MT12 -shuts down on first power up attempt

[pitts-mo]

Is there an existing issue for this problem?

• I have searched the existing issues

What part of EdgeTX is the focus of this bug?

Transmitter firmware

Current Behavior

The RadioMaster MT12 radio (currently v2.11.3) will shut down on first power up attempt when internal ELRS is enabled for the current model and TX battery is less than ~6.9 volts.

-Powering up a second time usually results in a working EdgeTX session.
-Selecting a model without internal ELRS before shutdown or setting switch positions to trigger warnings on boot will prevent the MT12 from powering off and result in a working EdgeTX session.

Expected Behavior

MT12 EdgeTX to power UP on first attempt if TX battery voltage in normal operating range of 6.6-8.4V.

Steps To Reproduce

1. Set current model to use internal ELRS (even just 10mw and backpack off)
2. Manage TX battery to voltage to value between 6.6 and 6.9 volts
3. turn off radio and let it stay off for a few minutes
4. attempt to turn on radio (MT12 shuts off immediately after boot sequence)
5. attempt to turn on radio (usually MT12 will boot on second attempt -capacitor charged?)

Version

2.11.3

Transmitter

RadioMaster MT12

Operating System (OS)

Linux

OS Version

No response

Anything else?

I suspect the root cause is a quirk of hardware design. However, I am not the only one to observe this and I suspect timing of powering on the internal module could provide a fix for this.

[3djc]

Hardware if anything. Doesn't happen here at at all. You should monitor your lipo volatge (with an oscilloscope or logic analyser with analog input) when that happens. if they are somewhat flaky, they could drop well bellow that value because of the current pull

[pfeerick]

*Might also be worth checking if the calibration is accurate, as the voltage of the cells could be lower than what you think it is. *

…

On Sat, Dec 13, 2025 at 5:21 PM 3djc ***@***.***> wrote: *3djc* left a comment (EdgeTX/edgetx#6874) <#6874 (comment)> Hardware if anything. Doesn't happen here at at all. You should monitor your lipo volatge when that happens. if they are somewhat flaky, they could drop well bellow that value because of the current pull — Reply to this email directly, view it on GitHub <#6874 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ABJ66KMWJPHRVLYLILXZP534BO46PAVCNFSM6AAAAACO3EZQUSVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTMNBZGA3TCNBZGE> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[pitts-mo]

Thank you both.
Testing with alternate battery packs and a bench supply I began to suspect this issue may be related to the stock MT12 2x18650 battery holder. First guess is battery side contacts.

In my testing I also observed internal MT12 voltage reading drops ~0.09v compared to voltage at back of input source connector when internal ELRS was on 150hz @250mw VS both internal and external RF off. So I recommend calibration of the MT12 voltage be performed with both internal RF and external RF off so the internal voltage reading will report even lower under load.

I will build some additional test tools and try to narrow down the weak point in the 2x18650 holder before I close this.

updated: corrected 0.9 drop was actually 0.09 volt drop