Why do we use 3 AAA instead of 1 or 2 AA batteries? Is there a huge output difference?
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Both AA and AAA have the same voltage output. It’s just a matter of size and capacity. You can put AAA in a AA device and it would still work
Voltage is important. Many electronics circuits need just above 3-4 volts to function properly, and dc-dc conversion is a often more expensive than just requiring 3 battery cells in series.
In series, each one is about 1.5V so that’s 4.5V.
Although AAs might have higher energy capacity, their voltage is still 1.5V each. You’d need three AAs for the same voltage, but then you’d need a thicker device to hold them.
Almost all of the batteries at the store, A, AA, AAA, C, D, they all have the same voltage. To get a higher voltage you have to chain them positive end to negative end. That’s why batteries are normally placed in alternating directions in a device.
So 3 AAA batteries gets more voltage, and that is important for some applications.
Can I tack a question on to this? Can double AA batteries provide more current than triple?
AA and AAA batteries are essentially, electrically the same, other than AA batteries are bigger so they last longer. AA’s are not “more powerful” they are just basically AAA’s that last longer as far as their construction is concerned.
The big reason for choosing AAA is for size restrictions. If you are making something thin, you might choose AAA to avoid having to to use the thicker AA batteries.
Most likely this is the case: The device needs a voltage, say 4.5V. Batteries are about 1.5V, so you need three batteries. Using 1 or 2 won’t work, voltage too low. Whether it’s AAA or AA depends on how much power the device needs to draw, usually balanced with the room the device has for batteries.
The 3 AAA batteries are in series to give 4.5V out for the device. While AA would have more capacity they have the same voltage, so 2 AA would only give 3V out, which probably isn’t enough for the device.
The amount of batteries you use sets the voltage – each AA or AAA cell produces 1.5v, and this voltage adds up, so if your device runs on 4.5v, you can chain together three 1.5v cells to make 4.5v.
The size of the batteries sets the battery life – an AA and AAA battery are essentially the exact same thing, only an AA is a little larger – this allows it to contain more chemistry, so it produces a bit more power.
So the quick rule is that a designer will choose the amount of batteries based on the voltage needed, and the size is a balance between battery life and physical size.
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