Why aren't D batteries stronger than AA's?

[rickypanecatyl]

I confess I'm a complete idiot on these things but I was just wondering while shopping for rechargeable nickel metal hydride batteries why the highest amps I could find were 2.5 for AA, C's and D's - they're all 1.2 volts ... am I missing something? Shouldn't a battery the size of a D cell have more "something" than a AA?


While I'm asking my ignorant battery questions, is there a big difference in brands of CR123's? The reason I ask is because the price difference I see is huge! At Wall Mart for instance usually the best price I see for a single 123 is $6.00 (I'd understand it being more expensive at a gas station) but then on line I see cells for $1.50 ... are those cells just as good? Are they all the same size, all 3.0 volts but maybe the more expensive ones have more amps possibly?

Thanks for clearing this up for me!

rick

 

[Lynx_Arc]

I would ask you what are you going to use a battery for? there are AA nimh you can get over 5 amps out of and nicd subCs I think that are used in car starter packs capable of 100 amps. voltage is determined by chemistry not size while capacity is related to size.

 

[rje58]

I am no expert, but I believe what D cells have over AA cells is capacity, ie. runtime... I'll leave that for others to discuss.

Yes, many of the CR123A's you see online for $1.50 (or less) are just as good as the expensive CR123's you see at retail stores... it's just that since the retail stores sell tons of AAA, AA, C and D cells and very few CR123's, they charge thru the nose for these 'specialty' batteries.

I confess I'm a complete idiot on these things but I was just wondering while shopping for rechargeable nickel metal hydride batteries why the highest amps I could find were 2.5 for AA, C's and D's - they're all 1.2 volts ... am I missing something? Shouldn't a battery the size of a D cell have more "something" than a AA?


While I'm asking my ignorant battery questions, is there a big difference in brands of CR123's? The reason I ask is because the price difference I see is huge! At Wall Mart for instance usually the best price I see for a single 123 is $6.00 (I'd understand it being more expensive at a gas station) but then on line I see cells for $1.50 ... are those cells just as good? Are they all the same size, all 3.0 volts but maybe the more expensive ones have more amps possibly?

Thanks for clearing this up for me!

rick

 

[Mr Happy]

I confess I'm a complete idiot on these things but I was just wondering while shopping for rechargeable nickel metal hydride batteries why the highest amps I could find were 2.5 for AA, C's and D's - they're all 1.2 volts ... am I missing something? Shouldn't a battery the size of a D cell have more "something" than a AA?

I think you have your terminology a bit messed up. When you say 2.5 amps, what you really mean is 2500 mAh, which is a measure of the storage capacity of the cell. Yes, it's true that when you look in shops you will see C's and D's with a capacity of only 2500 mAh. This is because they put a small battery inside the big case and fill the rest with padding. Two reasons for this are: (1) to keep the price down; (2) to make the batteries compatible with normal chargers.

You can indeed get C and D cells with higher capacities up to 12,000 mAh, but these have to be bought online, they are much more expensive, and you will need a better and more expensive charger for them.

While I'm asking my ignorant battery questions, is there a big difference in brands of CR123's? The reason I ask is because the price difference I see is huge! At Wall Mart for instance usually the best price I see for a single 123 is $6.00 (I'd understand it being more expensive at a gas station) but then on line I see cells for $1.50 ... are those cells just as good? Are they all the same size, all 3.0 volts but maybe the more expensive ones have more amps possibly?

The on-line cells at $1.50 are exactly the same quality as long as you buy a brand like Duracell, Panasonic or Surefire. They have a big retail markup in Wal-Mart because they are a low volume item when sold in ordinary retail shops. When you buy them on-line you buy them in boxes of 100's.

 

[Bones]

As an example of the first type of cell mentioned by Mr Happy, NaturalNews cracked a 2500mAh Energizer D-cell and found a sub-C cell inside:

http://www.naturalnews.com ... News Target_NiMH_Batteries

...


...

 

[rickypanecatyl]

Yes, it's true that when you look in shops you will see C's and D's with a capacity of only 2500 mAh. This is because they put a small battery inside the big case and fill the rest with padding. Two reasons for this are: (1) to keep the price down; (2) to make the batteries compatible with normal chargers.

You can indeed get C and D cells with higher capacities up to 12,000 mAh, but these have to be bought online, they are much more expensive, and you will need a better and more expensive charger for them.

QUOTE]

Thanks - that clears things up a bit! Are capacity and mAH the same thing? IE going along with what you are saying, at the front of Wal Mart the other day I noticed AA, C & D rechargealbe NiMH Energizer batteries and they were all 2,500 mAH. So that means those batteries all had the same capacity right and were probably as you say just filling space inside the shell?

I must say I am impressed with the power to weight ratio of my new Makita LiIon cells. They weigh a little less than 2 D cells, are about the size of 2 1/2 D cells and they are 3,000 mAH/18 volts. Just to check my math, 3,000 mAH/18 Volts would be a battery 18X more powerful than a 1.2 volt/2,500 mAH right?

 

[rickypanecatyl]

Sorry 1 more question for you - why do Alkaline batteries have 1.5 volts and NiMH 1.2? Related to flashlights doesn't that make them burn dimmer?

Do they have any AA LiIon rechargeables online?

 

[Lynx_Arc]

Sorry 1 more question for you - why do Alkaline batteries have 1.5 volts and NiMH 1.2? Related to flashlights doesn't that make them burn dimmer?

