Battery level indication : a circuit

[SEB]

Hey great idea!

I want to incorporate a small circuit like to to a 3.7v mod, I just want a led to light up when the batt goes low... When I press my switch to vape


But the way I see it op amps uses min 5v as supply. So how do you power up the op amp? Can it work with low voltage? should I use the battery as supply voltage or should I power it with the regulated 2.7v out of the zener diode?

-Can you also point me to a small single op amp?

-at what safe low voltage a normal 3.7v lithium should be charged? 3v,3.2v,2.9...???

-The blue resistors are used for lowering the Vin... what range of resistors would you suggest? 10k, 100k, 1m?

Thank you!

 

[kinabaloo]

Hey great idea!

I want to incorporate a small circuit like to to a 3.7v mod, I just want a led to light up when the batt goes low... When I press my switch to vape


But the way I see it op amps uses min 5v as supply. So how do you power up the op amp? Can it work with low voltage? should I use the battery as supply voltage or should I power it with the regulated 2.7v out of the zener diode?

-Can you also point me to a small single op amp?

-at what safe low voltage a normal 3.7v lithium should be charged? 3v,3.2v,2.9...???

-The blue resistors are used for lowering the Vin... what range of resistors would you suggest? 10k, 100k, 1m?

Thank you!

A single 'low' voltage would be about 3.4-3.5v

Quite a few op amps can operate fine with a low supply voltage, such as the LM358

The blue resistors can be around 10K total; maybe experiment with a trimming pot on a breadboard. Supply the op-amp direct fom the battery.

3v is a good point to stop use and recharge.

 

[SEB]

Thank you very much!!!!

Now I have to find my breadboard and my power supply! I have no clue where I put them at my parents warehouse