Ni-Cad vs Lithium batteries

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I just purchased online from home depot an edger/trimmer...In the specifications it said electric, nothing mentioned about batteries. and i thought that was what i getting. It turned out it was cordless with 18v ni-cad battery. Now from past experience, i have had bad luck with those batteries...mostly through my ignorance of different type of batteries..Recently i learned that Lithium batteries were the better choice, if i was going for cordless. I went back to the site and sure enough, the heading of the sale did say cordless. Now can someone tell me how to maintain these batteries when not in use? Obviously here in the new england area i won't be using it all year. The manual says nothing about that.
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You've been hosed. Try to return and retrieve your money. NiCd is the worst possible choice for a seasonal tool. Get a Li Ion or corded.
Joe
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Who made the trimmer, HD Ridgid brand has a lifetime warranty on even batteries, but if its maybe B&D dont count on much the second year, with HD I think you have 30 day return, for an edge trimmer I would only use gas or 120v corded. Nicads are considered discharged just when the unit slows, running a battery dead can ruin it, they also need to be charged to their peak then charging must stop or you cook the battery to a shorter life, so you need to know how to determine your charger does it right.
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wrote:

<Who made the trimmer, HD Ridgid brand has a lifetime warranty on even batteries, but if its maybe B&D dont count on much the second year, with HD I think you have 30 day return, for an edge trimmer I would only use gas or 120v corded. Nicads are considered discharged just when the unit slows, running a battery dead can ruin it, they also need to be charged to their peak then charging must stop or you cook the battery to a shorter life, so you need to know how to determine your charger does it right.>
Agree. B&D cordless tools have had the worst performing batteries I've ever run into. The only exception was their cordless lawn mower and those batteries lasted only because I completely disregarded their instructions and did NOT leave it plugged in all the time.
The mower uses lead acid cells, which may be why it lasted, but the trimmers, edgers, drills, vacuums and every other B&D nicad based cordless device I have ever owned did not survive longer than one season.
The drill packs always suffered the same failure mode. The centermost battery in the back failed first because it overheated when charging because it was in the center of a ring of other ni-cads and could not dissipate the heat from charging as well as the outer batteries.
Any tool you buy today should either be NiMH or LiOn. NiCad is old, bad technology, subject to memory issues and premature death. Also, with LiOn cells, manufacturers HAVE to build in overcharging protection. In the B&D devices I took apart, they charged as long as they were kept plugged in and overcharged very easily. There was no autoshutoff when charged circuitry.
LiOn packs will explode if overcharged, so manufacturers put temperature and other sensors in their charging circuits to prevent overcharging. Sometimes, other things go wrong, though:
http://en.wikipedia.org/wiki/Lithium-ion_battery says:
"For example, approximately 10 million Sony batteries used in Dell, Sony, Apple, Lenovo/IBM, Panasonic, Toshiba, Hitachi, Fujitsu and Sharp laptops were recalled in 2006. The batteries were found to be susceptible to internal contamination by metal particles. Under some circumstances, these particles can pierce the separator, causing the cell to short. The cell will begin to rapidly convert all of its energy into heat. This creates an exothermic oxidizing reaction, causing the temperature to a few hundred degrees Celsius in a fraction of a second.[81] A chain reaction occurs when neighboring cells heat up, and in some cases, causes the battery to ignite."
So, not ALL the kinks have been worked out with LiOn batteries, but I'd still prefer them for the power-to-weight ration in any hand powered tool with one exception.
All that said, I often still prefer to use devices that accept standard battery sizes so I can buy and charge my own NiMH cells. Not as convenient as built-in lithium ion batteries, but a certain class of items, like cameras, MP3 players, etc. it's nice to be able to buy batteries when away from a charger or carry ready spares.
-- Bobby G.
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wrote:

IF misused. Otherwise,they are fine."memory issues" has been debunked. you can screw up NiMH just as easily as NiCd,if you don't charge them right.

probably due to cheapo slow chargers,that aren't regulated in any way. Fast charger systems have sensors or smart ICs to monitor charge and shut down when the pack is fully chargerd.

