Ni-Cad Batteries

[bborr01]

Gentlemen,

I would like to share some information about Ni-Cad Batteries.

I doubt that it is a secret to most of the people on this site that Ni-Cad batteries have a memory, but wonder how many get the most out of their batteries.

Case in point: I recently bought one of those attachments that goes in a 1/2 inch drill to raise and lower the knee on my vertical mills. (Best $35 I have spent in a while). It uses some pretty good torque to lift the knee so the maker recommends using a corded drill.

I also have a bunch of DeWalt 18 volt tools and XRP batteries, some of which are nearly 10 years old. While the old batteries are not up to new standards, they are probably about 70 or 80 percent of new level.

One of my brothers bought the same kit that I have a couple of years after I bought mine and he is on his third set of batteries. When he needs the drill, he charges the batteries without discharging them first. Bad mistake.

What I do is when my batteries get too low to be useful for the task at hand, I put them in my vacuum and let them run down until the vac is hardly turning. Before I bought the vacuum, I used the flashlight to run them down. It took longer, but it worked fine. One other thing. I always let them cool down before charging them and again after charging them before use.

Hope this helps save my fellow HSM'ists some $$$$$$ on Ni-Cads.:)

Brian

[The Artful Bodger]

Aside from the question of the different types of rechargable batteries I think it is important to understand the difference between a 'battery' and a 'cell'.

A cell is a single unit such as a 'C' cell whereas a battery is a number of these connected in series.

If a battery is discharged to zero one of the cells will reach zero first and from that point on is being effectively 'reverse charged' which will destroy the cell and once that cell is destroyed the entire battry is useless.

[Black_Moons]

bborr01 is very correct on that you must fully discharge nicads aprox once a month, Reguardless if your using them or not for best life. 'babying' them is not good for them, they thrive on 'abuse'.

Its not the so-called 'memory effect' as that does not affect modren cells or even consumer cells period, But crystal growth that results when you charge the cell, this growth is reversed by discharge, with deep discharge being the most effect at reverseing it. Once the crystals puncture the seperator of the cell the battery will self discharge quickly and may even appear as a near short depending on crystal size. (Shorted nicads have been known to be revived by giving them a controled surge of current, but its not something you want to have to do)

[Allan Waterfall]

I thought NiCad batteries were being phased out now.

Allan

[Black_Moons]

I thought NiCad batteries were being phased out now.
Allan

Oh, they have long since been made illegal for consumer use!...
Except for power tools, Medical applications, industral applications and anyone else who ever wanted to actualy use nicads over nimh or any other battery type. :rolleyes:

[bborr01]

I have had some of these same batteries sit for many months at a time and go so dead that the drill would not even make a noise. Put them in the charger and FULLY cycle them a couple of times and they work pretty good. As I said, some of these batteries are nearly ten years old.

I have 5 of these xrp batteries in 3 different kits. Some kits like the right angle drill don't get used very often and the batteries just sit. Now I have put them in a row and intend to rotate them so they all get used regularly.

Brian

[Bob Fisher]

I have a 9.2 V Makita drill that is at least 12 yrs old. Both batteries still hold a charge. I have since scrapped a 12V Dewalt, cause the batteries would not hold a charge. I treated them the Same and have no idea what accounts for the difference in longevity. On another note, I had a 18 V Milwaukee batteries rebuilt for about$40 each. Performance is better than new. Go figure! Bob.

[Boostinjdm]

Now I have put them in a row and intend to rotate them so they all get used regularly.

Brian

I numbered mine and always use them in order. When they won't turn the screw or drill the hole, they go on the charger and they stay there until needed I get years of heavy use out of them. I have 3 batteries right now and depending on what I'm doing, all 3 of them could go through multiple charge cycles in one day.
I don't even own a corded drill.

[Black_Moons]

I numbered mine and always use them in order. When they won't turn the screw or drill the hole, they go on the charger and they stay there until needed I get years of heavy use out of them. I have 3 batteries right now and depending on what I'm doing, all 3 of them could go through multiple charge cycles in one day.
I don't even own a corded drill.

Ah, Don't leave em in the charger, That trickle charges em and thats bad. With slow chargers it can be downright fatal to a battery, though some modren fast chargers properly shut off.

[J Tiers]

Go pay attention to what TA Bodger said.....

