How to monitor LiPo battery level

Other Hardware Sensors
1

Im using a 3S LiPo battery with a total of 11.1volts and 25-50c discharge current.
is there a way to monitor the battery level? Im using UNO
can I just plug in the battery directly to an analog pin?

2

at

I don't think that is a good idea.
But you could use a simple voltage divider to scale the battery voltage down.
Bat + -> 10K -> 10K -> analogInput -> 10K -> GND
should give you a 3rd of the battery voltage.
using 3x 10K shouldn't drain you battery very much but 10K value may be a bit high.

anyway check this tutorial.

3

do you mean plugging the batteries' negative terminal to the third resistor or plugging the batteries' negative to a GND pin on the arduino board or just connect the third resistor to a GND pin on the arduino board?

4

I tried just plugging in the end of the third resistor to a GND pin on the arduino board and it didn't worked as I suspected. Where should I put my batteries' negative terminal? Im afraid of shorting my batteries

5

I assumed that you would use common GND.

Yep, and connect the v- of the battery to GND as well.

Both. GND's should be connected to each other, The third resistor should be connected to GND.

How about you first connect all 3 resistors to the battery, measure the voltage between GND and the point that should go to the analog input pin. That should be around 3.7 - 4.2 v.
Now connect GND's (of board and battery) together, and connect the analog pin to the point between resistor 2 & 3.

7

Seriously ? Well that's a great help considering you have not added anything new to the conversation other than

We'll have to wait and see about that. But just adding a small capacitor will probably be enough if that happens.

8

Thanks for the help It works!
now I can read voltage and know when my LiPo is crying for food

anyways, I just found out that there is actually an example program hidden in Examples>Basics>ReadAnalogVoltage
and it does it perfectly with a very well explained code lol
the code is easy to adjust for our own voltage

9

@Deva_Rishi can you please edit your reply that I made as a solution
by inserting this

to let people know that there is a better and clearer code than the one that you gave me

10

I didn't give you any code, just a hardware solution.

11

I mean the code from the website that you gave me

12

Ah Ok ! i was also there not really focussing on the code, but more referring to the technical information. Code on instructables and many other sites like that is rarely very good, and in many cases just bad and confusing. Obviously IDE Examples are usually better. It is just rare that a good programmer will post on a site like that and many times we get confronted with requests to 'fix' or 'modify' that kind of code (Though actually i had a look and this one is extraordinarily bad.) Anyway there is a lot of details on LiPo batteries that is important, like charging and discharging. For monitoring the simple IDE examples explain quite clearly how to make it work.

13

3.7v doesn’t mean this is max v you get from the battery, more like 4.2, so if you don’t count that in and make voltage divider you can burn the ADC

14

The OP stated using an UNO, so a third of a 3 cell (11.1v) should be fine

15

looks like you missed my point, 3 cells can give you up to 4.25v each, and are normally charged to 12.6v and not 11.1v

16

I got that, but a third of 12.6v = 4.2v which is well within the 5v range. I really don't see why you think i missed your point. I considered it not relevant in this case. That is something else.

17

because I wasn’t talking about THE voltage divider you proposed, but A voltage divider, which could have any ratio, not 1:3, Also I don’t believe I was replying to you, pretty sure I pressed reply to the thread

18

Fine, but not very good with the ratiometric A/D of an Uno.
If you do that, then battery readout not only depends on battery voltage, but also on the supply variations of the Uno.

Much better do divider down to 1volt, and switch to the internal stable 1.1volt Aref in setup().
A 10k:120k divider also gives better protection against over-voltage.
Sketch can be as simple as this (untested).
Leo..

// 10k:120k voltage divider for 0 to about 14volt
// 120k from battery to pin and 10k from pin to ground
// optional: 100n capacitor from pin to ground

const byte batteryPin = A0;
const float calibrationFactor = 0.01364; // calibrate by changing the last digit(s)
float voltage;

void setup() {
  Serial.begin(9600);
  analogReference(INTERNAL); // switch to 1.1volt Aref
}

void loop() {
  voltage = analogRead(batteryPin) * calibrationFactor;

  Serial.print("Battery voltage: ");
  Serial.print(voltage);
  Serial.println(" volt");
  delay(1000);
}