How much current does a flashlight battery offer?

It depends. For AA cells, the digital cameras draw more than a half amp at times. D cells can handle much more than an amp. If you want the batteries to last longer, then the current drain should be less. We're talking about alkalines here.

Here is what you need to know.

acell Alkaline MN1300 1.5V 14AH D "D" CELL Duracell Alkaline MN1400 1.5V 7.0AH C "C" CELL Duracell Alkaline MN1500 1.5V 2.45AH AA "AA" CELL Duracell Alkaline MN1604 9V .565AH 9V "9V" SIZE Duracell Alkaline MN21 12V .038AH CAR ALARM REMOTE BATTERY Duracell Alkaline MN2400 1.5V 1.1AH AAA "AAA" CELL

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al

"wylbur37" wrote in message news: snipped-for-privacy@posting.google.com...

Two seperate ratings involved. The 'current' is limited by the internal resistance of the battery, the resistance of the load, and by the way the chemistry behaves. A dead short across even a AA battery, can produce currents over 10A, for a short time, with some battery designs (NiCad in particular). Yes, the available current does rise with battery size, with more volume for the chemistry, and areas/thicknesses for the electrodes. The second rating, is the mAHr rating. This gives a figure for how much current can be delivered for how long. This figure is normally based upon the current that will discharge the battery in 10 hours. So a battery with a 1000mAHr rating, should be able to deliver 0.1A, for 10 hours. Now a typical AA Zinc-Cabon battery might offer perhaps 1000mAHr, while a D cell will perhaps offer 4000mAHr. Note that the latter implies a 'test' current 4 times as high as that used on the smaller battery. Some battery chemistries function better at high discharge rates than others. So (for instance), a NiCad D battery, may well support operation at 50* it's 'ten hour' current, and still give perhaps 25% of the full capacity, while designs like zinc-air, will only deliver low currents, even into a dead short. When multiple 'capacity' versions of the same battery exist, the extra capacity is often gained at the cost of other features. So (for instance), on NiMh batteries, where versions with higher capacities exist, these often show higher internal resistance (so will work less well at high loads), and increased 'self discharge' rates (they will run down quicker when not in use). A typical zinc-carbon D cell, delivering half an amp, will run for perhaps

4 hours. A high quality alkaline manganese dioxide battery into the same load, will top 20 hours. The internal resistance of the D cell, will typically be less than 0.2ohms, while the AA of the same type, may well have an internal resistance over 0.4ohm. Generall, AA batteries offer some of the best volumetric, and gravimetric power output (pack the most 'power' into the least weight, and volume).

Best Wishes

GP 3000/3300 Sub C NiMH cells (not quite typical flashlight batteries) have been used in model aircraft to power motors drawing 150A+ (yes that's One hundred and fifty Amps). In shorts bursts I should add.

One team had a few cells explode - not surprising really.

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In my experience, the opposite is true. The newer high capacity AA Ni-MH cells of 2000 mAH and higher have very low internal resistance, and last longer in my digital camera than the older ones. And digital cameras, especially mine, with autofocus and flash, use a lotta current, probably much more than an amp at times. You might think, why does he seem to imply that the length of time has something to do with the internal resistance? Well, in this case, when the four AA cells start to get discharged, the camera starts to do things like shut off the LCD while the flash is recharging. And it takes longer to 'boot up' the camera when the batteries are low. Finally the camera's LCD won't come on and the battery symbol just flashes. Time for another set of freshly charged AA cells. But the cells aren't discharged that bad, their internal resistance has just gone up.

Yeah, that seems to be the case. I've left charged batteries in my camera case for a couple months and I notice they last a lot shorter time in the camera. So now I'm putting a post-it on the battery carrying case with the charging date. And I check them and recharge when they've sat around a couple months.

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Batteries are rated in amp-hours, which is the amount of current that can be supplied for an hour (within a certain range). Even the lowly AA alkaline can probably supply over an amp for brief periods, a D will be capable of much more. When you get talking rechargeables some of them can supply tens of amps.