Do they have any AA LiIon rechargeables online?

alkaline batteries are rated at that voltage at low power consumption while I think originally nicad an nimh rechargables were for heavier loads. nimh typically operate at about 1.35v resting awhile off the charger and under a heavy load can have a higher voltage than alkalines. Go to the marketplace if you want 14500 lithium ion (AAs) there is no 1.5v~ lithium rechargeable out there they are 3.6v~ rechargeables or non rechargeables 1.7v lithium primaries.

 

[Mr Happy]

I must say I am impressed with the power to weight ratio of my new Makita LiIon cells. They weigh a little less than 2 D cells, are about the size of 2 1/2 D cells and they are 3,000 mAH/18 volts. Just to check my math, 3,000 mAH/18 Volts would be a battery 18X more powerful than a 1.2 volt/2,500 mAH right?

Yes, a rough estimate of the energy stored in a cell is capacity times voltage, so the Makita battery pack has:

E = 3 Ah x 18 V = 54 Wh (watt-hours)

Whereas the NiMH cell has:

E = 2.5 Ah x 1.2 V = 3 Wh

So yes, the Makita pack has 18x the energy storage. Note that the Makita pack is not a single cell, it is I think 5 or 6 cells in series.

Another performance measure of a battery is instantaneous power output. Power tools are usually fitted with batteries that can supply a lot of current without sagging, even at the cost of some capacity.

You can buy lithium ion cells for your own use, but generally only from specialist online suppliers or from the CPF marketplace. You have to be very careful with them as they require a rigorous charging regime and a lot of care in use. If you get something wrong you can easily make a fire and cause a lot of damage or personal injury. Do lots of reading up on the subject before you consider going there.

 

[Magic Matt]

Sorry 1 more question for you - why do Alkaline batteries have 1.5 volts and NiMH 1.2?

A battery is a collection of one or more cells.

The chemistry of the cell dictates the voltage it produces, and how that responds to a load (being given work to do).

You could have a D battery at 5.1V if you were to make it from 3 x Lithium primary cells connected in series.


(Personally I dislike Lithium cells as I'm frightened they'll go if there's more than one in the circuit)

 

[Mr Happy]

Sorry 1 more question for you - why do Alkaline batteries have 1.5 volts and NiMH 1.2? Related to flashlights doesn't that make them burn dimmer?

This is just a convention that manufacturers have chosen to use when labeling cells. Alkaline batteries don't really have 1.5 volts and NiMH cells don't really have 1.2 volts. All cells have a variable voltage depending on their state of charge and the amount of current they are delivering. It's complicated, but most of the time you won't see a difference between an NiMH cell and an alkaline cell in use, except that for powerful lights the NiMH will usually be brighter than alkaline.

 

[SilverFox]

Hello Rickypanecatyl,

Another way to look at the difference between Alkaline and NiMh chemistry is that Alkaline cells are voltage rated at the beginning of their discharge, and NiMh cells are voltage rated half way through their discharge.

Alkaline cells start at about 1.5 volts, and their voltage drops off from there. The drop off ends up being close to linear.

NiMh cells actually start at around 1.3 volts, and half way through their discharge they are at 1.2 volts. They drop from 1.3 volts quickly down to around 1.2 volts, then they tend to hold around 1.2 volts up until they are completely discharged, then they drop voltage rapidly.

This paper was written by a CPF member. In it there is a comparison of the discharge curves of an Alkaline and NiMh cell.

Note that the lower the load the higher the actual voltage will be, so "nominal" values are very general.

Tom

 

[matrixshaman]

One other thing I don't think has been mentioned is that many LED flashlights used 'boost' circuits so depending on the design of the circuit you may have exactly the same brightness from a 1.2 volt battery as you would from a 1.5 volt or even a 3 volt battery. Most LED's need around 3.5 volts roughly so the driver circuit boosts the voltage as needed. There are lights that can take a variety of batteries though and some of them are indeed brighter with higher voltage batteries while others may not be brighter due to the regulation circuits.

 

[martheman]

What about voltage?

I confess I'm a complete idiot on these things but I was just wondering while shopping for rechargeable nickel metal hydride batteries why the highest amps I could find were 2.5 for AA, C's and D's - they're all 1.2 volts ... am I missing something? Shouldn't a battery the size of a D cell have more "something" than a AA?


While I'm asking my ignorant battery questions, is there a big difference in brands of CR123's? The reason I ask is because the price difference I see is huge! At Wall Mart for instance usually the best price I see for a single 123 is $6.00 (I'd understand it being more expensive at a gas station) but then on line I see cells for $1.50 ... are those cells just as good? Are they all the same size, all 3.0 volts but maybe the more expensive ones have more amps possibly?

Thanks for clearing this up for me!

rick

 

[Wrend]

Voltage is determined by chemistry type, state of charge, and sag during higher drain rates.

Basically, the voltage of cells that are the same chemistry type is the same regardless of cell size. (A 9V alkaline battery has 6 1.5V AAAA alkaline cells in series on the inside.)

Keep in mind that the voltage of a cell is not constant at different discharge rates and does not equal the cell's total power potential; it is only part of it, and that in turn is only part of its total energy.

Larger cells will typically have higher capacity and energy and often power due to there being more reactive surface area within the cell.

Smaller cells put inside larger cell sized cases, such as to be the size of a D cell, aren't what I would consider real D cells.