# Powering the arduino via battery pack

I have completed my Arduino Nano v3.0 project on a breadboard and now I am ready to move to the project enclosure box... So the question is now - power supply... how?

I have read some posts on the net and it left me a bit confused. So far this is what I got:

1) 9V would not be ideal since the regulator would burn off energi (as heat) regulating the 9V source to 5V. - and therefore be inefficient.

2) According to the specs - the board cannot transform up from below 5V to 5V. So below 5V is not a solution.

3) If I use a 4x AA battery-pack (6V) it would be in the aboslute low end of what the regulator accepts (and since the battery power will drop when they are drained the regulator might fail).

My initial thought was to use the 4x AA battery pack - but now the internet has confused me. help! :)

The current I will drain would typically be around 2 leds + arduino + lcd with backlight so my guess is 40mA + 30mA + 40mA = 110mA. Weekends would be 200mA ;-)

(oh! please note that my main issue is that I don't know whats right and wrong here...)

6xAA

The Arduino can actually run at 16 MHz on as low as 3.8V and at 8 MHz down to 2.4V. If you are not doing analog measurements your code probably doesn't even need adjusting. You hook the power to the "+5V" pin.

Multiply the power draw (200 mA) times the number of hours you want it to run between battery changes to get the minimum mAh rating of your battery. I think rechargeable AA cells run about 2000 mAh so would run your project for about 10 hours at a time.

To get lower power consumption you would want to have the processor sleep most of the time and to have the LEDs wink briefly every second or two instead of burning power continuously. Turn on the LCD backlight only when someone needs to read it in the dark (via push button or proximity sensor).

Nick_Pyner:
6xAA

But that is as originally, pointed out, inefficient.

As johnwasser points out, upwards of 4V is OK, so three zinc-alkaline AA or four Ni-MH fed directly to Vcc should be just fine - well it would be that is, except that the LCD requires a regulated supply no lower than 4.5V (for its “contrast” chain, not for its driver chip!).

So I suppose you are stuck with five zinc-alkaline AA or six Ni-MH, feeding the regulator. Two problems with sleeping are the regulator itself which draws significant quiescent current - far more than the processor - and the power LED.

You can efficiently power the Arduino at 5V with lower voltage batteries, like a single LiPo (nominally 3.7 V) using a step-up regulator like this one: http://www.pololu.com/product/2564

Or you can use just about any battery arrangement with a suitable step-up/step-down regulator, like this one: http://www.pololu.com/product/2123

I have a lengthy discussion about power usage here:

http://www.gammon.com.au/power

An example project using batteries:

http://www.gammon.com.au/forum/?id=12106

The current I will drain would typically be around 2 leds + arduino + lcd with backlight so my guess is 40mA + 30mA + 40mA = 110mA. Weekends would be 200mA

100 to 200 mA sounds like a lot. I try to aim for microamps.

I wouldn’t turn on LEDs or backlights until you need to.

You can use something like this one: Li-ion Battery pack with charger and monitor

If your project it’s a 3V or lower one, just add a LDO Regulator for your desired output voltage. If it’s 5V then use a standard step-up converter, they are very common today, working from 0.9V up to 5 and delivering a stable 5V output.