Non-Nicad cells are rated in Milliampere-hours, but the rate of discharge is very restricted, and I doubt you would get anything near an amp out of them due to the high internal impedance. They are designed for very low discharge currents.

Nicad cells are a different beast, and up to 20 or more amps can be drawn short-term, in fact we have had battery pack links melted through short-circuits.

I seem to remember that D cells are 4.5AH in Nicad and 15000 mAH in Alkaline-Manganese, 0.6AH for AA Nicad and 1500mAH for A-M. In all cases the Alkaline cells are much higher in nominal capacity, but that capacity is only available at very low discharge rates.

Peter

-- Peter & Rita Forbes snipped-for-privacy@easynet.co.uk Engine pages for preservation info:

Way more than that even. 70A is possible and recent Sub C size NiMH cells have been used at 150A (4 second bursts every 20 seconds until empty)

Many years ago I knew someone who worked at a cell manufacturing company. There was, ahem, a certain amount of leakage at the gate. After his car battery died, he used 6 "A" sized cells connected in series to start his Volkwagen. Yes, it was in the days when they used the 6V battery system.

Al

I have a 50 amp full scale (panel type) ammeter with heavy copper sheet about 2 inches long attached to the terminals. Applying this dead short to a 2100 mah AA Panasonic NiMH, I get 40 amps! I can well believe that if you do this for long, you might get a burst cell.

Go have a look here for the alkaline type cells:

and here for the NiMH cells:

It's interesting to note that the internal resistance of the D alkaline (173 milliohms) is larger than than that of the AA cells (146 milliohms).

It's also interesting to note that the volume of a D cell is 6.9 times that of an AA cell, and the capacity of an alkaline D is 6.3 times that of an alkaline AA (numbers taken from the Energizer site).

But the capacity of a NiMH D cell is only 3.7 times that of a NiMH AA cell (calculated using 8500 mah for D cells, and 2300 mah for AA cells, currently near the state of the art).

It looks like the battery folks have been really working hard to squeeze more into the NiMH AA cells.

Think of a hollow cube, 1 inch on a side. Now take a bunch of 1 inch by 1 inch metal plates, .1 inch thick. 10 of them will fit in the cube, and with each plate having a surface area of 2 square inches (neglecting the edges), this will give a total of 20 square inches of plate surface area in the cube. Now increase the size of the cube to 2 inches on a side, and increase the plates to 2 by 2 inches. Now each plate has a surface area of 8 square inches, and 20 of them will fit in the cube for a total of 160 inches of plate surface area in the cube. The bigger cube has 8 times the volume of the smaller and

8 times as much plate surface area will fit in the bigger cube. This same principle also holds if the plates are wound in a spiral and pressed into a cylinder, so the exposed surface area is in fact directly proportional to the volume of the container.

Hi...

Think of capacity not in terms of volume, but rather as a function of exposed surface area.

Ken

At the Energizer web site I referenced in another post, they say that the internal resistance of a fresh alkaline AA cell is .146 ohms. When I short a fresh alkaline AA cell with my 50 amp meter, I get 11 amps, just about what you get when you divide 1.5 volts by .146 ohms.

a D will be capable of

That and most rechargeable "D" cells are really just sub-C or even AA's in a D shell. You can get real D cells but they're expensive.

Baloney! They're putting _less_ into the D cells! The D Ni-MH cells that I've seen are just AA cells inside D sized shells.

AA

Exactly. They give you 1/4 the capacity for 1/2 the price. Simple economics - make more $ for less.

That's the same thing that they are doing with the "USB 2.0" cables. Nobody realizes that that the USB 2.0 signals were intended to work over

1.0 and 1.1 cables.

AE6EO

Some yes, some no.

It looks as if the Energizer DNH2 is a 2200-mAh AA-type cell in a D jacket... at an online price of $7 each at one dealer. YUCK.

On the other hand, the "Powerizer NMH9500" from ZBattery.com is a 9500 mAh battery, for $6 each.

Sometimes, you do _not_ get what you pay for!

--
Dave Platt                                    AE6EO
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