Drill Battery Pack rebuild

[BigMike]

So, i have a couple questions reguarding the battery pack in my 9 year old Dewalt 14.4v cordless drill that no longer holds a charge to drill more than 2 - 4 holes.

I have access to a few Laptop Li-Ion battery packs, but they use AA cells instead of the C cells.
1. Would this cause any problems other than shorter run time?
2. Could i put aditional AA cells in to get longer run time?
3. Can the current dewalt charger recharge Lithium Ion AA batteries?
4. Anything else i should be wary of?

Thanks,
Mike

[Joe H]

I would stay away from the lithium ion batteries. If you can find some nicad or nihm batteries you should be able to do this with no issues. The lithium ion batteries can be dangerous, they require a special charger and batteries have a pc board that regulates charging and discharging. If things get out of whack a chain reaction that results in the battery exploding can happen. Remember the exploding Dell laptops?

[MoonRise]

AA cells would most likely NOT be the cells to use, no matter what kind of chemistry they are (NiCad, Lith-ion, etc). Too much voltage sag under the high loads of a drill, and not enough amperage capacity for the high loads of a drill under load.

Yes the battery packs are (usually) rebuildable, I just had a bunch rebuilt. A chain in my area is BatteriesPlus, they rebuilt them. So far, so good.

Or if you want, you can (usually) get the (right-sized) plain cells in the appropriate chemistry for your charger and then stack-n-wrap and solder-n-weld the cells into the appropriate physical and electrical configuration.

As to your current charger being appropriate for lithium cells, most likely not. Easiest and safest rebuild option is to stick with the original cell chemistry and have the pack rebuilt.

[DSW]

I've got several rebuilt batteries for my old 14.4 Dewalts. I forget where my old boss got them from now. I've picked up one or two "generic" battery packs that fit my Dewalts from a local tool supply house at about $40 a piece or so last winter. I also watch the chain stores when the discontinue tools. I've nabbed a few tools just for the battery packs, displays/ discontinued merchandise, when they mark them down stupid cheap to blow things out before inventory.

Lately I've been upgrading everything to the 18v's from the old 14.4's. I had a tough time finding the saws to match my 14v's so ended up getting the 18v units. Now the selection on new 14v tools is slim. Want a grinder, jig saw, drywall tool and your only option is the 18v's. It's almost often cheaper to get the drill with 2 batteries and charger (especially if you can get good deals on close outs), than it is to get 2 14.4v batteries for tools that are 10+ years old. I prefer the lighter weight of the 14.4's, but since Dewalt just doesn't support the line well with new options, I'm stuck moving up to the 18V tools.

Too much of a PITA to keep two different sets of batteries charged. It's a shame my old original 14v drills would accept the 12v battery packs as well as the 14v ones. Where I used to work most of the guys had the 12v drills, I could grab any battery from their charger and slap it in my 14v drill if needed and it would run almost as good. The newer drills Dewalt "fixed" that problem and the other sizes don't fit.

[weldbead]

the dewalt tools work good, but over the years ive had 2 or 3 of the 18v batteries fry. as you say its cheaper to buy a paackaaged drill with 2 batteries than to buy 2 batteries.

[Boostinjdm]

The size you want is "sub-c" in NICAD. Nimh cells work too, but you have to buy the correct Dewalt charger. It's all yellow. I forget the model number. Rebuilding packs is easy if you have the ones that are screwed together. Cells are currently about $2-$3 each so you are looking at $24-$36 in cells for one 14.4 pack. I think the original cells in the Dewalt packs are 1400 or 1700 mAh, but I don't remember for sure. If you buy new ones, look for 2000-2400 cells to give you an increase in run time.

[BigMike]

Where would i get the batteries, do you think Radio shack might have them?

I have more time than money right now so doing a rebuild is the best thing for me. I'll take a closer look at the packs tonight so see exactly what they are and if I can easily open them.

Thanks for all the input guys. I'll forget the whole Li-Ion idea.

Mike

[MoonRise]

Where to get the cells? (a battery is a collection of cells)

Are you new to this internet thing? Search man, search.

