XIAO nRF52840 New units no longer power up from battery pins?

[Rafael_Simoes]

Hi Seeed team and community,

I own around 10 XIAO nRF52840 & Wio-SX1262 Kits (used with Meshtastic), all purchased earlier, and they power up correctly when supplied via the battery pins (VBAT/GND).

Recently, I purchased 2 additional kits from oficial store, and these do NOT power on when powered from the battery pins. They only seem to power up when USB is connected.

The wiring, battery, and test setup are confirmed working, since the older units still behave correctly under the same conditions.

This leads me to suspect that:

• There may be a hardware revision change
• The power management / VBAT path was modified
• Manufacturing defect?

Questions:

Has there been a hardware revision that affects battery power behavior?

Were there changes to the VBAT / power path or enable logic?

Is there a schematic or changelog documenting differences between revisions?

Is there a required firmware or pin configuration to enable battery power on newer boards?

If helpful, I can provide PCB photos, silkscreen revision markings, and voltage measurements to compare older vs newer units.

[PJ_Glasso]

Hi there,

Can you say what versions of Meshtastic you are installing and How?

HTH
GL PJ

[cgwaltney]

Welcome! and thanks for such a great detailed question

I will try to get the answer for you

can you please add a photo of the offending and non-offending units, front and back so we can

possably identify the revision dates can you confirm the same operation when the two boards are attached and when they are detatched?

[Rafael_Simoes]

(post deleted by author)

[Rafael_Simoes]

Tested both Meshtastic 2.7.18 / 2.7.17 via DFU

[PJ_Glasso]

Hi there,

Ok, Great , also if you put them each in Bootloader mode, Scan the contents of the UF2 on the drive Current.uf2 are they the same SD 1.140 or something?
Good place to start, Right out of the Bubble.

HTH
GL PJ

If nothing is connected, no possible strapping pin conflicts?
nothing on D0.

[Rafael_Simoes]

Here they are. Seems the same revision

[cgwaltney]

i think one more the bottom of a good one…

Soldering Basics

the flux makes the solder flow exactly to the metal.. its like crazy when you try it… the liquid just goes where its supposed to go like it has a mind or something… if you get the paste, it is like paste till you touch the heat and it turns to liquid… it is like a pathway for the solder and it just flows https://www.amazon.com/Solder-Wire-Rosin-Paste-Flux/dp/B08BLSJHW1 [Using Flux | Soldering Basics | Soldering for Beginners] [Do This Before You Solder Anything]

My personal XAIO NRF-LoRa sandwitch in a medical product bottle… Not the best solder job… but solid and made with flux and pre-tinned pads and not a thermal controlled iron and very bad tip… but the new tips are not compatable with my favorite radio shack iron set… what da?

[Rafael_Simoes]

@cgwaltney

sandwitch in a medical product bottle… Not the best solder job… but solid and made with flux

dont get me wrong, but I don’t believe the issue is my solder quality. on the photo that blob was made when desoldering.
Also, the xiao pre soldering light up the charging LED.. as is always consuming 225miliamps

[Rafael_Simoes]

They are both on sd 140:
Model: Seeed XIAO nRF52840
SoftDevice: S140 version 7.3.0