# Single AA versus double AAA - design question



## newlight-06 (Jan 25, 2008)

Running the mAh numbers (2850 versus 1250x2 for Energizer aa and aaa Alkaline) it looks like a single AA can power an LED longer than two AAA. Is it as simple as the math makes it look? 

In ideas how successful would a boost circuit like LM2623 be at driving an LED (like the Rebel) with a single AA versus using 2 AAAs? ... driving it at 3 plus volts for x amount of time.:shrug: 

Any help is very much appreciated!


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## Thujone (Jan 25, 2008)

It is slightly more efficient to run a boost circuit off of 2.4v than 1.2 but where on earth are you getting 1250mah aaa? hi cap sanyos are 1000mah and lsd cells like eneloop are 750mah...


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## paulr (Jan 25, 2008)

Those mah ratings are for alkalines but they are measured at very low currents. They might apply to running a single 5mm led but not to anything much brighter (like a Rebel).

1AA running a powerful led through a boost converter is one of the most popular designs on CPF these days, starting with the First Run Arc LS but popularized mostly by the Fenix L1p and its progeny. There are very few 2AAA lights in significant use here.


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## LEDninja (Jan 26, 2008)

Some random thoughts:

1AA - There are a lot of lights out there already. Just buy one of them. The only missing model is simple 2 level with a bright high and a low low (3 lumens or less).

2AAA needs to sit vertically in a pocket so you need a pocket clip. I have Sino Union LED drop ins in penlights, Nuwai TM-311H (River Rock 2AAA) and a TLE-20 in a 2AAA minimag but never carried them. Too long.

Why not 1AAA? Runtimes range from 11 hours (Fenix E0) to 0.5 hours (Kai buckle light)

Both 1AAA & 2AAA require a boost circuit in a tiny 10mm diameter board.

Why not your old idea of 3 or 4 AG13 or 2 2016?

BTW Nichia has the DS model LED out. about 2X brighter than the CS model you were recommended 2 years ago.

One more comment: Looong runtime but very dim LED lights are sooo 1990s. The 1 LED 3AAA Garritys and 4AA Dorcys are disappearing off the store shelves.


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## warlord (Apr 27, 2008)

If I'm not mistaken... 

2 AAA batteries contains 3,000miliwatts of energy in series or parallel configuration, using the values 1.2V and 1250mAh.

1 AA battery contains 3,420miliwatts of energy. using the values 1.2V and 2850mAh.

So @ 3.6V that would give you a *theoretical* 950mAh with a AA and 833mAh with AAA; minus driver inefficiencies. Alkalines would be a poor choice for this project due to voltage sag, you would probably be better off with NiMH.


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