Why no rechargable "C" or "D"?

[elgarak]

I think the main reason that rechargeable C and D cells haven't caught on is that they simply don't have the power capacity and longevity of the better disposables. Electronics devices that use AA batteries are typically low-power-drain, so rechargeables will last a useful amount of time. Things like lanterns/flashlights are high-power-drain and will chew through rechargeables at a much higher rate than disposables. Not to mention that rechargeables leak current much more quickly over time than disposables degrade, so are unsuitable for emergency devices.

I respectfully disagree. Rechargeables work better in high current applications. Classic example is the electronic flash, which charges faster and provides more flashes with rechargeables than with alkalines. Modern regulated LED flashlights typically run longer on rechargeables than alkalines (one example).

Correct is the assessment of the high self-discharge making rechargeables unsuitable for emergencies, unless the device is plugged in with an intelligent charger and topped-off until the power fails. However, those devices still recquire regular maintenance and check of the batteries.

Rechargeables (especially Nickel based) are best suited for regular heavy use. For long-term storage and emergencies Lithium based primaries are better.

That's why C/D-rechargeables never catched on: Except for Maglites for police/night guards, few devices running on them see heavy, regular use (though most night workers nowadays switch to better Lithium powered flashlights or dedicated rechargeables; the Mag's light output and size is not up to date to technological advances; they're also taken away from police officers since they can be misused as clubs). Another factor is that C/D-rechargeables seldom provide the higher capacity their larger size could provide; a lot of rechargeable C-cells are just AAs in larger containers (AA and C have the same length).

 

[elgarak]

I was at the dollar store today and they had self-powered LED flashlights for a buck. Shake it for ten seconds and it stays lit for something like 15 minutes. The days of big batteries are numbered, I think.

I passed on those but could not resist for $1.79 a combination flexible LED penlight and laser pointer, complete with button cells. I mean, for $1.79, a pocket laser that makes a point you can see a quarter mile away! Gee Whiz!

Careful with that. Ironically, a lot of the cheaper shake-lights are fakes, in which the LED runs from a hidden coin-cell (Warning from flashlightreviews).

In fact, I think that one of the cheap coin-cell powered keychain lights is a better investment for emergency lights than shake-lights. Small, Li-cell which provides long-term storage, some are nearly indestructible.

 

["O"]

Radio Shack C/D batteries fraction of Thomas

???

Radio Shack stores have carried rechargable batteries for decades, in sizes ranging from AAA to D (plus 9v rectangular).

Radio Shack unfortunately only sells the pseudo C/D rechargeable cells of the type that Elgarak mentioned: each is just a single AA cell hiding inside a C or D sized can.

RS does sell chargers that work for real, full capacity C and D NiMH cells. These are available from the online source Thomas Distributing that someone already mentioned.

 

[Sagger]

I have a bunch of flashlights that take either C or D batteries. Yet all of these flashlights are wimpy compared to the high powered light that comes with my power drill and takes the same rechargeable battery that my drill takes.

 

[DRBUZZ0]

While in China they were giving away adapters to convert AA to C and D size, so I only buy AA and AAA bateries.

A quick Google found these:

[qimg]http://us.st11.yimg.com/us.st.yimg.com/I/starbattery_1912_1070503[/qimg]

[qimg]http://us.st11.yimg.com/us.st.yimg.com/I/starbattery_1912_1115965[/qimg]

There are probably more and cheaper ones if you have a look. (The Chinese ones were just a clear plastic shell that clipped together. Works fine)

.

You do realize that although the voltage is the same for AAA/AA/C/D batteries, the capacity is not. If you put a AA in a device which takes D's, you'll run it down pretty fast.

 

[elgarak]

Meadmaker,

Instead of trying to find C/D-rechargeables, I would recommend investing in modern LED lights, which provide longer runtime. There are lights out there which run ~30..40 hours on D-cells, with non-diminishing brightness. With AAs, you can get 4..5 hours of high brightness, or 10..13 hours with low brightness. Reduces the amount of replacement batteries a lot.

Personally, I like (and have lots of) flashlights that run on CR123A Lithium batteries, but I guess that most average campers balk at the costs of both the lights and the batteries (which cost up to $10 apiece locally, though can be had for $1.15 on the 'net).

The aforementioned flashlightreviews is a good place to start looking for lights. There's also a forum with very helpful people for recommendations.

