Cordless drill - Improving the battery

I hate it when my cordless drill gives up in the middle of a job. It seems that the supplied battery packs just don't cut it. So I opened up the battery pack and replaced the NiCads with much longer lasting NiMH batteries. Now I get a much longer use between charges.

Step 1 Disassemble the battery pack

My battery pack had 4 Torx screws (I later replaced with regular Phillips screws for easier access). Inside you'll find 10 NiCad batteries. They appear to be just a bit smaller than 'C' cells, and all attached together in series. 1.2 volts X 10 cells = 12 volts. The cells are marked as 1300 mAH which is why they don't last very long. You will probably want to photograph the arrangement of batteries since you will need to make a new pack look just like this. Also notice the thin insulator that keeps the top battery from shorting against the batteries on the bottom.

Comments

[ironsmiter]

Almost 6 years later, and still good information.

The one thing I took away from this, that i will be grateful for as long as I can remember, is the Soldering Video. That little trick/tip is going into the printed long-term storage

[MTtoo]

Ironsmiter, I need to pick your brain a bit. I have a stack, probably a couple dozen, batteries of various makes that I have "liberated" from a big box stores recycling box. One at a time naturally!! Most are 18 volts. My 18 volt charger is dead. Now to the question.....Would it be possible to use a 120 AC transformer that puts out 24 volts AC? Read on before you shoot me down. Put a bridge rectifier on the output to convert the AC voltage to DC.
The new transformer is a Honeywell 120/208/240V, 60 cy, primary to 24 VAC 40VA secondary. I am sure the 40 VA would take some time to charge a 18 volt drill motor battery. All of the instructavles I have read deal strictly with batteries. None mentions the care and feeding of the chargers. Care to share any helpful hints?
I am not a professional so I needed someone with brains to clarify my idea.

[ironsmiter]

wow, wow WOW... overkill.

Unless you're putting dozens of those cells in parrallel, 40VA is gonna DESTROY them.

I'll give you a summery of my research and calculations, as best I can.

Bear in mind, my power supply is going to be a 30 volt HP printer power-brick.
That brought my current limiting resistor VERY low ohmage, and wattage. 10 Ohm, and 1/4 watt.

Now, since you're starting with 40 volt...

The charging voltage is going to be approximately 1.4 v per cell.
You have what, 15 cells? (15 x 1.2 vdc nominal = 18 vdc)
So you need 1.4 x 15 = 21 vdc to charge.
24 v (supply voltage) - 21 vdc = 3 vdc voltage drop across the resistor.
Your cells are probably 2.5 Ahr. You need to charge C/10 , or 0.25amps.
R = E/I = 3 v / 0.25 = 12 ohms.
3 v / 12 ohms = 0.25 A
3 v x .25 A = 0.75 watts
I would upgrade to a 1w or eve a 10w resistor. they're only a dollar, and the added safety is worth it, imho.

You'll have to check VERY carefully. but if all the packs are NiCd, then 12-14 hours with the charger, and resistor described should give you a full charge. It should also be safe if you forget and leave it on a little too long. NiCd can survive almost indefinite charging at 1/10C rate. The extra energy gets converted to heat, and exits the battery through the cell wall.
Bear in mind, quick chargers like my original, have very sophisticated circuitry... but mine charged at almost 1C. it did shut off after that though, as a safety feature. Charge at 1C for 10 hours, and you better have the fire-department on speed-dial, cause around hour 3, it's gonna go Fwoosch!

Consider some googleing on "homemade NiCd chargers.
Tons of info is to be had at RC groups. they use packs much like these to fly their planes(though they're starting to switch over to li-po and li-fe)

Doh, just forgot.. you'll have to measure the ACTUAL voltage, under load, because you're gonna get a voltage drop over the rectifier. You're going to have to recalculate using the lower, measured voltage.

[MTtoo]

Ironsmiter, you must be an electronics engineer!!
I certainly appreciate your rapid reply.
I am not that much into electronics, and had to re-read your reply several times to boil it down to my level. I am more mechanical and my dabbling into electronics is fixing things broken. Determine what is bad, cut out the old and replace it with a like item. Your reply was a real insight in how to determine (calculate) the needed resistor.

An amazing bit of info can be had on these new-fangled gadgets (computers) if a person knows where to look for it. I wish computers had been available when I was young. I pre-date Television!!
Correct me if I am wrong, but this is what I determined from your reply.

