Drill Battery Pack Dies Suddenly!

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WildBoar
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Drill Battery Pack Dies Suddenly!

Post by WildBoar » Sat May 03, 2003 1:29 pm

Over the past few years I've purchased
several professional grade battery powered
tools. I drove seven or eight thousand
screws with a Porter-Cable drill before
the battery packs gave out.<p>I now have an 18 volt Milwaukee drill that's
about 17 months old. Unlike the Porter-Cable
unit, this Milwaukee drill has been used
about once a month for light duty projects.
One of the two battery packs that came with
the drill is dead. (18 volt NiCd, 2.4 amp hours,
catalog number 48-11-2230.)<p>I measured the no load voltage on the remaining
good pack. Its 20.62 vdc at full charge. The
dead pack reads 11.76 vdc. I tried completely
discharging the pack using a low value, high
wattage resistor but it didn't make any
difference. It still reads 11.76 vdc.<p>A new pack costs $60.00. My first thought was
to have the pack rebuilt by a company like
Primecell which has advertised for years in
Nuts and Volts. The problem is they want $44.50
to rebuilt this 18 volt pack. The pack weighs
around four pounds. It would probably cost
ten to fifteen dollars shipping round trip!<p>I thought about rebuilding the pack myself until
I opened the pack and saw that large stack of
individual cells. Even If I could find the
replacement cells I don't think I could ever
get them back into the case!<p>Has anyone successfully rebuilt one of these
packs? If you have, where did you buy the
cells? <p>The final question is: How much money did you
save, and was it worth all the time and trouble? <p>WildBoar<p>[ May 03, 2003: Message edited by: WildBoar ]</p>

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Edd
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Re: Drill Battery Pack Dies Suddenly!

Post by Edd » Sat May 03, 2003 2:03 pm

mmmm….Milwaukee….that’s the same drill I have. The 18 V version and 2 of the 12v models. The newer one has given no trouble but I’ve rebuilt the 12v versions at least twice. I admit that the batteries are in a weird tandem mechanical configuration at the top but it is no problem if the tab style of replacement of batt is used. On the one time I used the standard conventional button top cells and had to trim off the bottom of the batt casing with a Dremel with cutoff wheel and fab a 1/2in extension to the housing with Bondo, now it will accommodate either. In my case I used surplus ni-hydride from a H/D laptop computers battery pack. Also at one time I got two freebies of the whole Milwaukee batt pack assemblies from Homeless Depot as they usually ( dump ?) or send in for proper haz disposal, units that a customer may have left at the time of buying a new packs….and that’s the case I ran into . In the end I now have 2 running packs and 2 spares on standby on a homebrew bench supply C/C charger.<p>Addenda: On the 18 v charger unit, I do seem to see that it tends to cook the cells a bit if left in the unit for an extended period of time....I much prefer a gentler charge period/time. <p>73's de Edd
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;)<p>[ May 03, 2003: Message edited by: Edd Whatley ]</p>

Dean Huster
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Re: Drill Battery Pack Dies Suddenly!

Post by Dean Huster » Sat May 03, 2003 3:41 pm

I'm considering upgrading now that I'm professionally in the construction business. But then I have to weigh out the advantages and disadvantages of cordless drills (and cordless tools in general) and make a prudent decision. I've decided that you have to really like or have a special and frequent need for the cordless drills to justify the expense of purchase, hassles of charging and expense of battery maintenance.<p>My first thoughts into this occured six years ago when I helped to demolish a large set for a Christmas program at church. I'm talking about enough 2x4, 2x6 and 2x8 framing on the stage to build a decent-sized shed. There were four of us, three with various brands of cordless drills including Milwaukee and DeWalt and me with my Craftsman 120v drill and 100-foot extension cord. The other guys were constantly recharging batteries and having lots of down time as all of there batteries were either dead or charging while I was still pulling the toughest screws non-stop.<p>That was the first of many applications that pointed me to the fact that I'd be much better off with a good 120v drill and a couple of hundred feet of extension cord and a lighter-duty cordless drill for those jobs where I just couldn't get a cord -- and those jobs don't occur very often.<p>The 120v drill has higher RPM and a heckuva lot more torque; available in larger sizes; a lot less expensive to purchase, even if I buy a couple of them; virtually no maintenance costs; virtually no down-time; and just the hassle of having to be plugged into 120v all the time, but I'm usually having to have several of those tools anyway: table saw, miter saw, belt sander, router, etc.<p>I realize that this post isn't helping out the problem begun on this thread, but it might be a heads-up to folks who are lured by the technology and "convenience" of a cordless product. Like "cordless" cars, there's still a lot of improvement needed before they outdo their corded counterparts.<p>Dean
Dean Huster, Electronics Curmudgeon
Contributing Editor emeritus, "Q & A", of the former "Poptronics" magazine (formerly "Popular Electronics" and "Electronics Now" magazines).