One recommendation from my side for a good all-around flashlight is the Streamlight ProPolymer Luxeon (in both 4xAA and 3xC versions, ~$35 with batteries). Although Streamlight does not recommend it, the light also runs perfectly on NiMH rechargeables (the reason for the disapproval of NiMHs is that the light is safety-rated for explosive environments, while the NiMHs are not, but that's not a problem for camping). A nice lantern is the River Rock LED lantern, 4AAs, $20 in Target stores.

 

[stormer]

Seriously consider LED lighting

Or you can make a joule thief yourself.

I gutted a cheap china-made torch and put this circuit in. The LED lights with already run-down AA batteries for about 15 hours. Not the brightest light, but good enough.

 

[bruto]

You do realize that although the voltage is the same for AAA/AA/C/D batteries, the capacity is not. If you put a AA in a device which takes D's, you'll run it down pretty fast.

The links didn't work for me, but I'm assuming that the adapters arrange several little batteries in parallel, which would increase the capacity a good deal.

 

[ceptimus]

Putting NiCad (or NiMH) cells in parallel is NOT recommended.

These cells have a peculiar voltage vs charge curve. As they come up to full charge the curve flattens, and the voltage then falls slightly as more charge is added (partly due to the cell heating during charge).

If you connect freshly charged cells in parallel, then the cells will try to equalise voltage with each other, but because of the negative slope on part of the curve, this can result in a runaway situation. In exceptional circumstances this may even result in fire, but will more likely just partially discharge some of the parallel cells while damaging others by overcharging/overheating.

The one time when it's okay to connect Nickle cells in parallel is when you're about to discharge them fast. If you intend to put sufficient load on the cells to flatten them in, say, ten minutes, then the internal resistance of the cells means that they all only discharge, rather than attempt to transfer charge to each other.

 

[bruto]

Putting NiCad (or NiMH) cells in parallel is NOT recommended.

These cells have a peculiar voltage vs charge curve. As they come up to full charge the curve flattens, and the voltage then falls slightly as more charge is added (partly due to the cell heating during charge).

If you connect freshly charged cells in parallel, then the cells will try to equalise voltage with each other, but because of the negative slope on part of the curve, this can result in a runaway situation. In exceptional circumstances this may even result in fire, but will more likely just partially discharge some of the parallel cells while damaging others by overcharging/overheating.

The one time when it's okay to connect Nickle cells in parallel is when you're about to discharge them fast. If you intend to put sufficient load on the cells to flatten them in, say, ten minutes, then the internal resistance of the cells means that they all only discharge, rather than attempt to transfer charge to each other.

I didn't know that. Just curious, is that also a characteristic of the big NiCad batteries used in standby power applications at hospitals and the like? I had always assumed (but of course one can always make an ass of u and me that way) that they were capable of parallel connection. Those nicads are big, and liquid filled. Does this reduce the hazard, or are they still a poor candidate for parallel use?

I ask the above because I have heard that because these cells must be replaced on a schedule while they're still good, and because they're classified as hazardous material, some institutions give them away if you know whom to ask (unlike the phone companies which sell their superannuated lead-acid batteries). A friend got a bunch of big nicads some years ago, with the intention of using them for an alternate energy project, but he was pretty coy about the exact source, and I don't think he ever got around to setting them up before he died, but I've wondered about this.

 

[Meffy]

Radio Shack unfortunately only sells the pseudo C/D rechargeable cells of the type that Elgarak mentioned: each is just a single AA cell hiding inside a C or D sized can.

Could be. If so I've not seen them. The NiMH C and D cells I've bought there have much greater capacities than AA cells of the same type and brand.

 

[SkeptiKilt]

My source for rechargeables is greenbatteries.com. They have C and D cells that aren't just jacketed AAs. Your typical NiMH AA has a capacity of 2100-2500 mAh; their Cs are rated at 4500, and the Ds at 9000. They also have 9V NiMHs.

In their battery FAQ, they explain the lack of standard-size Li-ion rechargeables this way:

Lithium-ion batteries are not available in standard sizes. We believe this is because it would be too easy for users to inadvertently put them in a charger not designed for Lithium-ion batteries creating a potentially dangerous situation. (If an alkaline battery is put into the wrong charger it might leak or even burst, but a lithium-ion battery put into a NiCd or NiMH charger not designed for lithium-ion, might ignite.) Also, because Li-ion batteries operate at much higher voltage (typically 3.7V per cell) than the 1.2 to 1.5V of most cell batteries, designing a 1.5V lithium-ion cell would be expensive.

 

[Alareth]

Radio Shack unfortunately only sells the pseudo C/D rechargeable cells of the type that Elgarak mentioned: each is just a single AA cell hiding inside a C or D sized can.