Hmmmm, maybe here ... http://www.batterystation.com/nicads.htm

Or http://www.batteriesplus.com

and from there you can go to

http://www.batteriesplus.com/models/...es/Dewalt.aspx

Or search for 'battery' and 'dewalt' and your drill model number.

[fredf]

MoonRise: You should look for tabbed cells. If you solder directly to the cells, you may cook them! see the note on the top of the page http://www.batterystation.com/nicads.htm. tabs are spot welded on the cell.

[MoonRise]

Originally Posted by fredf

MoonRise: You should look for tabbed cells. If you solder directly to the cells, you may cook them! see the note on the top of the page http://www.batterystation.com/nicads.htm. tabs are spot welded on the cell.

pssst, Fred,

I'm not the one trying to build/rebuild a battery pack.

And for those who don't KNOW how to do it, you do have to be careful when building a battery pack. Heat is not good for batteries, and to weld (do NOT-NOT-NOT weld a battery unless you KNOW what you are doing!!!) or solder (you still have to know what you are doing to solder a battery pack) you have to apply at least some heat. Too much heat or for to long in the wrong place and you melt some internal parts of the cell and make a mess of things.

The cordless tool battery packs that I am familiar with and have seen do not use tabbed cells, except -maybe- for the 'end' cells that the wiring connects to. The other cells are stacked and soldered in the appropriate physical and electrical configuaration.

[Boostinjdm]

Actually fred, you want cells with only one tab for dewalt packs if you can find them. Due to the positioning of the cells, the tabs have to run at all different directions.

[Boostinjdm]

Hey, look what I found.... A battery ready for a rebuild. Notice the screw holes on top. If there isn't screw holes don't bother, I've tried that before.

[steve45]

There are people on Ebay that rebuild battery packs. There are a bunch of online vendors that sell the individual tabbed cells. Lithium ion cells are a little harder to come by, but you should use the type of cell that was in the battery to begin with.

[boatbuoy]

you could also try to zap your old battery ---http://www.youtube.com/watch?v=PzIlVLOH9XI

[jbman45]

I've rebuild packs for years, so here's the secret but don't broadcast it too much or you'll shorten my supply!

Most packs, dewalt, ryobi other are screwed together so just take them apart. after you try to charge the pack, take it apart and check the voltage on each battery, it should be about 1.25 volts but you'll find one or more that show zero. these are the bad guys and mark them.

yes, get some new batts but I don't buy new ones. I usually go to home depot or some other recycle place and look for their recycled batts and take home some. checking those returned you'll find some good batts, use those to replace the bad ones in your pack.

next it doesn't matter on the tab configuration, just keep the overall pattern the same. use then extra tabs you pull off or some wire which is fine....but, nicad batteries are a big heat sink so you need a 250 watt soldering iron at least. you need to quick solder the batts and better yet go to your weld shop and ask for some of their low melt solder. I buy it locally in a pak and it's really neat to join dissimiliar metals. does a clean solder joint on the batts.

also watch for sales, I bought from tractor supply about 8 brand new battery packs for their discontinued drills. paid 2 bucks a piece for the packs, who cares what they fit you take them apart and make up new dewalt bat packs.

anyway, go for it; far better than the 60 bucks a piece they want.

[steve45]

Good idea, jbman45!

[jbman45]

Also, forgot to mention in my post...for those who really don't want to do this yourself I understand you can have your pack refurbished with new batts at Battery Plus stores. Supposedly they use a slightly larger capacity (same size) battery which may even last longer than OEM stuff and understand they are a bit cheaper as well. So worth a check if you don't want to do it yourself.

[Rick V]

Let me add some of my 'secrets' to those provided by jbman45.

I've had three different drills of the 14.4 volt variety. I've rebuilt their battery packs a few times.
Like jbman45 said, it is usually just one or two weak cells than need to be replaced.
I used to shop for discontinued, clearance or super-cheap sales on drill batteries - didn't matter what kind. I'd tear em apart to get the individual sub-C cells to use in repairing my existing battery paks.
An important experience lesson gained here:
Quality batteries (e.g. Canadian Tire) were 'Better' than cheapies (e.g. Princess Auto).
'Better' =
a) larger capacity (say 1.5 amp-hr instead of 1.2 amp-hr), and
b) more reliability (in the cheapies, 1 cell in 12 would be weak to begin with and another 2 or 3 would fail within about 8 recharges.)