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skrallman
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Re: Drill Battery Pack Dies Suddenly!

Post by skrallman » Sat May 03, 2003 5:22 pm

WildBoar,
I've had a few battery packs made, and made a few myself from surplus battery packs. You might save a little if you DIY, but typically they pack those batteries in there pretty tight which makes it a big hassle to get it all back in.

I think it really comes down to how much you like to tinker around. I don't think you'll save a significant amount of money. 2.4Ahr sub-c's (assuming they're sub-c's) are about $4-$5 each. Sounds like you may have a couple of reversed cells. So, that would be about $10, plus shipping, plus $20 to $30 worth of hassle factor.<p>Check your yellow pages for battery suppliers. I've found several local shops even in my smallish town that have flat top nicd's and nimh's and will make up packs. Also, there are lots of battery suppliers on the internet. Here's one I've used. They'll put tabs on the flat tops for you and they'll build packs too.<p>Another thing to consider is the batteries in a pack are usually matched for capacity. If the cells are not matched some will go dead before the others. When that happens the others begin to charge it and it's polarity can become reversed and the pack will never charge back up to full voltage. You won't have any control
over that is you splice in a couple of cells, but you'd probably have no troubles as long as you don't over discharge the pack. Something you shouldn't do anyway.
Good Luck.
Scott

WildBoar
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Re: Drill Battery Pack Dies Suddenly!

Post by WildBoar » Sun May 04, 2003 8:18 am

Thank you Edd, Dean, and scottK.<p>I really appreciate your replies to my
posting.<p>I made one mistake when I quoted the price
of a new pack for this Milwaukee drill. The
current price is now $80.00 not $60.00!
That $60.00 price was seventeen or eighteen
months ago when I first bought this drill
kit.<p>I paid $210.00 plus tax for the entire kit.
$44.50 plus shipping that Primecell is
charging doesn't seem so high anymore, since
a new pack is almost double that price.<p>I've had very good luck with professional
grade battery powered tools, until now,
that is!<p>Thanks for all your help and advice.<p>WildBoar

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MrAl
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Re: Drill Battery Pack Dies Suddenly!

Post by MrAl » Mon May 05, 2003 5:27 am

Hello there,<p>I've rebuilt a few battery packs in various
types of tools and havent had any problems.
Usually i find one cell goes bad first, so
if you replace that one cell you get another
6 months out of the tool, then you have to
replace another cell etc.
You can usually figure out which cell is bad
by letting the tool sit overnight, then check
each battery with a volt meter. The lowest
battery is the bad one. If you connect the
charger up while measuring the individual
battery voltages, you will usually see either
one of two conditions:
1. one cell is low and stays low, while the
other cells voltages begin to climb up over time.
2. one cell is low and climbs up much faster
then the other cells voltage, and reaches 1.4v
fairly soon.<p>Either of these conditions probably means that
cell is bad. You can then remove that cell
and check more carefully by fully charging, then
discharging and timing the discharge time
with a known load current.<p>Of course if you find a reversed cell voltage
that cell is most likely bad too.<p>I have also found that the packs go bad too
soon if they are left on charge for long periods
of time. One year is typical.
The best bet is to charge for maybe 24 hours and
then unplug, unless your charger is a fast
type. You'll have to check the charge current
with a current meter to find out for sure.
Once you know the chargers current, you can then
figure out the max charge time by taking the
ampere hour capacitor of a cell and multiplying
by 1.4 to make up for the charge/discharge cycle
inefficiency. Divide that by the current and you
get the time to fully charge.<p>I have an older drill i plan on upgrading soon
too. It only takes 3 cells and i plan to use
it as a second drill for drilling a pilot hole.
I found some cells on the web for $2 each so
it's only going to cost $6 plus UPS shipping.<p>BTW, drilling a pilot hole first means putting
the screw in takes less energy which runs the
battery pack down less per screw, but it does
take more time to do.<p>Good luck with your circuits,
Al
LEDs vs Bulbs, LEDs are winning.

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