Arduino Forum

Using Arduino => General Electronics => Topic started by: amundsen on Feb 10, 2013, 07:40 pm

Title: Detecting when a LiPo battery connected trough a step-up board has low power.
Post by: amundsen on Feb 10, 2013, 07:40 pm
Hello,

I have a 5V Pro Mini Arduino I intend to connect to a 3.7V Lipo battery trough a step-up board (http://dx.com/p/lm2577-dc-3-5-18v-to-dc-4-0-24v-voltage-step-up-boost-module-red-154906 (http://dx.com/p/lm2577-dc-3-5-18v-to-dc-4-0-24v-voltage-step-up-boost-module-red-154906))

I would like a LED to be lit when the battery is getting empty. Can I connect the battery to an analog input of the Arduino trough a resistor and detect when the value decreases under a specific voltage threshold ? Or is there a better way to do it ?

Thank you in advance.
Title: Re: Detecting when a LiPo battery connected trough a step-up board has low power.
Post by: retrolefty on Feb 10, 2013, 07:56 pm

Hello,

I have a 5V Pro Mini Arduino I intend to connect to a 3.7V Lipo battery trough a step-up board (http://dx.com/p/lm2577-dc-3-5-18v-to-dc-4-0-24v-voltage-step-up-boost-module-red-154906 (http://dx.com/p/lm2577-dc-3-5-18v-to-dc-4-0-24v-voltage-step-up-boost-module-red-154906))

I would like a LED to be lit when the battery is getting empty. Can I connect the battery to an analog input of the Arduino trough a resistor and detect when the value decreases under a specific voltage threshold ? Or is there a better way to do it ?

Thank you in advance.


That should work, and there is no real reason to use a resistor as a analog input pin is high impedance and will not draw any significant current from the battery. A reading of 3.0vdc is a generally used common value to stop drawing current from the lipo cell to prevent cell damage.

Lefty
Title: Re: Detecting when a LiPo battery connected trough a step-up board has low power.
Post by: amundsen on Feb 10, 2013, 08:01 pm
Great. Thanks retrolefty !
Title: Re: Detecting when a LiPo battery connected trough a step-up board has low power.
Post by: MarkT on Feb 10, 2013, 10:06 pm
I'd include the resistor, something like 1k to 10k is fine, just to prevent the risk of accidental short(*) on the traces of the Arduino
grounding the LiPo - massive currents would then flow, vaporising pcb traces.  LiPo's can put out 50 to 100A or more if abused...

(*) Accidentally put the board down on top of something metal for instance.