However, this 'get soldering' thing gets to be a running battle after a while! Of the 12 cells in a 14.4 volt Ni-Cd battery, eventually they pretty much all get so weak they need replacing. It is a pain desoldering the cells and soldering in better ones - got to use an acid flux on the steel tabs too. No one mentioned the joys of a short circuit!

I'm preparing to go a new route entirely - see picture 1.
I'm going to replace those ~1.3 amp-hr sub-C nickel-cadmium solder-tab cells entirely.
$3 buys three plastic holders for 4 AA-cells. Three of the 4-AA battery holders fit nicely inside a standard 14.4 battery case. I'm going to use standard AA 2.5 amp-hr nickel metal hydride batteries - that are available just about anywhere.

AA Advantages:
1 - Should one cell fail, I can just pop it out and drop in a nice new one - no soldering!
2 - I get twice the running time from 2.5 amp-hr cells compared to 1.3 amp-hr sub-C cells.
(Sure you can get 2.5 amp-hr sub-C, like Milwakee, but big $$ and big weight.)
3 - It's 2/3rds the weight (30 grams per AA cells versus 45 grams per sub-C cell).
4 - It can be cheaper; I got a super-hot deal on a bundle of AA 'Energizers' at $1.60 each.

By the way, in my experience, all 2500 ma-hr (2.5 amp-hr) nickel metal hydride batteries are not created equal - see picture 2. I've had good performance and longevity from 'Energizers' but not so with 'RavoVac' - 2 of 4 went low voltage on me after three recharges. Maybe I just got a bad batch... but still, I didn't need that.

So add that to the mix.

Rick V

[Boostinjdm]

Going with smaller batteries = less run time. Also, most chargers do not like Nimh cells unless stated so. They tend to get a little toasty...

[Rick V]

Going with smaller batteries = less run time. Also, most chargers do not like Nimh cells unless stated so. They tend to get a little toasty... Boostinjdm

Well it's logical that a cell (AA) of 2.5 ampere-hour capacity will run longer (2X) than a cell (sub-C) of 1.25 ampere-hour capacity. It’s ampere-hour capacity that counts, not physical size.

As far as the chargers go, I can’t comment on specifics but the charge characteristics of the nickel-cadmium batteries are not very different from those of nickel-metal-hydride batteries.

However, I gave up using the manufacturer’s supplied chargers a long time ago. Why? Such commercial chargers cannot correct a commonly reoccurring problem – the lazy cell. In a 14.4 volt battery pack of 12 cells from an electric drill or even a 3.6 volt battery pack of 3 cells from a portable phone, one cell may get reluctant to charge at the normal charging voltage/amperage. The lazy cell(s) can be detected and ‘fixed’ if you have the ability to repeatedly totally discharge the battery pack (I use a auto H4 bulb – draws about 7 amps) and then recharge for a few minutes at low current while observing the voltage rise across the battery. I use a variable voltage/current power supply that displays volts and amperes. Set to the same voltage as a commercial charger but with a smaller amperage (say 50 milliamperes), here’s what happens.

On a good battery I will see a smooth and rapid rise in voltage as each cell in turn begins to charge.
e.g. With a 14.4 volt battery (12 cells of 1.2 volts)
Voltage will rise smoothly and rapidly to 1.2 volts, then to 2.4, passing onto 3.6, etc until finally 14.4 volts is reached and passed – little or no hesitations in the rapid rise of voltage.

On a 'so-so' battery with lazy cells I will see a stepped rise in voltage as each good cell charges.
e.g. With a 14.4 volt battery (12 cells of 1.2 volts)
Voltage may rise but in observable steps to 1.2 volts, hesitate then to 2.4, hesitate then to 3.6, etc. But the final voltage may only reach say 12 volts because 2 cells are not accepting the charge. This can often be cured by raising the charging current to a few amperes for say 30 seconds, discharge the whole battery, then charge again at low current – watching for the elimination or smoothing of the voltage steps and attainment of the full 14.4 volts or better. This process needs to be repeated about three times to rejuvenate the battery. If I still have one cell that remains a problem, then I replace it. However, most times the rejuvenation process works. The whole rejuvenation processes (say 4 partial charge/discharge cycles) takes about 10-15 minutes.