Ok,the guy wanted to know how to maintain the NiCd pack he ALREADY HAS. It's best if you recharge before putting the item away;don't store NiCds if they are depleted. Also,chargers that fast charge (1 hr or less)give better NiCd life. IF you happen to have a slow (trickle) charger,use a timer to charge to the recommended full charge time and no more.it's probably best to remove the pack from the charger when it's finished charging;some chargers will discharge a pack left in it.
One nice thing about Lithiums is that they keep a charge much longer in storage. (but they cost more) both NiCds and NiMH self-discharge in storage. There are a couple of brands of loose NiMH cells that have very low self- discharge,like Kodak,but you don't find them built into packs. They're called "precharged NiMH". I don't know if they are offered in other than AA,AAA sizes yet.
--
Jim Yanik
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That's not true. If your objective is to maximize the life of a Ni-Cad and you are willing to not have a battery in a ready state of use then the below would be the proper way to store the battery.
Run the tool until the battery is drained. With a Ni-Cad that would be when the motor noticeably slows. Store it in this condition if it will not be used for over a month. After long periods of storage the first charge will be of a lower capacity but after a few charges its capacity will become normal.
Things that can harm Ni-Cads are:
Over discharging Over heating Over doing the charge/discharge cycles.
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wrote:

My drawer full of dead NiCad packs takes issues with your statement that "memory issues" have been been debunked. They are just too sensitive to charging issues and UNLIKE LiOn cells, often don't have limiting circuits in their chargers. It's hard to know whether a NiCad tool comes with a limiting charger from reading the box information. LiOn powered tools HAVE to use a limiting charger or they will explode. That's one reason why LiOn is the better choice.
Two more are that they completely surpass NiCad in power delivered per pound of battery, imporant in a hand tool that you carry around, and secondly the individual cells are much less likely to reverse polarity or go completely dead and take other cells down with them. That may be entirely because LiOn chargers detect overvoltage and overheating conditions, but whatever the reason, they are far superior in terms of longevity.
I've had NiCads die (go to 0 volts) and become unchargeable just sitting in a drawer. To be candid, I still have some NiCads bought at Lafayette electronics (a clue to how old they are!) that will still take and hold a charge, but far more of them just died in their sleep. Not the kind of battery the OP wants, IMHO.

Great. How does the OP know which one he's gotten? It's a guessing game, and the final determinant is monitoring the pack while charging or taking the charger apart. Who wants to take the chance you've bought a unit with a charger that has the capacity to kill you batteries if you forget to remove them from the charger promptly.
With LiOn, you can be *almost* certain you're getting the charger you describe. With NiCad, almost the reverse is true because you know the manufacturer of the tool chose a cheaper power source to save money. It's just as likely they chose a cheap charger to lower prices as well.

Are you SURE? That's not what I got from the post. I read that he expected to get a corded unit and got a cordless NiCad instead. I also read that he just bought the unit from HD, and they certainly allow refunds within a reasonable time period. I further read that even the OP knows that LiOn batteries are better.
Taking all those facts into consideration, I am advising him to run, not walk, to HD and take the damn thing back because my experience is that NiCad will not last long, especially with a crappy charger, and that within a year or two, he will face the expense of replacing them, which for some (most?) tools is a factory job costing more than a new tool.

Great advice if someone wants a battery pack they have to shave in the morning. (That's what some soldiers said about our rifles in 'Nam compared to the lowly but much more reliable AK-47 used by our enemy.) If they want a tool that's light and performs rings around NiCad powered ones, LiOn's the only choice, far superior to even the best NiMH cells. I have a lot of power hungry devices that use AA's but for the ones that use 12V's worth of double AA's I've been switching over to LiOn cell packs and chargers because they last twice as long as even the best NiMH but weigh far less.