18 volt batteries have 15 1.2 volt cells.
To charge these cells will require 21 volts @ .25 Amps for 12 to 14 hours for a full charge.
To drop the 24 volt output from the transformer, after it has gone thru the rectifier, will require a 12 ohm 1 watt (or better yet a 10 watt) resistor.
Now if I can just figure out the 40VA output of the transformer...Many years ago I have read how the VA is calculated, but it escapes me now.

I REALLY appreciate your thorough explanation of my question.
Have a GREAT DAY, WEEK, and YEAR

[MACSWAG]

Thank you so much for the very helpful post,I've just thumped one of my Draper 18v.bats on the deck and it is now charging,well the charger light is bright so I'll test in the morning,the other one same procedure the charger light comes on but quite dim , any more suggestions please or how to check which cells are duff would be helpful ,I'm in the U.K. so don't have the same suppliers as you chaps across the sea,

MAC.

[ironsmiter]

and forgot to mention...

Take your two packs, and rebuild one good one out of them.

With the now empty battery case, rebuild it will ALL fresh cells.
That should get you the best bang for your buck/euro/pound.
Keep any extra good cells for when, not if, WHEN, your newly repaired pack
kills another of it's cells. When you run out of THOSE spare cells... recycle all the old cells, and rebuild with new tabbed cells for what is now the third lease on life for that battery pack :-)

Now, we're 10-15 years into the future of your tool, and it's probably worn out. Time for a new cold-fusion powered drill.

[ironsmiter]

You don't need the same suppliers, for checking which cell is bad, just any old cheap volt/ohm meter.
As for buying the new tabbed battery cells... don't we all buy them from the same Chinese manufacturers?

Check the image in step three.
If the battery is freshly charged, that "light bulb load" is pretty important.
It helps bleed off the "surface charge" on the cells, and gives you a "working voltage" to measure.
Test the cell voltage after 2-3 min of running the light.


If you're "lucky" like I am...
I ran my batteries in a sawsall, till it quit sawing.
hen took apart the packs that weren't performing(one lasted less than 3 min of sawing)
When i took apart my Bosch 24V pack, most of the cells tested fine with the volt meter.
FIVE of them tested ZERO volts.
Guess which cells were bad? ;-)
This only really works if its a few bad cells, and you run the battery to "dead".
The down side is, if a cell is only starting to die, this may not catch it.

[jtobako]

is there a way to test the batteries individualy so that you could reassemble one working pack from several dead/dying ones? i have some (partialy) torn apart, some of the cells still hold a charge but others won't so i'm wondering how to identify good/dischaged cells from bad/dead ones. thank you

[klee27x]

Yes, you can use a battery tester or a multimeter to see which cells still hold a charge. But chances are extremely high that they are close to toasted. They won't hold a candle to the newly purchased cells, and they will quickly go into reverse charge when paired with newer cells, thus committing suicide. And all that time to rewire the pack was wasted. :(

[chenxinghao]

I have two bad Craftsman 19.2 volts EX batteries that when pluging in to the charger it will go GREEN and no charging to take place. The bolts seem to be the HEX type but my HAX drive could not go in. I noticed that there is a little round/dot in the HEX openning that is preventing the tool getting in. What type to tools to use to unscrew the bolts?

[bgentle]

It is a security screw that uses a torx screwdriver with a hole in the center. Take a punch and punch the round dot as you call it out or use a dremel too to grind it out then use a torx screw driver to remove the screw.

[Hubiewan]

Hi:  I have broken off the little pin inside the security screw, allowing your regular torx bit to work.  I do reccomend purchasing the security bit set from Harbor Freight.  On of them is cheap enough and quite extensive.  Hubiewan

[achollowell]

that is a security bolt I have see this type of bit at harbor freight

[crittergitter]

I find with my charger when it does that is to put the battery in the charger then unplug it and after a few seconds plug it back in. Hope this works for you.

[The Ideanator]

I've seen those, they suck. I'd do a search for special security bits.

[zappenfusen]

But in a pinch.

[frank farrell]

They are security screws or torques. Check with you hardware supplier for a set of driver tips

[nukemmcssret]

Get a drill bit a little bit smaller that the head of the screw and drill out the stripped screws. The head should come off both screws. remove the cover and there should be some of the screw exposed. You then grab it with a pair of needle nose and turn out the screw.

[Caspar]

Before the pliers bit, heat the screw head with a soldering iron tosoften the plastic.

