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Wirecutter
03-12-2006, 08:24 PM
I'm rebuilding a rechargable battery pack today. All I could get on such short notice was the Radio Shock standard NiCads - the heavy duty ones must be discontinued. I'd use NiMH, but the charging circuit isn't built for them. Oh, and they're only about 8 times the price, too.

I needed a bunch of "C" cells, but they didn't have enough. Well I know a trick. (woof!)

Next time your in your local RS, note that, for standard NiCd batteries, the C and the D cell pairs cost the same and have the same capacity. Uh, yup, that's right. So, I grab one of the D packs, containing two of these:

http://mysite.verizon.net/vze8no8e/pics/orig_D.jpg

Next, it's down to the shop for a little surgery:

http://mysite.verizon.net/vze8no8e/pics/post-op.jpg

Lookie what's inside:

http://mysite.verizon.net/vze8no8e/pics/parts.jpg

Leaving me with this to assemble my battery pack - the "victim" is the cell standing up.

http://mysite.verizon.net/vze8no8e/pics/3cells.jpg

Well, it fixed my little problem, but caveat emptor, dudes.

-M

banjoallen
03-12-2006, 08:32 PM
Well I'll be damned....

Maker
03-12-2006, 08:38 PM
Awwww man....that ain't right! http://bbs.homeshopmachinist.net//eek.gif

tattoomike68
03-12-2006, 08:44 PM
That is wild , I would have never guessed that.

TECHSHOP
03-12-2006, 08:49 PM
I think you may have voided the warrenty.

------------------
Today I will gladly share my experience and advice, for there no sweeter words than "I told you so."

Kansas_Farmer
03-12-2006, 10:08 PM
No ****!! Look at them lazy bastards! Wow...

matador
03-12-2006, 10:38 PM
You weren't robbed,so rest easy http://bbs.homeshopmachinist.net//biggrin.gif.
These "C in a D case"were designed for older radio's(remember the ghettoblaster?)which used up to 8 D dry batteries.Since people didn't want to pay the price of "real"D-size ni-cads,which were up to 4 times the price of C cells,this little dodge came about.
A "real"D-size would have a minimum of 4000 Mah,and I believe they go as high as 8500 these days.But you pay for the privilege http://bbs.homeshopmachinist.net//smile.gif.

------------------
Hans

HTRN
03-12-2006, 10:49 PM
Batteries America (http://www.mrnicd-ehyostco.com/newpage3.htm) has NiCd D's for $8.95 for a 5000mAh. They have NiMH's that hold 8000mAh for $14.50. They'll add solder tabs for a dollar a battery.


HTRN

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This Old Shed (http://thisoldshed.tripod.com)

Mad Scientist
03-13-2006, 01:05 AM
At one time Radio Shack did have two flavors of “D” size batteries. The one that you have been abusing and a “full-bodied version”, which if memory is correct had a 4-amp hour rating. Apparently they have discontinued that one and replaced it with a NI-MH model that has a 4.5-amp hour rating.

The NI-MH's have more power BUT they will discharge themself even if they are not used.

thistle
03-13-2006, 09:37 AM
holy **** a pregnant battery!

pgmrdan
03-13-2006, 10:04 AM
At least it's not as bad as something I saw a few years ago where someone cut open one of the big name battery maker's 9 volt battery only to find 5 cells and a spacer instead of 6 cells. Yep, about 7.5 volts from a battery you pay decent bucks for expecting 9 volts. Thievery!

ahidley
03-13-2006, 10:26 AM
Wirecutter. The place to buy c size nicads is at a hobby shop for radio control cars

Take an old one with you to compair sizes to make sure they arent sub-c size, which is alittle smaller than c


[This message has been edited by ahidley (edited 03-13-2006).]

Wirecutter
03-13-2006, 10:38 AM
Yeah, I realized that it was the same cell with different packaging. I was mostly steamed because they dropped the heavy-duty C NiCd and went with the NiMH, which is something like twice the money, and 4-5 times the cost of the cells I bought. My application is made for the heavy-C. NiMH cells, as I understand, have different charging characteristics, and I wasn't sure the circuit I have would work correctly.

And of course, I was pressed for time. Next time I'm going to try something like batterymart.com. Online I can nearly always get things better and cheaper, but slower.

Mac1
03-13-2006, 11:22 AM
Ain't nothing changed. Back in the days of tube type radios, more tubes were better.But some radios came with lots of tubes that only lit up and did nothing.