AS SOON AS the speed starts to slow on whatever the tool is, swap to a charged battery and continue, while charging the "low" one you took out.

"Fully" discharged is discharged to the point the voltage reaches a "knee" and starts to drop fast. As TAB said, if you try to get the last bit of use, you almost certainly reverse charge at least one cell, and that kills it fast.

Don't worry about "memory".... "memory " won't kill a battery as fast as reverse charging does, and you can always drain it to the "stop using this" point, and let it self discharge from there, if you want.

[Boostinjdm]

Ah, Don't leave em in the charger, That trickle charges em and thats bad. With slow chargers it can be downright fatal to a battery, though some modren fast chargers properly shut off.

Tell that to my batteries that have been abused for years and keep on ticking.
My chargers have some fancy cycle that kicks in after 8 hrs and is supposed to "tune up" the batteries.

[Bill736]

Some NiCad chargers first discharge the battery, and then charge it. I assume that type is for single cell batteries only. One thing that does puzzle me, however, is a warning on one of my Sears NiCad cordless drill battery pack chargers. The warning is that there are high voltage contacts down in the charger well, and not just the low voltage contacts I would expect. What gives there ? Is that because it's a fast charger ( one hour), and they're using an elevated voltage to charge the 19.2 volt battery pack ? Or is part of the charger circuit inside the battery pack ? I've taken a few of those battery packs apart, and never seen any circuit elements besides the battery cells themselves.

[psomero]

Bill, they have multiple cells in series to get a nominal voltage in that range.

if you divide the pack voltage by the number of cells in series you'll get the nom. cell voltage (or vice versa for nom. cell voltage to number of cells in series).

you probably saw the cells connected + to -, right?

[darryl]

There's no high voltage there, that's just a warning to afford the company a bit more freedom from lawsuits.

You might be able to measure something like 30 volts or so, depending on a lot of factors. I suppose that could be described as 'high voltage'. It certainly would be if you look at in terms of flashlights and kids toys.

Talking about nicads, I'm starting to see battery packs rated much lower than the typical 1.3 AH which was the standard for decades. It went up from there to the point that you could buy a 1.7AH pack- now I'm seeing 1.0 AH, and the other day I saw a cordless drill with a .8AH battery. Standard size drill and battery pack, but they must really be cheaping out on the battery chemicals.

What's the best way to enhance the life of a nicad pack when you know it's not going to be used for weeks or months? (or years)

[Black_Moons]

What's the best way to enhance the life of a nicad pack when you know it's not going to be used for weeks or months? (or years)

Discharge it once a month anyway, then recharge it.
Perodicly consider discharging it with a very light load that will run when nothing else will untill thats also dead. (Also good to improve capacity of older, tired battery packs)

[J Tiers]

There's no high voltage there, that's just a warning to afford the company a bit more freedom from lawsuits.



ABSOLUTELY NOT TRUE, AND DANGEROUS

There is 120VAC down there....

The reason is that many of those chargers do not use a transformer or any form of isolation. The contacts are protected, but they are what UL calls "conductively connected to the mains voltage", i.e. not in any way isolated.

The BATTERY will only see the correct charge current, because it is connected BETWEEN the internal contacts.

The issue for you is that if you touch one or both contacts AND some OTHER grounded object at the same time, you will get a shock.

[darryl]

Yeah, I thought about that- then I figured they wouldn't be allowed to manufacture something like that. You could so easily get a finger in there, and a warning wouldn't be enough. I have never seen a charger where the secondary wasn't isolated from the primary voltage by some means. Those must be the cheapest garbage going-

But if that's the case, JT is right and my comment was stupid and should be withdrawn.

Anybody who manufactures a charger that way should be sued before someone gets killed.

[J Tiers]

Anybody who manufactures a charger that way should be sued before someone gets killed.

Not hardly......

The contacts are covered by the case, and only the battery terminals can touch them.

AND, if you have ever owned a reasonably recent DeWalt, B&D, etc charger, you most definitely DID have a "charger made that way".

They are just as safe as ANY OTHER MAINS CONNECTED APPLIANCE.

You trust your life to a "flimsy plastic case" when you pick up a corded drill, etc. You owe your life to the "thin plastic insulation" and skinny ground wire inside of a chop saw, or lathe when you trustingly lay hold of the CONDUCTIVE METAL case of that device.