True, dat. But new NiMH's like the Sanyo Enerloop appear to maintain much of their charge for a year. I haven't personally tested that claim - but I just might to see if it's really true. A year long charge would make them good enough for seasonal work. There's no NiCad battery I know of that will hold a charge for much more than a few months.
NiMH's also don't have to be completely discharged to be recharged. Unless you point me to a reputable site that says the NiCad memory issue is solved and no one sells a memory-effect troubled NiCad, I am sticking with over 25 years of experience and research that says NiCads can't touch LiOn cells for reliability, charge holding, immunity to charging errors and power to weight ratio. Whenever a NiCad pack fails, I replace it with some other technology. Sometimes, like on power drills, I cut apart the old pack and attach a 12V gel cell. Not a convenient as a replacement, but far more reliable and powerful than the NiCad based original.

Anyone with a little ingenuity can deal with that. The 100 LED superbright flashlights I use have holders with two buttons on the end. I made a charger out of some scrap plastic and a 4 NiMH wall-wart charger I got from Allelectronics. I just slide the pack out and into the charging jig. I prefer this system because I can replace problem cells easily. I've been using 2500MAh Maha and Ultralast AA cells in those units, but I am thinking of switching over to the Sanyo Enerloops if they hold a charge as long as they claim.
My theory on flashlights is that they should light up every time you need them. Used to use AA Alkalines, but there's a design flaw in the flashlight that in its normal head down position, you can't tell whether the light is on or off. I say "normal" because this a showerhead flashlight with a huge head studded with 100 white LEDs. It's absolutely unmatched as a light source for microphotography because it's virtually shadowless. I somewhat solve the problem by putting little rubber bumpers on the face to hold the light up a few mm's off the table top. That way enough light leaks out that you can almost always see that you've left it on.

The chemistry for NiMH is slowly improving because each year, new and better batteries appear. Some manufacturers allege that their NiMH double AA cells deliver 3000MAh , but I am skeptical. I'll be able to report more precisely when my new LaCrosse LCD charger arrives that gives a readout on how many milliamps a discharged battery absorbed, among other things.
http://www.thinkgeek.com/gadgets/travelpower/b7fd /
Oddly enough, this multiple featured charger comes with a NiCad reconditioning mode to completely drain and recharge NiCads over multiple cycles. That's a curious thing to add to a battery charger if NiCads don't suffer from memory issues, but both their engineers and I could be wrong and you right.
Just show me the $/URL. (-: It wouldn't be the first time that 25 years of experience goes out the window with some new breathrough, but memory free NiCads I think I would have heard of. Still, to be safe, I'll Topeka it . . . .
http://www.facilitiesnet.com/equipmentrentaltools/article/Building-a-Better-PowerTool-Battery--3001
"The professional grade tools that use NiCad batteries make up a small portion of the cordless power tool market, Fairchild says. "About 15 percent of the market is upper-end tools and about half of those tools that use NiCad batteries don't suffer from memory effect," he says."
So, I still stand by my belief that the batteries you find in specially manufactured items for HD or WallyMart (translation: lowest bid) are not going to be China's best and they are likely to perform badly if subject to the typical (mis)use/charge cycle of a seasonal tool.
There are a lot of things to consider, but if the OP wanted corded originally, I think he should return the unit and get a corded one. Edger trimmers are easier to handle on a long cord than some other tools, like hedge clippers or snow blowers. And a line power trimmer will run for a long time after a NiCad powered unit is only good for one side of a short walkway or less per charge.
-- Bobby G.
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wrote:

Jim is right. There is no significant "memory effect" in NiCds, at least there hasn't been for 30 years or so. There are all sorts of ways to kill NiCds, but the "memory effect" isn't one of them. If you're worried about chargers killing batteries (not anything to do with the mythical "memory effect"), buy only tools that have a quick charger. If you're really squeamish buy only tools with chargers that shut themselves off after charge.

