the older lead acid battery's in radial engines (after a good cleaning repainting and complete removal of all acid from the lead acid battery the acid some how screws up the ni-cad. There best use is with small gas turbine engines like helecopters have. The engines have to spool up to about 50% before and fuel is injected & these starter's draw something like 1,200 amps ! I would like to see a li-ion pack do that !

selvol (author)2008-09-05

Good idea. I thought of the same thing a few years ago. My problem was I had around 10 different brand drill. Some Slid on and some had the pole in the middle. Glad to see someone made the idea. Regards

Derin (author)2008-08-25

whoa,i see an aerosol can of propane in the background

Derin (author)2008-07-09

I hate wire nuts!Use butt splices its a lot easier

Derin (author)Derin2008-08-25

rant not directed at u,just ranting the *cough* wire nuts *cough*

dsandds2003 (author)2008-06-26

I usually watch the rummage sales for them unwanted tools. I get them for next to nothing. I have used the DC motors for a couple wind experiments and the batteries are used to repair battery packs or charge them up with wind/solar to use on other projects. It is cool idea to reuse these packs for repowering.

FireBAT (author)2008-06-20

Very nice work! I have a Craftsman 18V drill that has good batteries, but the charger died. Since Sears changes the design of their battery connectors apparently every 6 months, the "UNIVERSAL" charger I bought won't work, even though the plugs are the same shape. I'll have to try this with my other broken drill.

austin (author)2008-06-19

god nicads piss me off, i wish they would just switch already, but i guess its profitable for the consumer to buy new batteries.

jongscx (author)austin2008-06-20

Well, NiCads are better for power tools because of the quick spurts of high-current that are needed when running something like a drill or circular saw. NiMH are a better chemistry, but aren't as durable and more prone to damage from fast-recharges... And ATM, Lithium is still a wee bit expensive. I think it's b/c of the complex/delicate charge controller

Mr. Rig It (author)austin2008-06-19

Ryobi has switch to Lithium now 2x times the service and mildly pricey

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