There is NO REASON why you should somehow believe that a battery charger, which is properly guarded and meets the correct IP accessibility requirements is any less safe than the hand-held food mixer you or your wife or your children use in the kitchen.

[wb2vsj]

Here is DeWalt's official view on their batteries and chargers (See page 2)

http://support.dewalt.com/ci/fattach/get/48728/

IMO It's going to boil down to how you use your tools as to how long the battery packs are going to survive.

My experience has been the same as Boostinjdm's. That may not hold true for others.

Walt

[darryl]

'properly guarded' etc- sure if that's the case, then it's as safe as any other ac appliance or tool. As I check out the chargers here at home and at the shop, almost every one of them has contacts which you could easily touch with your fingers. These are Makitas, DeWalts, Bosch, Craftsman, and others which are not name brands. One of the Craftsmans is built in such a way that I can't touch the contacts.

I will have to stand by my argument that if it's possible to get a finger on a contact, then the device should not be built without full isolation from line voltage.

I've seen a lot of different chargers, but I've never seen one that isn't isolated.

No, I don't have a 'recent' charger. The newest one I have is about 2 yrs old to me- I think these have been on the market for about 4 yrs or so.

There's the AA nmh chargers that are newer- all of those that I have you can easily touch the contacts-

Maybe those non-isolated chargers are not sold in Canada-

[Black_Moons]

Even if a charger is not heavy and has no wallwort, It still can be isolated, SMPS can be tiny (Just over a square inch is common for the smallest of 120v ac isolated smps)

Its also really a pain to safely draw and regulate more then a few mA without using a transformer to step down the voltage, And while isolation costs a little more, I have seen smps that where built outta only a handful of discreat components and 1 small 3 pin IC and 1 optoisolator.. Inside a computer power supply for the 5v standby power, No less.

That said, maybe the reason only one of your chargers is properly guarded, is that its the only one that does not have proper isolation?

[J Tiers]

Regular DeWalt DW9116 charger. Quite typical of several I have been inside of,.

Plain ordinary smps "buck" regulator. The green coil is a simple single winding coil, the one in the background is the mains EMI filter.

A buck type regulator is a fine device, but offers zero input-to-output isolation, in fact the circuit common is the same for input and output sides, so the battery is "live" when being charged.

You can see that it is guarded perfectly acceptably per first photo. And you can see the entire lack of any "transformer" in photo 2. The unit is UL and CSA listed.

http://img.photobucket.com/albums/0803/jstanley/dewalt_1.jpg

http://img.photobucket.com/albums/0803/jstanley/dewalt_2.jpg

[Black_Moons]

Ahhh I see now, Its not just a 'proper guarding' but its a totaly diffrent battery contact style then what I am used to that allows proper guarding to be made easily, Like a standard mains plug.

I am used to the batterys with contacts on the sides.

[J Tiers]

Yes, the side contact types are , I believe, ALL transformer isolated.

Typically they are simple chargers with a voltage limited transformer and a diode being almost the only parts, as with a weed whacker charger...... Some have more "innards" to them with proper limiting and sensing of full charge.

Simple chargers kill many batteries.

[Black_Moons]

Simple chargers kill many batteries.

Definately! Never ever buy anything with a '12 hour' charger, as they are usally by far the dumbest and often have no shutoff at all and are basicly just a trickle charge with you removing the battery after 12 hours (assuming you only charge it when its dead) is the only thing that keeps it from ruining the charger.

Generaly, Anything with a 2 hour charger or faster is going to be a 'smart' charger and will likey make your batterys last much longer just because its 'smart' and actualy turns off when done if you forget the battery in there, Its also rather hard to detect full state of charge with Nicad and Nimh unless you fast charge them due to the way its detected.

[bborr01]

I also noticed on my DeWalt batteries that one of them has an extra contact on it. Don't know what it is for.

Brian

Standard battery (xr or xr2)
http://i400.photobucket.com/albums/pp89/bborr01/Mobile%20Uploads/20120221_192828.jpg

Battery with extra contact (xrp)
http://i400.photobucket.com/albums/pp89/bborr01/Mobile%20Uploads/20120221_192923.jpg

[Iraiam]

I also noticed on my DeWalt batteries that one of them has an extra contact on it. Don't know what it is for.

