Read battery voltage from battery which is powering arduino

Question

I have a 5V arduino pro micro. I want to power it with a 3.7V lipo.

• Should I use a step up module to convert it to 5V?

I also want to measure the voltage of the battery.

• How can I do this?

Because I read that the power source also the reference voltage is so I cant measure it with an analog pin right?

I also use a lipo charging module to charge the battery.

Thanks for helping!

Answer 1

You can read the Arduino's supply voltage see here How to measure the supply voltage of Arduino without using an analog pin Alternatively use the internal 1.1V reference and a suitable voltage divider to read the lipo's voltage

• Robbe: I was just thinking if I use a step up module wouldn't the supply voltage be alwast 5V so I could use a analog pin without problems?
• aaa: Yes, if the output of said module is always 5V, best would be to use one of those charger boards with over-current and over-discharge protection. Or use a reference design.
• Robbe: Do you recommand a specific charger?
• Robbe: Because I don't know any, I've never seen or used them.
• Dave X: You could use arduino.stackexchange.com/a/50771/521 trick to calibrate the supply voltage, then measure the LIPO voltage on an analog pin and scale it appropriately.

Answer 2

Yes, you should use a boost converter to convert the 3.7V from your battery to the 5V that the Arduino requires.

As I understand it, measuring voltage to determine charge level does not work well with lithium chemistry batteries since they hold a nearly constant voltage until they are almost completely depleted. Generally lithium batteries include a chip that measures current in and out and lets you query their charge level.

• Robbe: I don't think my battery has it. I bought this battery banggood.com/nl/… and this charging module banggood.com/nl/…. I was thinking to buy this converter banggood.com/…
• Duncan C: Yeah, you need a smart charging module then, as Paul says in a comment on the other answer.
• Robbe: What do you mean?
• Duncan C: I mean that you should not use a dumb charger to charge a lipo battery. You need an intelligent charge controller.
• Robbe: On this website the show the percentage of capacity in function of the voltage read from the lipo so it should be possible? google.com/amp/s/blog.ampow.com/lipo-voltage-chart