Ni-Cad vs Lithium batteries

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.

Reply to
krw
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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.

Reply to
krw

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:

Reply to
Dave_s

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.

Reply to
Robert Green

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.

Reply to
Robert Green

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:

Reply to
Dave_s

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:

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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.

Reply to
Robert Green

If you can give me an estimate of the current drawn by screw driver, I can measure the battery voltage while drawing that current.

Does the screw driver draw approximately 1/2, 1 or 2 AMPS while driving a screw (under load)? I can how much the 4.0 volts drops under load.

Thanks, Dave_s

Reply to
Dave_s

If you can give me an estimate of the current drawn by screw driver, I can measure the battery voltage while drawing that current.

Does the screw driver draw approximately 1/2, 1 or 2 AMPS while driving a screw (under load)? I can measure how much the 4.0 volts drops under load.

Thanks, Dave_s

Reply to
Dave_s

Bobby G. repair info has resulted in a Successful repair!!!!! After removing corrosion from internal contacts, the SKIL Driver now runs again. As Bobby predicted, the Battery Pack was still charged and OK.

Many Thanks, Dave_s

Dave_s wrote:

Reply to
Dave_s

Unfortunately, I can't answer that question for you other than to say the batteries, when new, can power the motor continuously for at least two hours. It's just too hard to clip the motor and battery contacts in such a way that you can take a current reading.

I don't know whether this helps, but you can get the motor to run (slowly) even though one of the three cells is dead.

Put a bit inside the tip and twist it around a few times with a pair of vise-grips to make sure the red sliding collet lock isn't engaged and to break any "stiction" that has occurred from a long period of non-use.

My money's still on corroded contacts if the battery hasn't been left on charge for too long.

-- Bobby G.

Reply to
Robert Green

All Right! Thanks for the report. Just make sure you don't overcharge that sucker because that WILL kill it for sure. We may not have solved the problem of the OP and his edger, but at least something good came out of this thread. Although I have not tried it yet, a friend suggested I coat the contacts with a thin film of vaseline next time I clean them to keep them from re-corroding. You'll probably have to reclean them in a year or so. )-: But at least you saved $ by not replacing a perfectly good pack.

Happy screwing! (I couldn't resist!)

-- Bobby G.

Reply to
Robert Green

I have done that with the B&D Firestorm drill power packs, not the Skil. The drill is designed so that cutting the pack open and removing the batteries gives you a good platform to attach a 12V gel cell and doesn't change the balance of the drill much.

I suppose you could do the same with the Skil powerdriver, but it would make it pretty awkward to use.

I rebuilt the NiCad pack *once* only to discover that the center battery kept failing because it would overheat during charging. Instead of wasting my time rebuilding it again, I cut away the batteries, saved the good ones and attached the 12V gel cell to the remaining bottom plate of the old NiCad pack. Cost a lot less than buying a new pack (about 25% of the cost of a new pack) and have lasted way longer. I first used Velcro to attach the battery to the battery pack plate until one fell off and hit my foot. Now I strap them to the platform with large hose clamps. (-:

The design of the Firestorm battery pack (and many other drill packs that bury a cell inside ring of cells) is faulty so there was no point in continuing to try to rebuild packs that would only last through a few chargings. The drills come with fast chargers that really heat up the pack. I suspect a slow charger wouldn't kill the center cell as quickly because it would be able to shed charging heat a little better.

It's a great way to use up what's left of a UPS battery that's not really dead, but "rejected" by the UPS for being slightly too low in voltage. The Firestorms run on 9.6V but have a variable power trigger so you can run them from 12V without motor damage if you don't bear down all the way on the trigger switch.

-- Bobby G.

Reply to
Robert Green

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