If you allow NiCds to reverse charge, yes, you are asking for trouble. However, LiIons aren't without problems. They're expensive and have a finite life. NiCds are a better choice for many tools. No battery likes to be overheated. LiIon is no better.

Those are probably all salvageable. NiCds tend to grow dendrites, which are repairable (burn 'em out).

What is there about "fast chargers" is difficult to figure out?
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wrote:

then do your homework before buying. The Internet is a powerful tool for researching a potential purchase.

I wonder if Mr.Green knows what "memory effect" actually is. It has to do with charge capacity.

NOT relevant,as the OP already HAS a NiCD tool. At best,a lesson for the NEXT purchase.

Well,Yeah,that's the "self-discharge" thingy...

Except the original poster SAID he HAS an item with NiCD,and also SAID he wanted to know how to maintain them. Sure,he didn't read the package to find out what he was buying,but that's not the NiCD's fault. Sure,he can probably return the item.But that's not "maintaining" them.

Not really "repairable". Sure,you can burn out the dendrites,but the separator still has that puncture in it,and new dendrites will grow.

READ the box? or research BEFORE buying. Or ASK a knowledgeable clerk,if you can find one.

It requires READING and UNDERSTANDING.
--
Jim Yanik
jyanik
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Holy Toledo Tools! It's NOT, as you claim, "at best a lesson for the NEXT purchase." Given the OP's original information, of COURSE he can take the tool back if he has retained his receipt. Based on when he said he bought it, he's certainly eligible for a refund from a place that we both know has a generous refund policy. Based on his originally wanting a corded unit, I think he SHOULD take it back ASAP and get a better tool.
(Especially if he doesn't want to involve himself in a technology like NiCads that have more ways to die than a sequel to "Friday the 13th" or "Saw.")
-- Bobby G.
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I must have missed the announcement when they made it in 1980. The fact that AA hi-end chargers continue to sport NiCad reconditioning modes and my own experience with 100's of AA rechargeables of every make and chemistry out there makes me very dubious of the claim "no significant memory effect."
You're talking about a country of manufacture for these items whose vendors put melamine in pet food, and other various poisons in baby formula, blood thinners, etc. Could you please tell us how you reached your conclusion concerning memory effects?
I think the quality of battery you get in the low end big box tool is still as variable as ever. Keep watching this group for my analysis of batteries from Ebay (from Hong Kong) marked 3000MAh that weigh 1/2 of a normal 2500MAh AA battery and seem to deliver about 1200MAh measured by a meter and not by a vendor's hope of increased profits.
The nice part is that my new LaCrosse charger will be able to work through my remaining inventory of NiCads to investigate AAA and AA memory effects. I retired the loose NiCads because they can't hold a candle to NiMH cells that hold 2700MAh. Since NiCads still come with many items I buy from China, I have a varied lot to test for memory effects. The LaCrosse has reconditioning circuitry for each battery slot, and multiple status readouts pertaining to amount of charge retained per session. It is able to identify any memory effects quite easily.

That's indeed a major part of my issue with NiCads. There are TOO many way to kill a NiCad battery to make it a battery of choice.

Calling the memory effect "mythical" implies there never was one, but elsewhere you state "for the last thirty years" and still elsewhere you hedge your bet even more by saying "no *significant* effects. Which is it?
My personal experience as a photographer through the '70s to the '90s is that NiCads have a memory problem and that NiMH cells, when they arrived, were nearly universally acknowledged to have solved that. I don't know of any photographer that "rolls his own" who uses NiCads anymore. It's either NiMH (for those who prefer loose AA cells) or LiIon for those who prefer the highest power-to-weight ratio available.
Even if I were to agree that "memory effect" is a Big Lie, poorly designed NiCad battery packs that have center and tower cells in their battery clusters are doomed to failure because the cells in the center can't dissipate heat as effectively as the outer cells and fairly quickly bring the whole pack down. I have at least 6 B&D drill packs that died this way and they all had self-regulating quick chargers. It's such a known problem with the Firestorm series of drill packs that some guy on Ebay is making a living off it:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item20510366631

Thanks for showing that the quest for a NiCad powered tool seems to have all sorts traps and dead ends, far too many to make it the battery to choose when you have a choice.

