XIAO nRF52840 - Recharging 3V 18650 battery?

Hi guys,

If I understand correctly, this XIAO can recharge batteries through the VIN, right ?

1- In this case does it have to be 5V rechargeable batteries ? Or can I use 3V 18650 ?
2- Any super reliable battery you would recommend for this XIAO ? I need 800-1000ma . Should I use camera batteries ?
3- Any way to use a rechargeable magnet/induction plug on the XIAO ?
Thank you

For XIAO nRF52840 has a dedicated battery charger BQ25100 for the BAT+ and BAT- pin, which could used for charging 1 cell Li-Ion/Li-Polymer battery.

Q1: It support to charge 1 cell Li-Ion/Li-Polymer battery which the Battery charge voltage (Max) is 4.2V

For Q2 and Q3 I do not understand what your are looking for.
Q2: You have mentioned 800-1000ma current rating for what is purpose and usage?
Q3: Use a rechargeable magnet/induction plug on the XIAO for what is purpose and usage? is it for supplying power to XIAO?
Please check the datasheet of the bq25100 chapter 7 Specifications, it listed out the ratings about the charging chip.

Works GREAT! 18650 lasts for weeks…LOL
GL :slight_smile:

Sorry @PJ_Glasso where can i buy your dev board? thanks

On the seeed website it’s available now. :grinning: :+1:
GL :slight_smile:

Hi Everybody,

Is there a way to charge the battery with just connecting the battery through the 5V pin ?
Or it’s just going to discharge the battery but never charge it ?

The Seeed Studio XIAO nRF52840 uses a charger IC BQ25100

The document shows the output of the charger:

that’s for
Battery Connection. System Load may be connected.

The bq2510x has a single power output that charges
the battery. A system load can be placed in parallel
with the battery as long as the average system load
does not keep the battery from charging fully during
the 10 hour safety timer.

So, it’s probably connected to the 5V pin too.
That’s how the battery must power the Seeed Studio XIAO when it’s not charging.

That must look like this

I’m looking for the schema that will show me that information.
Any idea where I could find this ?

That must be there maybe:

So if you connect a battery to 5V pin (VIN),
and plug the USB, the battery will be charged directly by the USB 5V and not through the charger
because the USB connection will make the MOSFET non conductive
and therefore, there won’t be a connection with VBAT.

Is this correct?

That sounds like a bad idea.




This is the power supply part taken out from the schematic. Can this help you?

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What was the mAh capacity of your battery?
Was that a standard battery with the connector that suits the expansion board?
Any link to the battery you used?
Thanks :slight_smile:

Thanks for the clarification.
I mistook VIN for the 5V path.

If a battery is connected to 5V (I’ve seen some people doing that on some video),
if the USB is plugged,
the device will actually draw power from whatever has higher voltage.
If you use a 3.7V battery, the device will draw power from USB and the battery won’t discharge.

But yes a diode would be a good advise,
to prevent damage to the battery in case it’s not a rechargeable battery
or even if it’s a rechargeable battery because there would be no connection to the charger controller.

So, I guess bottom line is that a rechargeable battery should be connected to Bat+ only
and a non rechargeable battery could be connected to 5V pin and adding a diode.

I haven’t bought the XIAO yet.
But I would use a LiPO 3.7V battery.

There is a voltage regulator as msfujino pointed out.
And it looks like it can take 5V and convert it to 3.3V

On the website, it shows:

Power 3.3V/5V DC

For general I/O pins:
Working voltage of MCU is 3.3V . Voltage input connected to general I/O pins may cause chip damage if it’ higher than 3.3V .

For power supply pins:
The built-in DC-DC converter circuit able to change 5V voltage into 3.3V allows to power the device with a 5V supply via VIN-PIN and 5V-PIN.

It’s the same on the other model (with battery charging capabilities):

Hi Philgib,

If you want to know everything on battery and battery charge I recomand to look at: https://batteryuniversity.com/

You dont need a 18650 to get 1000mA out, it exist flats one which should be much smaller.
One parameter which is important is the C-rate and how much peak current you need. Generaly for a 1000mAH battery you can get 1000mA peak load and charge it at max 1000mA (to simplify). But for drone application you can found battery with 20C discharge current (but price is not the same!).


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It’s a standard 18650 3.7V 1200mah capacity , I commandeered it from a broken BLE speaker :grinning: makes the expansion board last long time… :stuck_out_tongue_winking_eye:

here is a better picture

GL :slight_smile:

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Thanks for info on capacity of your battery.
I didn’t know if the expansion board charger could handle larger batteries.

I am scratching my head, having little knowledge in electronics but I would like to learn ( almost 60 years old, hopefully not too late…).

First of all, thank you so much guys for your help.

I am in love with tiny Seeeduino and I would like to connect a 5v 300ma DC motor ( a little windmill educational animation ), AND a rechargeable battery…
I believe 300ma is a lot and certainly too much for the Seeeduino.

=> I would like NOT to use the expansion board but straight solder cables to the Seeduino
=> Can I get 5V from the Seeeduino with a 3.7V rechargeable battery connected to the 3.7V port ?
=> Would you suggest a simple way to connect the 3.7v battery, the Seeeduino and the 5V motor without frying the Seeeduino ?
=> I am getting lost now at how I can recharge that 3.7 battery without the expansion board

Thanks a lot :smiling_face_with_three_hearts:

Hi philgib,

=> Can I get 5V from the Seeeduino with a 3.7V rechargeable battery connected to the 3.7V port ?

It is not possible.

=> I am getting lost now at how I can recharge that 3.7 battery without the expansion board

Once XIAO is connected to USB, the 3.7V battery is automatically charged.

=> Would you suggest a simple way to connect the 3.7v battery, the Seeeduino and the 5V motor without frying the Seeeduino ?

XIAO cannot drive a motor directly. A 5V-300mA or higher motor driver(FET or transistor) and a power supply are required.

Hi philgib and I’m 62 :grin: So that’s just a number,
May I make a suggestion for the physical portion. Try these smaller grove shields very flexible

The ziff socket is up on my thingiverse “Xiao”
GL :slight_smile:

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