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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!

Robbe
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2 Answers2

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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

Bra1n
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    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? – Robbe Dec 31 '19 at 16:18
  • 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. – Paul Dec 31 '19 at 17:42
  • Do you recommand a specific charger? – Robbe Jan 01 '20 at 15:07
  • Because I don't know any, I've never seen or used them. – Robbe Jan 01 '20 at 17:38
  • You could use https://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. – Dave X Jan 23 '22 at 22:10
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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.

Duncan C
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    I don't think my battery has it. I bought this battery https://www.banggood.com/nl/Mobius-2-Camera-3_7V-820mAh-1S-LiPo-Battery-p-1105886.html?rmmds=myorder&cur_warehouse=CN and this charging module https://www.banggood.com/nl/TP4056-1A-Lipo-Battery-Charging-Board-Charger-Module-Mini-USB-Interface-p-1027027.html?rmmds=myorder&cur_warehouse=CN. I was thinking to buy this converter https://banggood.com/DC-DC-Step-Up-Step-Down-Module-2_5V-15V-To-3_3V-5V-Output-For-RC-Drone-FPV-Racing-Multi-Rotor-p-1303385.html?rmmds=wishlist – Robbe Dec 31 '19 at 20:07
  • Yeah, you need a smart charging module then, as Paul says in a comment on the other answer. – Duncan C Dec 31 '19 at 20:32
  • What do you mean? – Robbe Dec 31 '19 at 20:47
  • I mean that you should not use a dumb charger to charge a lipo battery. You need an intelligent charge controller. – Duncan C Jan 01 '20 at 00:06
  • I'm sorry but what has the charger to do with reading the lipo's voltage with the arduino? – Robbe Jan 01 '20 at 00:08
  • What do you hope to accomplish by reading the battery voltage? It won't change until the battery is dead. – Duncan C Jan 01 '20 at 02:02
  • I will connect a screen where I want to display the battery level so I can seen when I need to recharge it. I thought I could do this by comparing the battery voltage to its minimal (3.7V) and it's maximal (4.3V). – Robbe Jan 01 '20 at 11:39
  • That's the problem. It's my understanding that lithium chemistry batteries maintain a nearly constant voltage until they are almost completely exhausted, so measuring the voltage is not useful for gauging charge level. – Duncan C Jan 01 '20 at 12:02
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    On this website the show the percentage of capacity in function of the voltage read from the lipo so it should be possible? https://www.google.com/amp/s/blog.ampow.com/lipo-voltage-chart/ – Robbe Jan 01 '20 at 12:19