# How do I calculate power consumption? *confused*

Hi,

I have a circuit which is powered with 8x 1.2v/2700mAh akkus. So I have 21600mAh.

My circuit draws about 1mA when it sleeps and about 200mA when it runs. I want it to run 100 days without recharging, so I have 216mAh per day. That means 1 hour of 216mA or 24hours of 9mA.

So I can use 9mA per hour, which means that my circuit is allowed to run 4% of an hour. (200*0.04+1*0.96 = 8.96) 4% are 2.4 minutes.

Is all of that correct?

thanks fabian

I have a circuit which is powered with 8x 1.2v/2700mAh akkus. So I have 21600mAh.

You only have this much power available if you connect the batteries in parallel, which is something you should not do. If you connect them in series to give 8 * 1.2 = 9.6V you only have 2700mAH.

sigh

but the rest is correct?

200mA when it runs

That's a lot of power when it's running for something that could presumably get away with only running for about 2 minutes per day. What is it?

Could you invest in a small solar panel and have some nice NiMh batteries charging up during the day?

Mowcius

it's the arduino ethernet shield which is sucking that much.

if i could chose now i would use xbee or something that uses less power, but it's just a small university project and I don't want to invest more time and resources.

it should run 5 minutes every hour.

Well surely if it has ethernet you could provide it with power...

Mowcius