Wirecutter
03-13-2006, 12:26 PM
<font face="Verdana, Arial" size="2">Originally posted by ahidley:
Wirecutter. The place to buy c size nicads is at a hobby shop for radio control cars

Take an old one with you to compair sizes to make sure they arent sub-c size, which is alittle smaller than c</font>

I thought of the hobby shop thing, but didn't have one as handy.

I know about the sub-C cells, though. I need those for the cells in the pack for my Milwalkee cordless drill. Last time I looked, they were difficult to impossible to find, unless I wasn't looking for them.

J Tiers
03-13-2006, 12:54 PM
NiCd batteries suitable for packs are available from Digi-Key electronics.

I haven't bought any recently, but I have rebuilt several packs with batteries from them.

Someone else suggested robbing them from an HF replacement pack. Cheaper than other sources, apparently.

The nice thing about the double-case deal is the inner ones come with long solder tabs. That's the problem with standard batteries if you want to build a pack, no solder tabs.

Mike Burdick
03-13-2006, 01:02 PM
Wirecutter,

If you (or anyone else) have time, can you show how the cordless battery pack is done? Milwaukee preferably. http://bbs.homeshopmachinist.net//smile.gif

Thanks...

_____________________



[This message has been edited by Mike Burdick (edited 03-13-2006).]

Evan
03-13-2006, 01:09 PM
I don't know if they still sell them but at one time Radio Shack also sold D cell nicads with a 1200 or so mah rating. They contained 3 450 mah AA cells in parallel. This was a bad idea as it tripled the chance of failure.

Mad Scientist
03-13-2006, 04:38 PM
Don’t know if this will help but if you are willing to use surplus batteries there is this local junk store that I visit now and again. They carry all sorts of neat nifty stuff and things. From toys to electrical parts, to mechanical parts, optics, chemistry stuff, and oh yes a whole shelf full of batteries, etc.

Being that merchandise is all someone else’s useless junk their prices are “generally” reasonable.

American Science & Surplus. www.sciplus.com (http://www.sciplus.com)

vinito
03-13-2006, 06:46 PM
Babooshka Franklin!

Wirecutter
03-13-2006, 10:36 PM
<font face="Verdana, Arial" size="2">Originally posted by J Tiers:

Someone else suggested robbing them from an HF replacement pack. Cheaper than other sources, apparently.

The nice thing about the double-case deal is the inner ones come with long solder tabs. That's the problem with standard batteries if you want to build a pack, no solder tabs.</font>

Oh you sure hit that nail on the head. This is the second time rebuilding this particular battery pack, and the tabs were pretty rough. After ripping them off the welds and a couple of soldering cycles... Anyway, you're spot on - and I used that tab material.


Evan -
I agree, the parallel cells is a particularly bone-head idea for a battery, and more than triples the likelihood of failure, IMHO. Connecting batteries in parallel requires either perfectly matched cells (yeah, right) or some way to isolate them from each other. Other wise they'll fight each other to the death.

Mike B -
Yeah, I can snap a few photos, but the tabs on my Milwalkee are a little stout for soldering. I'm afraid I'm going to have to get the welder working on that. I also need to research DigiKey again for that size. I have to determine exactly what size designation they have and then find some. As I said, last time I tried (about a year or two ago) I searched pretty exhaustively and had no luck. I don't recall now if it was that the battery size couldn't be found anywhere or that it was a strange non-standardized size.

I'm on the road at the moment, but I'll check on this when I get home.

Evan
03-13-2006, 10:48 PM
If the triple cell D cells still exist you can easily spot them. The negative end plate has three dimples in it in the form of a triangle that are the contacts to the cells inside. Avoid these unless you need some AAs.

DancingBear
03-14-2006, 10:36 PM
Wirecutter,
You aren't likely to find C size (as opposed to sub-C) at a hobby shop that caters to the R/C car crowd. Sub-C is the only legal size for most racing. There are also some of the 4400+ D-cells used for monster trucks. Mostly the racers have switched to Ni-mh, but there's lots of ni-cd's still around for more casual use.

You are correct about the charging circuit for Ni-mh, it is quite different, and Ni-Cd circuits won't do the battery any favors.