[Sooner Aviator]

There is a great set of security bits available at harbor freight, steve's wholesale, and other discount type tool places for 10 bucks or less. Even ace has them, although you might pay more. they have all the security bits youll need, including tamper resistant hex (with the dot in the middle).

example: http://www.discounttommy.com/Shop/Control/Product/fp/vpid/3433762/vpcsid/0/SFV/32282

[jeff-o]

The battery packs for my cordless drill do that. Try plugging the battery into the charger, then unplug the charger from the wall. When you plug it back in, it'll start charging the battery (if your problem is the same as mine).

[edhalfdead]

You probably need a torx (star type) security (tamper resistant) bit. It can be found at Harbor Freight. A set of 6 is $5.99. Also check Napa Auto Parts, and I think Pep Boys. Snap On & Matco will have them too but you'll pay much more.

[eel_dahc]

I just redid one of my Craftsman 19.2 batteries. What I did was a little bit different. I bought an 18v battery pack from Harbor Frght (HF). It was a gamble really because I didn't know for sure how the batteries were arranged in the pack. Luckily they are arranged in the same shape, however they are connected differently. Luckily though there are wires already soldered and coming off of the pack that are long enough to make it work. My original craftsman pack had various bad cells. But, the cell connected to the terminals(the one on the top of the pack) was still in great shape. So, I snipped the nickel strip off the bottom( leave as much as you can though so when you solder you can hold the strip with pliers to sink the heat ) side of the top battery and the negative wire going to the rest of the pack. I then carefully pulled out the fuse/resistor wires making sure not to damage them. Then I soldered the red wire coming from the HF battery to the bottom of the cell with the terminals on it and the black wire from the HF pack to the black wire going to the cell with the terminals I then tucked it all into the craftsman battery case, put the top on, screwed it back and then charged it up. Perfect. If you do this make sure the battery with the terminals is still good. If it is not then you will have to replace that cell with a new one. Best of all, the pack cost $10, on sale for $12.99 with a 20% coupon.

[gsnoorky]

That pic looks like my 12V Sears Companion drill battery--I'm working on that now. It doesn't seem to work very long in the drill--a few secs, and it slows. I did do the battery starter trick--it was at ~10V--now, it's at 13+ V. I rapped it on the floor a few times and put it back on the charger--instructions say to leave it on for several hrs.--maybe even six.

I'm also working on my two Milwaukee 18V "Power-Plus" batts. Using the same trick, one seems now to be the usable battery for the drill I had loved--the drill turns solidly again! The other batt may be too far gone. It did go from 0V to ~3.2V, though. The charger doesn't accept it yet. I'm nowhere near ending the fight for it: I'll cut it open and go NiMH, if necessary.

Big box HW stores want $70-$80+ for such Milwaukee 18V batteries: Well, I then knew that the expensive drill screw wished to turn into myself! Amazon was somewhat more reasonable: $50+, yet, I haven't checked lately. Thus, I haven't used my originally priced $200+ drill for a couple of years. I was about to give up and purchase Skil or B&D--or even cheapo HFT or Big Lots!

(These Milwaukee batteries don't use the familiar vertical post most drill batts often use. Three side-shielded terminals "slide" horizontally into the drill bottom or the charger. As for checking such unmarked terminals for polarity, use a voltmeter to find the terminals which give a positive voltage reading--perhaps after charging. For this Milwaukee 18V "Power Plus" ni-cad battery, apparently the terminal on the far left (terminal side up and terminals facing you) is neg (-)--the one directly next to it, on the right, is the positive terminal (+).)

Thanks for the great inputs here!

[cjq]

Hi folks, I've read comments about re building 19.2 Craftsman packs, I still have a problem. I bought 6,000 mah batts with tabs . The pack is complete and has been charged . I had difficulty getting the charging to start. I found the "old" battery pack corroded real bad. There is a tiny circuit component ,a thermo device I think . I had to by pass thin device . I also found a "fuse" link ? I think it is ,and that was broken,I by passed that also. Now here's my concern,,the charger has a red lamp to indicate charging and a green for full charge. Upon initial incertion the green lamp lighted . I know the new batteries needed charging but the red lamp did NOT light. I left the pack on charge overnight and the batts have charged to 21.5 volts surface charge . After a little use the voltage dropped to 20.5 . How do I correct my charging difficulty. The battery pack had NO temperature rise overnight. I'm thinking the Batteries were in a trickle charge,,,make sence? I need some technical help Thank You

CJQ

[bricabracwizard]

I think if you want lots of answers post this question to the forum, hopefully you'll get an answer soon, sorry I don't know the answer.