ALLOW? That conjures up a fascinating image of my charger contacting my cell phone to deliver a canned audio message: "Bobby, a cell in your pack is about to reverse polarity. Do you want me to allow this travesty? Bobby??"
My point, as continually well-illustrated by your examples, is still the same. There are far too many ways to kill a NiCad battery pack, and the cheaper the tool, the more ways there are. A guy wanting a power trimmer shouldn't have to become a rechargeable battery autodidact.
Let me ask you: When was the last time you saw a NiCad powered smart phone, camera or laptop? A long, long time ago. They are just not good enough. Worse, still, buying a $40 NiCad tool instead of a $60 LiIon *looks* like a good bargain - until you have to figure in the cost of a replacement pack because the NiCad one is almost certain to die a much younger death. It's false economy in a number of serious dimensions.

And NiCads have an infinite life? Of COURSE batteries have a finite life.

Name what tool and say why. They are NEVER a better choice on anything but price and that's often not even true in the long run.

You're ignoring what I said. LiIon *IS* by definition MUCH better. Why? Read what I said. When you buy a LiIon, tool, you're *certain* that you are getting a charger that checks for overheating. You have no such guarantee with a NiCad powered tool. Maybe there's a heat cut off, maybe there's not.
You could be getting one of many types of NiCad chargers, too: Trickle with no overcharge protection, fast/trickle with no overcharge protection, fast only with no trickle with no overcharge protection and all of the above WITH overcharge protection. That's a LOT for anyone not intimately involved with battery technology to consider.
Choosing LiIon cuts through all that crap of vetting your charger by insuring you're getting a charger with both overcharge AND overheat protection. That's because the battery chemistry DEMANDS it. You just can't mistreat LiIons the way you can NiCads because the chargers HAVE to be better.

C'mon, get with reality. Who but battery freaks are going to go around zapping dendritic whiskers out of drill battery packs? It assumes you've
a) taken the pack apart (often made extremely difficult by the manufacturers),
b) found and disconnected the bad cell,
c) found a high amp/low voltage power source and
d) maybe have a spare blast chamber lying around to contain the possible explosion. Is that realistic advice for the average Joe Homeowner?
My sense of this newsgroups is that we're *mostly* trying to give real world advice to someone whom I don't believe, based on what he wrote, is going to cracking packs and zapping whiskered batteries.
In fact, I think that description includes *most* people in the world. The fact the NiCad cells so routinely suffer this whisker problem is just another reason to steer clear of them. There is no such issue with LiIon cells. Who wants a battery that needs its whiskers shaved?