Using this process, I’ve rejuvenated several old Black & Decker stick-type 3-cell nickel-cadmium batteries.
Four times now I ‘saved’ a 3-cell nickel-metal hydride portable phone battery. Why bother? That special sub-AA battery pack for the portable phone costs $44. It would not take a charge from the commercial charger - the lazy cell prevented the final battery voltage from rising above 2.5 volts. Once rejuvinated, the commerical charger would work fine to charge the battery - for another 9 months, then I have to repeat the process.

Rick V

[Stix]

Originally Posted by Boostinjdm

The size you want is "sub-c" in NICAD. Nimh cells work too, but you have to buy the correct Dewalt charger. It's all yellow. I forget the model number. Rebuilding packs is easy if you have the ones that are screwed together. Cells are currently about $2-$3 each so you are looking at $24-$36 in cells for one 14.4 pack. I think the original cells in the Dewalt packs are 1400 or 1700 mAh, but I don't remember for sure. If you buy new ones, look for 2000-2400 cells to give you an increase in run time.

I've been thinking about rebuilding some battery packs with sub-c cells - I found new ones selling for as little as $1.35 on ebay, but from questionable sellers.

From a decent supplier like All-battery.com, 12 sub-c cells will run about $20. Here's a listing on ebay:
12 NiCd SubC 2200mAh Batteries For PowerTools With Tabs Item #290406367795

But I haven't decided to go this route yet - too much to do, too little time!

- Rick
_______________________
Hobart Stickmate LX235AC

[Stix]

Originally Posted by Rick V

I'm preparing to go a new route entirely - see picture 1.
I'm going to replace those ~1.3 amp-hr sub-C nickel-cadmium solder-tab cells entirely.
$3 buys three plastic holders for 4 AA-cells. Three of the 4-AA battery holders fit nicely inside a standard 14.4 battery case. I'm going to use standard AA 2.5 amp-hr nickel metal hydride batteries - that are available just about anywhere.

I like that idea. It's great seeing new ideas and how different people solve problems by thinking outside the box. But I'm wondering about the switch in batteries. Do the AA cells get hot? Weren't they designed for much lower amp output? I've read that sub-c cells were designed for high amp output in power tools.

Also, 12 AA cells at 1.5v = 18 volts - how does that work in a 14.4v tool? Do you use the original 14.4v charger or remove the AA cells for charging in their charger?

Thanks, Rick
_______________________
Hobart Stickmate LX235AC

[Boostinjdm]

Rechargeable cells are normally 1.2 volts.

[Stix]

Originally Posted by Boostinjdm

Rechargeable cells are normally 1.2 volts.

Gotcha - good call. I learn something new every day.

I'm thinking about rebuilding an 18v battery pack like the one pictured in your previous post. But I'm wondering if I should use 15 sub-c cells or the AA cells. Maybe I'll try one of each . . .

- Rick
_______________________
Hobart Stickmate LX235AC

[dugndeep]

I rebuild my own battery packs,not to expensive,I get my batteries from all-battery.com.You can go to their website or go to e-bay,I usually just go to all-batteries e-bay website to get my batteries.Usually just bid and get them for 1 dollar or less a piece.I bought 25 sub-c,always use what they had in them,if they had sub-c use sub-c not AA's.AA just don't have the mah's or the run time as sub-c's.I bought 25 sub-c's to rebuild a craftsman 14.4 drill and a no-name 9.6 volt drill for less than 30 buck's including shipping.I got 25 of their Tenergy 2200 mah nicads,nimah's would be better but cost a little more but they have no memory.These batteries last just as long or longer than the originals.You can get them with tabs or without.I always get them with tabs because you can always take them off or because you usually just need one tab per battery to solder together.........doug