Brian



Most times the batteries with the extra tab are made to be fast charged, the extra tab usually goes to the (- negative) in the middle of the pack, so the battery can be charged as 2 separate batteries.

I recall something about so many cells wired in series having issues when fast charging, namely the charge voltage must be higher, which is hard on the cells.

[Iraiam]

Definately! Never ever buy anything with a '12 hour' charger, as they are usally by far the dumbest and often have no shutoff at all and are basicly just a trickle charge with you removing the battery after 12 hours (assuming you only charge it when its dead) is the only thing that keeps it from ruining the charger.

Generaly, Anything with a 2 hour charger or faster is going to be a 'smart' charger and will likey make your batterys last much longer just because its 'smart' and actualy turns off when done if you forget the battery in there, Its also rather hard to detect full state of charge with Nicad and Nimh unless you fast charge them due to the way its detected.

Yes, because the charger is actually putting to much current into the battery. Most modern NiCd and NiMh batteries have what is called c/10 overcharge protection, (some cheap off brand cells are just inferior). c is the cell capacity in milliamps.

take a 2800ma battery. 2800ma/10=280ma. Generally if you charge at a rate less that c/10 (280ma) you can leave the charger on the battery for extended periods of time without damage.

Now calculate 280ma*12hr=3360ma. Pretty close when you factor in efficiency losses, The closer to full charge the battery gets, the harder it is to get them to take an additional charge.

[hermetic]

Got this off "The blokey Shed" aussie website, used it on my dead drill battery and it worked fine.
You need a mig welder or other high current DC power source. attach the negative lead (sometimes the earth clamp sometimes not, you need to know) to the POSITIVE battery terminal, disable the wire feed and turn off the mig gas, set the mig to about 20 to 30 amps and apply the positive of the mig to the NEGATIVE battery terminal, pull the trigger and keep pulsing the current into the battery till the spark you get with each pulse stops getting smaller (it will start with a fairly large spark, and then get less at each pulse) when the spark isnt getting any smaller, reverse the connections, positive of welder to positive of battery, negative of welder to negative of battery and repeat till there is virtually no spark. clean up the terminals with a wire brush, and charge the battery. Works like a charm! usual safety precautions apply no responsibility will be accepted if you blow your goddam head off, but I did mine, it was very undramatic, and it worked! you dont need to let masses of current flow through the battery, just keep pulsing till the sparking virtually dissapears, then reverse and repeat, then charge and off you go.
http://theblokeyshed.com/forums/showthread.php?14162-Fixing-****ed-battery-drills&highlight=drill+batteries

[rohart]

hermetic, that sounds interesting. But, you say apply the positive of the mig t6o the negative battery terminal (1st time round, that is). If you mean touch, then with the earth lead touching too, you get no spark. To get a spark you need a gap. If you mean a gap, what kind of gap ?

Unless you shove in so much current you're melted half the terminal, of course.

A constant current device, told to stick 30 amps through something, is going to try to stuff 30 amps through that something. 30 amps through a rechargeable is going to melt something.

[Boostinjdm]

A MIG machine is also CV, meaning you don't "set it for 30 amps".

[wb2vsj]

Got this off "The blokey Shed" aussie website, used it on my dead drill battery and it worked fine.
You need a mig welder or other high current DC power source. attach the negative lead (sometimes the earth clamp sometimes not, you need to know) to the POSITIVE battery terminal, disable the wire feed and turn off the mig gas, set the mig to about 20 to 30 amps and apply the positive of the mig to the NEGATIVE battery terminal, pull the trigger and keep pulsing the current into the battery till the spark you get with each pulse stops getting smaller (it will start with a fairly large spark, and then get less at each pulse) when the spark isnt getting any smaller, reverse the connections, positive of welder to positive of battery, negative of welder to negative of battery and repeat till there is virtually no spark. clean up the terminals with a wire brush, and charge the battery. Works like a charm! usual safety precautions apply no responsibility will be accepted if you blow your goddam head off, but I did mine, it was very undramatic, and it worked! you dont need to let masses of current flow through the battery, just keep pulsing till the sparking virtually dissapears, then reverse and repeat, then charge and off you go.
http://theblokeyshed.com/forums/showthread.php?14162-Fixing-****ed-battery-drills&highlight=drill+batteries

These tricks do work (And I've done it too), but have a limited life. If the battery chemistry is shot, nothing will help it. Game over! :)