Walt

Your Old Dog
03-15-2006, 06:52 AM
Someone mentioned the Ni-mh didn't have as good a shelf life as nicads. That's not our experiance in my buisness. We can charge our Ni-mh's, go on two week vacation and come back to fully charged batteries (as indicated on the battery's meter). With Nicads we'd loose at least half power. Ni-mh also don't seem to mind cold weather nearly as much as Nicads do. And there is "no" memory affect in the Ni-mh batteries we use. I routinly shoot 10-15 minutes on a 45 minute battery and plop it up on the charger when I get in. Have used the same 3 batteries for over 1 1/2 years now with that routine and they are as strong as ever. IMHO Ni-mh is 10 times the battery that nicads are...

should also add that the Ni-mh batterys in my strobe lite see very little service but I can count on them to be ready for action if they've sat in a closet forl 6 months. Would never try that with a nicad.

[This message has been edited by Your Old Dog (edited 03-15-2006).]

J Tiers
03-15-2006, 09:17 AM
NimH batteries are extremely variable....

The ones in my camera last months. Last charged at Christmas, still going.

The Toshiba battery pack for my Satellite 1604 will last about 3 days. It is a NEW battery, and, the one it replaced is slightly better, lasts a week. That was why we replaced it.

Fully charged, battery indicator in the comp says fully charged, charger has turned off.

If I unplug and turn everything off, it will not even start after 3 days. Says dead as a melted doornail, charges it up.

Most NiCd would do FAR better than that.

Evan
03-15-2006, 11:26 AM
There is a lot of variability in the design of both nicads and NiMH batteries. Some nicads are specifically designed for extremely low self discharge and can hold a charge for years. The nicads on satellites have lasted as long as 20 years because of careful charge and discharge control.

NiMH batteries generally self discharge at about 25 to 30% per month. This is about double the rate of typical nicads. NiMH batteries have a much shorter lifetime if they are deep discharged. This is the opposite of nicads which should be discharged at least 80% before recharge.

Even when used properly NiMH batteries have typically less than 500-700 charge cycles before capacity drops to less than 80%. They also degrade to unusable condition if left connected to a load. If not in use they should be maintained at about 80% of full charge, not at full charge. If NiMH batteries have been left uncharged for a long time they will need conditioning by charging and discharging several cycles to restore capacity.

Nicads are available in many types. Sanyo makes the Cadnica S series that has almost no self dicharge but can only supply low currents. In general the higher the current the battery can supply per cell the higher the self discharge rate.

Self discharge is highly temperature dependent for all types. The difference for a nicad stored in the fridge to one stored at room temp is a factor of ten. At elevated temps it is much worse for all types.

About 15 years ago I bought about 20 4400 mah D cell nicads surplus for $1 per cell. They have no identification on them but they are some of the best batteries I have ever seen. Some of them are still good and I still use them.

Wirecutter
03-15-2006, 11:56 AM
<font face="Verdana, Arial" size="2">Originally posted by Your Old Dog:
IMHO Ni-mh is 10 times the battery that nicads are...
</font>

I have to agree. It's a bummer they can't benefit from the same charging circuit as NiCd. The capacities and lifetimes I've seen (except for in laptops) are much better with NiMH.

Evan
03-15-2006, 12:05 PM
The biggest difference between nicads and NiMH is the chargers. Cheap products usually use nicads and come with cheap chargers with no charging control. Leaving the nicads on charge overnight on one of these that is intended to fully charge them in 3 hours will damage the batteries the first time you do it.

NiMH cost more and cannot stand to be incorrectly charged. Because of that they come with chargers that properly control the charge cycles and don't damage the battery. Nicads, if properly charged with a good charger will outlast NiMH by a lot, have lower self discharge and some of the new types of nicads like the foam electrode types from Panasonic have the same capacity as NiMH cells.

[This message has been edited by Evan (edited 03-15-2006).]

Evan
03-15-2006, 12:19 PM
BTW, if you have a drill or whatever that has a cheap unregulated charger that fast charges the nicads you can add a power resistor to cut the charge rate to about 1/10 of the amp hour capacity of the battery. This will increase the charge time to about 16 hours but ensures that the batteries will not overheat and vent. As a general rule it is safe to leave nicads on a charge of 10% of amp hour capacity without venting from overheating as the gasses produced will have a chance to recombine in the electrolyte.

Mad Scientist
03-21-2006, 08:27 PM
Don’t know if you are still charged up about finding a replacement battery. But while looking through an electronics catalog I shocked when I accidentally made contact with the following (“D” size NiCad battery “5000” mAh)

Check out Jameco. Com. Part No. 244558CB @ $6.15 This is a “current” price.