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### Topic: How to calculate for how long a battery will last with Arduino code (Read 2046 times)previous topic - next topic

#### Pringles

##### May 11, 2013, 11:32 pmLast Edit: May 12, 2013, 02:08 am by Pringles Reason: 1
I got my Arduino Uno powered from a 3.7V battery, when I connect the Arduino to the battery the voltage from the battery drops from 3.70 to 3.69 being 0.01V of total drop.

I'm currently measuring the volts of the battery powering the Arduino with the Arduino itself. The reason is for when the battery drops to 3.0V an alarm triggers.

So, I already got the input battery voltage. How can I then calculate for how long the battery is going to last?
What other type of information/measures I need to get a 'X time left to 3.0V' ? Perhaps is only math from here?

In addition (just a note), I want the Arduino for example to calculate how long is going to last from 3.7V to 3.0V because I don't want my Arduino running lower than 3.0V.

Thanks!
Feel free to leave any questions!
I ask here how to change a light bulb, I get answered with a question, what color is the light bulb ,or what do you need the light bulb for? get a flashlight.

Rick & Morty, nailed it!

#1
##### May 12, 2013, 12:00 am
Do you have access to an ammeter?  If you want a good idea how much current YOUR project is drawing, go down to Harbor Freight Tools and buy a \$5 multimeter.

That being said, the tests have been done by others.  If your project is similar, you could at least get a good idea.

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

#### Pringles

#2
##### May 12, 2013, 02:04 am

Do you have access to an ammeter?  If you want a good idea how much current YOUR project is drawing, go down to Harbor Freight Tools and buy a \$5 multimeter.

Yes, I have a multimeter. I've have measure the voltage drop of the battery when I connect Arduino and it's from 3.70V to 3.69V dropping only 0.01V.
Now that I know how much my complete project drops, what do I do next?
P.S. I edited the post above with more specific details. Thanks!
I ask here how to change a light bulb, I get answered with a question, what color is the light bulb ,or what do you need the light bulb for? get a flashlight.

Rick & Morty, nailed it!

#### retrolefty

#3
##### May 12, 2013, 02:46 am
Well you need two pieces of information to estimate or calculate the duration from the battery. First is the mAH rating specification of your battery cell and second the current consumption drawn by your arduino. You do this second reading using your meter in it's current reading function (in series) not by reading the battery voltage with the meters voltage reading function.

Lefty

#### Pringles

#4
##### May 12, 2013, 06:48 am

Well you need two pieces of information to estimate or calculate the duration from the battery. First is the mAH rating specification of your battery cell and second the current consumption drawn by your arduino. You do this second reading using your meter in it's current reading function (in series) not by reading the battery voltage with the meters voltage reading function.

Lefty

My battery mAH is 1400 and 3.7V.
How do I know how much current consumption is my Arduino drowning*?
Assuming that I got those two pieces of information, what would be the arithmetic/math?

Thanks!
I ask here how to change a light bulb, I get answered with a question, what color is the light bulb ,or what do you need the light bulb for? get a flashlight.

Rick & Morty, nailed it!

#### AWOL

#5
##### May 12, 2013, 07:46 am
You need to measure the current draw using your ammeter.
"Pete, it's a fool looks for logic in the chambers of the human heart." Ulysses Everett McGill.
Do not send technical questions via personal messaging - they will be ignored.
I speak for myself, not Arduino.