Consider this. The OP thought he was getting a *corded* tool. Does that tell you something about what the average consumer finds difficult to figure out? If it doesn't, it should. You can't *really* be sure of what you are getting unless you take the charger apart or monitor the whole charging process with a voltmeter. The B&D Firestorm drills come with a fast charger that then trickles. Leave it in too long, and it's ruined. So selecting just a fast charger is not enough. Those kinds of issues do NOT occur with LiIon because the charging process demands strict monitoring and current limitation.
I'm making it easy for people who aren't battery charging experts:
o LiIon packs ALL have built-in over-heat and over-charge protection by design.
o They are lighter per amp of output by more than half, giving LiIon tools MUCH more power per charge. Often it's the difference between doing the job in one run, or having to wait around for a recharge.
o Fewer LiIon cells are needed per pack to reach an equivalent voltage in NiCads, reducing the odds of a single cell failure.
o Perhaps most importantly, you can leave a LiIon powered tool sitting for months and it will still have a charge. You'll need to charge a NiCad unit far, far more often. Not being ready to rock and roll at the moment you need it is a bad trait in a power tool.
Whether or not the memory issue has truly been resolved for all NiCads is almost meaningless in the context of NiCads myriad other weaknesses. It's a poor choice for hand held tools of the Big Box variety. Yes, you can spend more and get higher quality NiCad packs and chargers, but even then, you'd be carrying more weight for less power, a bad trade-off in a handheld power tool.
There's a reason nearly every cellphone, netbook and laptop is now powered by LiIon and not Nicad. NiCads are poor performing old technology with too many liabilities and too little power per ounce of weight.
Eventually NiCads will disappear - it's happening as we watch. That's probably a good thing, because ecologically speaking, they are also the worst of the three (LiIon, NiCad and NiMH).
-- Bobby G.
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I know my Ryobi chargers overheat batteries, my Makita and Ridgid dont. I have 20 yr old Makita Nicad packs that work, my Ryobi charger and cheap batteries dont last. LiIon by design dont last more than 4-5 years. You get maximum life with tools by not over discharging, over charging, and most important not overheating a pack. HDs ridgid ofers lifetime battery warranty so thts what im buying and my Ridgid Nicads are fine after 4 years. A nicad pack if fully charged just when voltage peaks and starts to decline, that is when the battery starts to convert energy to mechanical energy and cooks the cells. Having a good charger, knowing what its doing in terms of voltage cutoff and how how far you discharge it and heat it determine a good batteries life, but the cheap chinese batteries may not last any way. Sanyos - Panasonic are best and in the best tools
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wrote:

Are you an engineer who has designed charging circuits. Yes, you likely did miss something. Have you ever heard of "marketing"? That one word, and the myth of "memory effect" is enough to flood the market with all sorts of garbage.

Don't be an ass (I know it must be difficult).

They buy their batteries from the same companies as the high-end products. Yes, there may be a quality difference (even a real capacity difference) but the chemistry is well known.

You can investigate anything you want, but you won't find a "memory effect" in recent NiCds.

*ANY* battery is susceptible to damage. Easily. That's the nature of the beast. NiCds may be less tolerant of some sorts of damage than others, but the key word here is "less". All will be damaged by neglect. Don't do that.

The very first NiCds had a problem that was called "memory effect". Those problems were fixed but the term stuck to every failed rechargeable battery since.

Your experience means nothing. I'm sure you had battery failures, but they were *NOT* the fabled "memory effect".

TWEET! "Time out to move the goal posts."

Wrong. The above applies to many battery technologies. NiCds don't like to float charge and shouldn't be used in an application that requires float charging. SLACs are a better choice for things like flashlights and alarm systems. NiCDs are much better in other applications. Did I ever say that NiCds were the best solution for all applications? No, you're lying.

Wow, you're tense. Hint: cells may reverse charge if the multi-cell battery is allowed to discharge too far. Yes, *allowed* is the right word.

All batteries are susceptible to damage from improper use. "Improper use" is somewhat technology dependant but there is no technology that is immune to abuse. Don't do that.

Your point? When was the last time you saw a LiIon powered UPS? Emergency lighting system?

NiCds aren't limited like Li-Ion, no. Li-Ion has a definite number of charge cycles. After that it's capacity goes down rapidly. I'm sure you've never heard of a cell phone being toast after 18 months.

Cordless drills, saws, and anything that has a very high current draw. NiCds have a very low series resistance. They're a bit bulkier, so aren't favored for compact tools. NMH was supposed to replace the NiCd, but it had its own set of issues.

You're *wrong*. Yes, you may have to read a bit to get a tool with a decent charger, but perhaps that's too much to expect from you. If you buy a cheap tool with LiIon cells, how are you going to *guarantee* a smart charger? It's not a fundamental given that they'll treat the batteries any better than cheap tools do with NiCd.

You could read, too. Maybe not.

Complete nonsense.

Maybe. Single cell batteries are already apart. Multi-cell NiCds can often be recovered, as well. I've done it, though I generally don't bother.