[dcobrien2000]

I have a set of 18V Coleman tools that came with 2 batteries. A while ago one became hard to charge and finally the other failed. I could not find replacements anywhere so I was faced with buying new tools (lots of $$). I found this post and then the link about reviving rechargeable batteries, it said that crystals can build up in the batteries and short them out. As a fix it suggested hitting them with a blunt object. I opened up the batteries like this post suggests and then whacked the cluster of batteries firmly with a rubber mallet. To my surprise it worked, they now hold a charge and work great, no new tools!

[solaralternatives]

I wonder if that physical shock breaks the crystals like electrically shocking does. Anyone try this with an unprotected Li-ON cell?

[snet]

I recently ran a cross a Makita 6343D with 2 18v NI_CD batteries and a charger on one of the free auction sites. When I received the drill one of the batteries worked fine but the other wouldn't work at all, even though the charger showed it "charging".

I wasn't too concerned since this whole lot was FREE but after reading this I simply tried cleaning the metal contacts with rubbing alcohol and lightly wacking the bottom of the battery with the rubber handle of a hammer and POOF it started working again and holds a charge.

Thanks again for the great advice! =)

[fromjim]

I was about to trash a good Craftsman cordless drill because the batteries would not accept a charge, I was in the process of trying to find good replacement batteries at a reasonable price when I came upon this site, I tried the above tactic, whacking the battery pack hard several times on a block of hard wood, I then placed it in the charger and it began to charge, an hour later I had a fully charged battery, even the weak battery that would take a small charge benifited from this procedure.

Thanks a lot guys,

God bless

Jim

[crazyg]

i will try that:-)

[wupme]

Its always surprising how many technical stuff you can fix with whacking it. A wack actually fixed my digital preamp on wich an amp technican gave up... Its also a cool way to fix something.

[-max-]

LOL! i once fixed a camera with "lens error" by trowing it at a wall!

[jeff-o]

I'm delighted when the fix for a problem is "hit it with a hammer." :D

[PocketBrain]

You should solder to the tab; soldering directly to the cell can cause internal damage. Soldering to the tab will require less time to melt the solder, as it is partially isolated from the cell itself, and much less heating of the battery's internals.

[apeters7]

Does anyone know if you can put a 18v power tool battery on a trickle charger like a 2 amp slow charge. I have a schumacher battery charger.

[RangerJ]

A less expensive method is to replace only the bad cells. To find out which ones are bad, charge the battery pack. Let it sit overnight, then take it apart. Check the battery voltages with a digital volt meter.

Sub-C NiCd cells like in hte battery pack shown should be 1.2 volts. Mark the voltage on every cell. Most often, there are one or two cells in the pack that will read .9 volts or even less. Replace anything less than 1.1 volts - those too, if you have enough replacements.

Put your battery pack back together and it will work pretty much as well as when it was new.

Don't mix NiCd and NiMh or lithium ion batteries.

[dontknowsquat]

Anybody got the specs of the diode looking component in the battery pack of the 19.2 volt nicd pack?
The white rectangular 2 wire component in the battery pack is a thermal fuse rated at 115 deg C. I found some at ebay but have not ordered them yet. If this blows then you won't be able to charge your batteries. I shorted one so that I could charge my battery and it did but it got extremely hot so if you do decide not to replace the thermal fuse then attend the battery when it is charging. I think the diode component is a thermister. I assume it varies the current according to temperature and it seems it is not operating correctly since my batteries get hot when charging? Anyone know what is the maximum temp for the nicd's?

[dontknowsquat]

Found some info on the web. It would seem that generally, you do not want the NiCds going over 140 deg F. Batteries with a low charge and are charging will not heat up that much until they start getting close to full charge. I believe that is the principle that these chargers work on. They sense the battery temperature and should lower charging current according to rise in temperature.

[rc jedi]

One should never get batteries hot during the charge cycle. NiCad seem to tolerate it somewhat, but it surely lowers the life of the pack. The fast chargers allow us to charge at a higher current rate, but also allows us to ruin a pack. I am a model airplane flyer for 30 years and I have found the slow overnite charge seems to be the easiest on nicad. remember nicads self discharge, so we shouldn't leave them for months on end without charging them. they also like to be cycled. There are many reasonably priced chargers out there for just this purpose. This instructable is a good one, since we all wanted to see inside the pack. Maybe someone here will do one and make an adapter for lipo or lipoly battery so we can power our older drills with the new chemistry.