Couple questions on battery use

Products & Technology XIAO
1

Hello all. Is there a way to connect a led to the onboard led to display the battery charge on the outside of a case that I am making? Would like to be able to see the battery charge indicator as the module will not be visible. Can the onboard led be mapped to another GPIO?

Also, is it safe for the charger circuit to hook up 2 18650 5000mAh batteries in parallel? Don’t want to overload the charger. TIA for any help.

2

It is very dangerous to use LiPo batteries connected in parallel.

The on-board red LED on the ESP32S3 only indicates that the battery is charging, not the remaining battery charge.
It is possible to write code to measure the battery voltage and display it’s status on an external LED connected to the GPIO. The battery voltage must be resistor-divided externally and converted to AD.

3

Its only dangerous if the batteries are not the same type and capacity. All kinds of devices use batteries in parallel. The question was if it would overload the charging circuit on the module.

As for the charging led all I wanted is the LED indicator either flashing or not so I know when the unit can be unplugged from the USB port when fully charged.

4

I think that connecting in parallel without a balancing circuit should be done with great caution. At your own risk!
S3’s charging circuit does not have the ability to charge batteries connected in parallel separately, but charges them with a maximum charge current of 110 mA until the battery pad voltage reaches 4.2 V. See the SGM40567 datasheet.

1 Like
5

Hi there,

Well that is only sorta true, "

Sure it can be done but is it SAFE?
Paralleling two LiPo batteries to power a Xiao ESP32S3 (or any MCU) can work, but only under specific conditions. If you skip the precautions, you can cook a battery or damage your board.

Do NOT connect two LiPos in parallel unless:

  1. They are identical in capacity, chemistry, and age
  2. They are at the same voltage (within 0.05V) when you connect them
  3. You understand the charging implications (the Xiao has a single-cell charger)

these are the baselines, FAFO will always be lurking so please be careful and mindful.
If you:

  • Use two identical 3.7V LiPo cells
  • Pre-balance them to the same voltage
  • Wire them in parallel, not series
  • Connect them to the BAT pads of the Xiao ESP32S3

→ Then yes, it works fine. You get double the capacity (mAh) while maintaining the same voltage. The Xiao’s charger chip will see it as a single larger battery.

:warning: Risks & Things to Watch:

Risk Explanation
:fire: Current surge If one battery is at 3.9V and the other is at 3.6V, the higher-voltage cell will dump current into the lower one — possibly overheating it.
:no_entry_sign: Charging safety The Xiao’s onboard charger (e.g., TP4056 or equivalent) is designed for 1S charging. Two mismatched cells could cause overcharge or imbalance.
:chart_with_downwards_trend: Lifetime mismatch Different internal resistances can cause one cell to age faster, which leads to early failure.

Other Suggestions to consider…

Safe Practices:

  • Balance them first: Charge both batteries to the same voltage (~4.2V full or ~3.7V nominal) before wiring them together.

  • Use a battery protection circuit (PCM/BMS) if you’re building this into a product.

  • If you plan to charge in parallel, the onboard charger must handle the combined current capacity and balance properly.

  • Better yet: use a parallel LiPo board or connector harness that’s made for this.

  • If you want extended runtime without parallel risks, use:

  • A single larger capacity cell (e.g., 1200–2000mAh)

  • Or a protected parallel battery pack (with built-in balancing)

HTH
GL :slight_smile: PJ :v:

The Xiao works great for the 1S configuration it was designed for ,I have several threads of demo’s & video’s of it being used in the real. Do take a peek at those.