AA vs D of the same mAh rating, are they same thing in total performance?

[Ocracoke]

I have a 3 D cell flashlight modified for square wave output, not that it matters, just needs fat D cells, posted FYI.

Recharging D, buying them, the expense, the singular use of the Ds over the AAs, is a pain. I rather bulk buy AAs for price breaks.

If you get a D cell adapter, to house AAs, lets say for argument, you buy the same mAh as the Ds, is it the same?

Don't Ds have more material, volume, within the same mAH rating of AAs, so this would imply more storage? Or is it moot, mAh is the same no matter what volume the cell, i.e same run time?

The D adapter I am looking at can house 1,2,3 AAs.

Clearly this is an advantage, sharing the mAh load over multiple cells? So that would be a huge plus, especially using the circuit that is producing the square wave has a sharp voltage cutoff. You get a warning of low voltage, but you need a certain voltage to drive the circuit, no fading of light, just cuts off.

Many thanks.

 

[jabe1]

A typical D battery is rated at 20,000mah, AA 2500mah.
So, three AA will be 7500mah. At higher current loads, their ability to drive an led drops dramatically, as the ratings are for 1.5v.
I would recommend nimh batteries instead. The initial investment is greater, but they can typically be charged 1000 times or so.

 

[snakebite]

a real high capacity nimh d cell will have lower internal resistance than an adapter and 3 aa nimh.
important for high performance lights.
3 cells=6 more contacts to potentially fail.
most of us already know how problematic 3aaa holders can be in cheap lights.

 

[fivemega]

You need to specify what kind chemical batteries you are going to use and what is purpose of replacing 3AA instead of "D". If you are using NiMH batteries, single "D"cell will have more capacity but if purpose is to have LSD and can't find in "D" size cell then 3AA is the only choice.
If you are using 3AA alkalines you will have more current delivery compare to single alky "D"
What is your main goal and what is maximum electrical current of flashlight.

 

[Chicken Drumstick]

I have a 3 D cell flashlight modified for square wave output, not that it matters, just needs fat D cells, posted FYI.

Recharging D, buying them, the expense, the singular use of the Ds over the AAs, is a pain. I rather bulk buy AAs for price breaks.

If you get a D cell adapter, to house AAs, lets say for argument, you buy the same mAh as the Ds, is it the same?

Don't Ds have more material, volume, within the same mAH rating of AAs, so this would imply more storage? Or is it moot, mAh is the same no matter what volume the cell, i.e same run time?

The D adapter I am looking at can house 1,2,3 AAs.

Clearly this is an advantage, sharing the mAh load over multiple cells? So that would be a huge plus, especially using the circuit that is producing the square wave has a sharp voltage cutoff. You get a warning of low voltage, but you need a certain voltage to drive the circuit, no fading of light, just cuts off.

Many thanks.

Lets take a step back.

1 D cell = 1.5v
1 AA cell = 1.5v

(assuming normal alkaline such as Duracell batteries).

The difference is the D cell has a higher mAh rating.... this is capacity. Think of it like the fuel tank on a car. The bigger the capacity, the more fuel and longer it will last. But it will offer pretty much the same performance otherwise.

Running batteries in Series will give you higher voltage, but the same capacity. e.g.

3 x D cell = 4.5v and approx 15,000mAh (different brands may have slightly different capacities).

If you used a 1AA to D cell adaptor you could run 3 AA in Series, this would still be 4.5v but only approx 2500mAh. So your runtime would be significantly less. However may still be sufficient for your needs, depending on what they are exactly.

You can also get 2AA to D cell and even 3AA to D cell adaptors. Which would give you a corresponding boost in capacity. But ultimately still likely less than a regular D cell.


If you are considering using AA batteries in D cell adaptors your best bet would be to use rechargeable NiMH batteries such as Sanyo Eneloops. As they will allow you to continually reuse them.