LiPo battery monitor

Community General Discussions
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1

I haven't used LiPo before but I see that it needs to be monitored to make sure the cell voltages do not drop too low. The same is true with  LiIon.

I see two ways of handling this.

The first is to use an A/D on the Arduino DUE I am using and look at the total battery voltage (I have a 3S 11.1). That would be a cut out somewhere around 10V. There are a few problems there, you need a voltage divider to get below the 3.3V input limit. And then the A/Ds require a low impedance (2K or so) to be accurate, I am not sure if this is the case with the DUE but it is with the Atmel chips.

The second is to buy a LiPo battery monitor. I have one on the way that has the LED readout and a buzzer. The problem there is that this is on the charging line and does not provide direct feedback to the MCU.

So... How much leeway do you have between the battery falling to alarm stage and the ~3V that sends it to the recycle bin?

How is this typically handled in a robot?


2

Voltage Monitoring

Nice to see a post on this topic.
  1. TI (and others) make a number of voltage supervisors that could be used to trigger an interrupt on a digital I/O pin.
  2. Put an OpAmp between the voltage divider and the Analog in port.
  3. Use the high impedance voltage divider and increase the A/D sample time.
  4. Record the run time and manually reset it when you charge the battery.
3

Options

Thanks.

I like option 1:

http://www.ti.com/lit/an/slva385/slva385.pdf

I’l; look to see what is available.

Option 2 has merit as a single supply voltage follower, it wouldn’t have to swing to the rails, and running it off the same supply as the DUE would keep it safe.

Option 3 seems to be the easiest. I’ll look into the sample rate, I did not not know that you coud do that.