RS does sell chargers that work for real, full capacity C and D NiMH cells. These are available from the online source Thomas Distributing that someone already mentioned.

Well let me check on that.

** Turns around to look at batteries hanging on the wall behind him **

Capacities on the batteries I sell here at the Shack are as follows:

NI-CAD

AAA - 300 mAh
AA - 1000 mAh
C - 2000 mAh
D - 2000 mAh

Based on that the C and D cells may have the same core but it isn't a AA

Ni-MH

AAA - 700 mAh
AA - 2000 mAh
C - 3000 mAh
D - 4500 mAh

Those varying capacities show no common core.

 

[Inquisitive Raven]

Could be. If so I've not seen them. The NiMH C and D cells I've bought there have much greater capacities than AA cells of the same type and brand.

AFAICT, the Radio Shack NiMH C and D cells are actually C and D cells. The same, however, cannot be said of the NiCads. The D's at least, are too lightweight. Although, IIRC, the Consumer Reports battery review that I read many years ago, before NiMH was an option, said that the D cells were C cells in larger shells.

 

[HeyLeroy]

Careful with that. Ironically, a lot of the cheaper shake-lights are fakes, in which the LED runs from a hidden coin-cell (Warning from flashlightreviews).

In fact, I think that one of the cheap coin-cell powered keychain lights is a better investment for emergency lights than shake-lights. Small, Li-cell which provides long-term storage, some are nearly indestructible.

Yeah, and give up my five D-cell Mag-lite? I can just picture it:

"Gimme your keys and wallet!"

"Stand back or I'll clop you with this puny little pocket flashlight!"

Jeez, I might as well smack 'im with my murse.

 

[elgarak]

Well, I define a emergency in this context as a situation where you need LIGHT when there's none, not a weapon.

Best is when you can use LIGHT as weapon, let's say with the insanely bright Surefire M6 (still way smaller than a Mag 5D), or the strobing mode of a Night-Ops Gladius.

 

[Meffy]

AFAICT, the Radio Shack NiMH C and D cells are actually C and D cells. The same, however, cannot be said of the NiCads. The D's at least, are too lightweight. Although, IIRC, the Consumer Reports battery review that I read many years ago, before NiMH was an option, said that the D cells were C cells in larger shells.

This agrees with the capacities Alareth provided.

 

["O"]

AFAICT, the Radio Shack NiMH C and D cells are actually C and D cells. The same, however, cannot be said of the NiCads. The D's at least, are too lightweight. Although, IIRC, the Consumer Reports battery review that I read many years ago, before NiMH was an option, said that the D cells were C cells in larger shells.

This agrees with the capacities Alareth provided.

Thank you Alareth for the providing the current Radio Shack facts. Nice to have an insider here!

To summarize, making my "pseudo C/D rechargeable cells" statement specific to NiCad and NiMH and correcting my AA remark:

-- The Nicads are pseudo D, not pseudo C:
RS's D size has only the same capacity of their smaller C size (2000 mAh).
But higher capacity than the AA.

-- NiMH
The RS NiMH C and D each has about half the capacity of NiMHs found elsewhere, so I call them pseudo C and pseudo D. (Example, D size has 4,500 mAh capacity vs 11,000 mAh found elsewhere.)

 

[bruto]

Careful with that. Ironically, a lot of the cheaper shake-lights are fakes, in which the LED runs from a hidden coin-cell (Warning from flashlightreviews).

In fact, I think that one of the cheap coin-cell powered keychain lights is a better investment for emergency lights than shake-lights. Small, Li-cell which provides long-term storage, some are nearly indestructible.

I was back at the dollar store where I saw these things before, and you're right. Sure enough, all the shake lights have a pair of coin cells, and not very hidden either, since they're all transparent at that store at least. I probably should have bought one for a buck and taken out the coin cells to see if it would still work.

 

[Zombified]

I suspect the reason C/D rechargables are harder to find is just economics; they probably don't sell nearly as well as AA or AAA and don't get carried. Downsizing of electronics...

Incidentally, LED lighting is a lot more efficient (and more reliable) than incandescent, provided you don't have any complaints about the color or spread pattern. There are some really good lights out there these days that get pretty decent light output out of 2 or 3 AA or AAA batteries or small lithium cells. These days I'd rather have an LED light with a couple lithium batteries (like a Surefire L2) than a 5 D-cell Maglite. Fewer and fewer reasons to bother with C and D cells...