Hello.
Are there any good pages for best practices for setting up a project with battery management? I’m using a Sense with a 4.2 LiH AA. I’m looking for advice, recommended circuits, best practices, etc. Power management (sleep mode), etc is welcomed too.
Thanks in advance.
Hi there and welcome,
Can you be more specific, which Sense the ESP32s3 Sense or the Xiao nRF52840 Sense ?
Both are awesome so you can’t go wrong. If I were starting at the battery which imo makes a lot of sense no pun intended 
Check out the battery life calc. [
](Battery Life Calculator | DigiKey Electronics)
PJ| Processor | ESP32-S3R8 Xtensa LX7 dual-core, 32-bit processor 240 MHz |
|---|---|
| Low Power Consumption Model | Light-sleep: ~ 2mA Deep Sleep: ~ 14 μA |
| WiFi Enabled Power Consumption | ~ 100 mA |
| BLE Enabled Power Consumption | ~ 85 mA |
| Working Temperature | -40°C ~ 65°C |
That’s great info. Thank you @PJ_Glasso !
I’m using the Xiao nRF52840 Sense.
Does one just connect the battery to the battery leads & charge through the 5v pin or USB connection? All the battery charging management just magically happens?
Hi there,
Yea, if it were only that easy…LOL
The Xiao has built in charge control chip, so if you use the usb for external connection to power it. The Xiao charges and manages the battery for you.(provided you use the BATT pads on the bottom of the PCB for connection. It doesn’t do that if you use the 5V pin connection.
HTH
GL PJ
On a similar vein, are rechargeable coin cells like the LIR2032 compatible with the nRF52840 sense power management chip? I need a very small battery footprint, so coin cells would be brilliant.
Any help appreciated!
Hi there,
After looking over the Spec sheet for the BQ25100 it can deliver 50ma or 100ma charge current
the LIR2032 has confusing specs, 40ma. ideal charge current , max 200ma supply current.
they are frequent recharge batteries. I would try it and I would but a temperature probe , nothing fancy even a IR-temp gun and see what the case does if anything, same rules for the battery management apply as far as drop out , OVP , temp. If you had access the app note shows how to RC it for lower charge current like 40ma. (Pg22)
I wouldn’t be afraid to try it, but it’s gonna drain fast if you spend allot of time awake, so DeeP sleep model code for that battery.
my .02
HTH
GL PJ
How is the circuit supposed to work? The battery negative and ground pin are not the same. Since that’s true, is the battery supposed to be completely isolated? That would suggest the Seeed is expected to regulate voltage for the rest of my project. And if so, what current can the 3.3V pin source?
I’m obviously missing something. The one wiki I’m aware of is on the Seeed site, but has scant information on battery usage. Is there something better? Just point me in the right direction.
Well here is the important Part LOL,
Actually they are the same level. GND is GND. battery Neg. is connected to pin 13 on Xiao.
Take a LQQk at the charge chip data-sheet there is a section that covers sinking current for external devices.
HTH
GL PJ
That’s very helpful. I thought I’d measured resistance between those two grounds. If that’s the case, though I wonder why even bother with the surface pad when a perfectly good pin does the same thing?
Please point me to the “charge chip data-sheet”. I definitely need to take a look at that.
Check this thread ,https://forum.seeedstudio.com/t/xiao-nrf52840-recharging-3v-18650-battery/268260/2?u=pj_glasso second post has the link for it, plus good info related to Batt.
HTH
GL PJ