Ok, my sense is that respondents here are mostly talking through their hat, as you've demonstrated.

There are a *ton* of issues with Li-Ions, all of which you've conveniently skirted in your disdain for NiCds.

Bullshit. It tells me that the OP didn't read anything about what he was purchasing. That's the bottom line. It also tells me that you haven't a clue.

Show me where this is a law. It's *not* a requirement of the technology. I can't wait until you get burned (NPI) and come back here whining.

They don't produce as much current as a NiCd. Asking them to will damage them.

Cell phones are about the easiest on batteries of any imaginable application. Yes, there is a reason Li-Ion us used for such applications and NOT for UPSs, and such.

They'll disappear only if the government demands it. In those applications they'll likely be replaced with NMH, not Li-Ion.
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Li Ion is great , but do they last more than 4-5 years. I have all Nicad and some 20 years old that still work a bit. LiIon I dont believe from what I have read have the longevity.
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wrote: <stuff snipped>
<Li Ion is great , but do they last more than 4-5 years. I have all Nicad and some 20 years old that still work a bit. LiIon I dont believe from what I have read have the longevity.>
In my view, longevity at half power is mostly worthless. Who hasn't had a drill or some other tool conk out prematurely because of bad batteries only to find that the replacement batteries cost more than the original tool and TWO sets of batteries!!?
I have one set of tools, Skil Flexicharge power screwdrivers, that run on 3 easy to access and replace NiCad cells. In fairly regular use, I have to dispose of the 3 cell packs after three years.
If the timer I use to limit overcharging fails, (or I fail to set it correctly) they die much more quickly. Since I have 5 of them, all taking the same chargers and holders, they were worth keeping running, even with NiCads. But the units came with a wall holder/charger that would quickly ruin the batteries if you didn't unplug the unit at the wall. It was designed to fail, endlessly trickle charging a NiCad battery. The suggestion was clear, that you keep it plugged in all the time and buy new packs every sixth months or so, because treated that way, they packs seldom lasted longer.
Since the replacement packs cost $12, I don't even rebuild them anymore. It's not worth the time. But I do keep the good cells because it's usually only one cell in a pack that fails and as you point out, they may still be useful when I can no longer acquire new packs from Skil and have no choice but to roll my own.
My IRobot Roomba Dirt Dog charging base is the same way. Leave it plugged in an ready all the time, and eventually cells only hold enough charge to clean for 5 minutes instead of an hour, even though the charge light showed green. I have one pack that's completely ruined as a result of just being on standby charge for less than a year.
-- Bobby G.
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wrote:

Often. I have a couple of Dewalt drills that I bought because the batteries were cheaper than the drill + charger + batteries. I didn't need the drill, but why not when it was free? BTW, most batteries can be rebuilt easily, at a reasonable cost.
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I have a model 2207 3.6v SKIL Twist Cordless Screw Driver with a battery pack that won't run the driver. Charging only makes the pack feel warm. No load voltage measures 4.034 volts. Souinds like you folks have succeeded in opening the SKIL battery pack to replace the three NiCd cells and reuse the battery pack? Replacement cost for battery is $25 including shipping. I have tried but cannot see how to open the pack.
I sure could use some suggestions.
Did I read correctly that you attach external wires to the SKIL driver and run the driver from an external battery pack which does not slide into the housing?
Many thanks, Dave_s
Robert Green wrote:

