Lipo battery charger module for homemade Arduboy?

Is there any alternative of this battery charger module for homemade arduino?
The linked one looks very smart and it should handle everything. It would be fantastice if I can charge my homemade arduboy while plug it into USB for uploading new games or so.
I am searching but have never found good one for my pro micro. Most modules just handle charging.

  • Charging while playing (while it is plugged)
  • Charging while turned off (while it is plugged)
  • Auto switch to battery mode when unplugged
  • Auto switch to charge mode when plugged

These are the functions I would like to have.
Any information is very welcome!

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I was thinking one of these would make an ideal (albeit slightly expensive) basis for a homemade Arduboy, you get battery charging built-in plus a user-programmable RGB LED!:

…scratch that, just realised it is 3.3V @ 8MHz :roll_eyes:

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What about 2 modules?

Both connected to the lipo

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@MLXXXp, would this combination work with my Arduino 101 like we had discussed?

@crait, It could but you would lose some efficiency boosting to 5V then having the 101’s on-board regulator dropping it back down to 3.3V. You would have to make sure that the boost converter provides a properly regulated and clean 5V output.

Also, it may be necessary (or at least advisable) to make sure that you never power the 101 from both the 101’s USB connector and the boost converter at the same time.


You can get modules that combine a charger and a boost regulator, such as these:

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Yes but somehow they go from 2 USD shipped to 15 USD + s&h after being combined.

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Thank you guys for many valuable information!

So as @eried indicated using two module seem to be the most practical method then?
If that’s so, can we use Pro Micro’s usb port to supply power to lipo charger?

Also, the advice from @MLXXXp seems to be very important.

Also, it may be necessary (or at least advisable) to make sure that you never power the 101 from both the 101’s USB connector and the boost converter at the same time.

How do we make this happen? Do we need to add dedicated module which automatically decide where the units get powers from?

I am getting really confused…

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Just to let you know, you can only @-mention someone by their username.

(We really ought to write a manual for the forum.)


Ah, I got it, thanks!

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No, you need to separate that input. But that depends on the pro micro you are using.

Not really, what I would do is:

  1. Look for the trace from the USB VCC pin and cut it in the pro micro (the following image is just an example, I think in the pro micro is in the backside of the PCB)

  2. Attach the VCC from the USB to the input of the charger module.

  3. Attach the charger module to the lipo

  4. Attach the DC DC step-up to the lipo, wire that module to VIN in the Pro Micro (it would be ideal to remove the Pro Micro regulator, and just place a step-up to 3.3V directly, but I think the screen needs 5V, so this is a lazy wasteful solution)

No need for “switching”. I am not sure how healthy is that for the lipo, because when you are connected to usb, you will draw and recharge the lipo at the same time. But how often do you intend to play connected for a long time?

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I have never thought about cutting USB Vcc line of my Pro Micro! It’s smart!

Regarding to No.4, why do we need to remove the Pro Micro’s regulator? Mine is 5V 16mhz version and it seems there is no 3.3v output/input pin on the board.

Not sure how often I play it connected for a long time but I think I can add a hardware on/off switch between step-up and Vcc of Pro Micro. Then I think I can charge the lipo and play games at the same time when the switch is on. I can charge the lipo and turn other systems off by switching off. Am I correct?

Check the pcb, see if there is a regulator. It should be something like

Yes, you can do that. Better if you put the switch between the lipo and the step-up

@eried, I located the regulator on my Pro Micro.
What is the point of removing it? Is there any other reason for removing it other than reducing power consumption( this is what I get by googling) ?

does it need to be boosted to 5V?
so far I made homemade arduboy with 3.7V lipo battery connected directly to Raw pin on Pro Micro and it works fine for months. I even Tried it with 2 AA/AAA 1.5V battery and strangely it still work.

But still I don’t have a protection/switching circuit and it still a bit dangerous. And this problem @gedo831 are also my problem that keeps bugging me until now. Fortunately I have few alternative now thanks to this thread

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Yes, to reduce power consumption, but do not do it, I was just commenting that it would be the best solution.

Also, you can change from 3.3v logic mode to 5 volt mode by soldering or connecting the J1 pin on the Arduino Pro Micro


Not Connected is 3.3 Volt logic
Connected is 5 Volt logic


Does that bypasses the integrated regulator?

You can get similar cheap ones from China:

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No, you’ve got it backwards. The Pro Micro should be run a 5V (for the required 5V/16MHz version) and the display is better run at 3.3V (although most display modules claim to be 5V tolerant but many “cheat” by just using resistors instead of proper level converters).