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These are 3.6V units and can leave the charger as hot as 4.3V. Your voltage sounds as though the pack is still good.
This model of screwdriver is infamous for its bad battery contacts deep within the guts of the screwdriver (I own many which is why I know).
Look down the insides of the unit with the pack out and try to see whether the two spring terminals are clear of corrosion. I'll bet there's plenty. I often have enough crud on the contacts to make a brand new pack appear bad. They are very hard to clean (I use a Dremel grinding head mounted on the end of a dowel and do it manually) but they *are* cleanable, eventually. If the collet lock is off, and the battery reads over 4VDC, then you *should* have some sort of reaction from the drill. Since that doesn't seem to be your case, I'd vote strongly for the corroded contacts as the first place to look.
You could take the unit apart to clean the contacts, but there's an enormous number of gears, rings, plates, etc. that tend to fall out and become very difficult to reassemble. I would try very hard to clean it without taking it apart.
I've even taken to gluing small strips of sandpaper on a dead pack, right on top of the battery contacts. Inserting the "sandpaper enhanced" pack and removing in a few dozen times often cleans the contacts enough to put you back in business.
If you are convinced it's the battery, you twist off the cap with the red "ears" - it's like a bayonnet lock, and the batteries slide out very nicely. It's one of the easiest packs I've run across for rebuilding, although at $12 a pack from Ebay, I have little incentive to "roll my own" anymore.
The Skil 2207 is a great screwdriver - fits well in the hand, has a single pushbutton for forward and reverse, a collet lock and enough power to do the job without shredding the screwhead. I've bought a lot of other power screwdrivers, but none has measured up to the Skil.
-- Bobby G.
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Bobby G.,
    I sure will try each and every thing you suggested!!!!! Interesting that the battery pack is still possibly usable. Many thanks. Dave_s
Robert Green wrote:

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You're welcome. I hope it works out for you. They are nice little units with that one fatal flaw - hard to reach battery contacts that get corroded. Many good ones end up on Ebay "as-is" that just need a little cleaning.
There are three little 1/2 sized "C" type rechargeable NiCads in a row inside the pack with a nominal voltage of 1.2V. You can often tell how many cells are dead because bad packs typically register either 1.2V or 2.4V depending one whether one or two cells have died. I just tested a brand new pack after a 12 hour charge and it reads 4.26 volts so I assume it's the contacts in your case.
If you haven't used or charged the battery much and you haven't left it in a charging holder for days on end, I'm more than 90% certain it's the damnable contacts. It might have cost Skil more, but the contacts for a rechargeable battery (a known failure point) should be accessible. With two bits of wire, Skil's designers could have easily moved them to the back end of the unit, where you could clean them with a Q-tip. Instead, they are at the end of a long, narrow tube, where reaching them is a nightmare.
NiCads can give off mildly corrosive fumes as they heat up, charge and discharge. The metal Skill chose for the battery contacts seems to born to corrode, especially if the unit, a nice heat-absorbing black, is left out in the sun and heats up enough to make the batteries outgas. The center contact is usually pretty easy to see with a flashlight - if it's bad, it's bright green. The side contact takes a bit of searching - but you can see it clearly with a long dental mirror.
Charging a bad pack with a zero-volt cell in it will melt down the charger. I've melted a few, and finally got a twelve hour spring-powered timer to plug it into to make sure it turns off after a 12 hour soak.
I also drain them (a big spring clip to keep the button clamped) if I have to recharge them before the charge dissipates over time . . . just in case they have a memory effect. Now, in light of recent discussions, I am going to mark one of the three new packs as "don't discharge before charging" so I can personally investigate whether the NiCad memory effect is fact or had been made fiction by improvements to the chemistry.
If it somehow turns out to still be a bad battery (you would have to put a test load on the pack to be sure it's still good and that's not easy given the contact design - it's alligator-clip proof!) you could try this guy:
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item60173612655
He's got an extensive tutorial on that page and offers to buy used Skill powerdrivers from people who want to upgrade and not buy a new pack or charger. I'd buy more if they still made the screwdriver because even with the terminal corrosion issue, it's one of the best designed powerdrivers out there.
The Ebay guy's packs have lasted for at least three years of heavy use and some misuse. No telling how long this new batch will last with a new timer charger that can't overcharge them. I suspect the motors will die by then.
If you do get it running again, be careful not to leave the pack on the charger for more than 16 hours or it will die a premature death - of that you can be sure.
Good luck and let us know what happens!
-- Bobby G.
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