I've charged my 18650 's several times with the internal charger since I've had the T12 Pro.
It charges to 8.2 volts.
I've taken the 18650 li-ion cells out once to check balance and to charge on an "XTAR" battery charger I bought from racedayquads. The 18650's were only 00.1 apart in voltage.
( 4.2 Volts vs 4.1 Volts) They both charged up to 4.2 volts on the XTAR charger.
I use a 1.0 Amp usb ( iPhone type) AC adapter and the supplied usb cable .
NO issues so far.

I have confidence in the internal charger but I NEVER leave it unattended as a precautionary practice.

Thanks. I’ll give it a try and monitor the battery voltages. How long do you have it on charge?
Is there any way to tell when the charging is complete?

I have not seen a light or any other indicator to show the charge is complete.
I usually check by turning the T12 pro on after an hour and check progress.
Total charge time would be variable according to the mAh of the batteries.

Presumably the charge time would also depend on the cell imbalance. The charge circuit is presumably quite low current in both charging and discharging (for balancing), and I've seen such simple charge circuits take forever if there was any significant cell imbalance. I imagine they try to match cells carefully when manufacturing multi-cell batteries (like lipos), but individual 18650s might be poorly matched in comparison. In that case, it would probably always take quite a while to reach full charge of both cells.

Yay, at last the OpenTX is available that fixes annoying bug in this Jumper T12 Pro....DMA conflict. I couldn't install LUA scripts due to this. And it causes other issues like menus and SD contents disappearing.
I haven't installed it yet, i'll do this week. Thanks to Rjkrash for letting us know it was out - i was checking every few weeks.... and wmartoz for installing it and reporting back that it's fixed this DMA issue. The fixes are in 2.3.8 but a 2.3.9 was released soon after so probably best install that instead (it will contain the 2.3.8 fixes also).
https://www.open-tx.org/2020/06/13/opentx-2.3.8
https://www.open-tx.org/2020/06/14/opentx-2.3.9

Jumper T12: fix DMA conflict between SD and internal module
Jumper T12: fix an issue with curve edition in mixer screen
Jumper T12 Pro: allow multi trainer

Yeah, no indicator charging is complete and no instructions. Maybe someone can contact Jumper? I've asked on Aliexpress Q&A under Jumper T12 Pro just now 'official Jumper store', but don't expect a great response - response not as quick as banggood and not even sure my question will show up since there's zero q's on there right now.
This is my only 18650 charger.. I have a head torch that uses 18650's and even use the jumper to charge that lol, because i lost it's charger. I simply leave it charging for couple hours and then unplug it - seems to be fine. To check it's working you can; take a note of your battery voltage, then charge for 10 min, switch on Jumper again (you need to unplug the USB cable), and see the voltage of the batteries has increased.
BTW; the charge cradle holding the batteries does have 3 wires....so it's possible the internal charge circuit is balancing the two 18650's.

Hi,
I'm interested in this radio for something smaller than my T16 for my whoops, toothpicks running frsky receivers etc. Is the buzzing noise that comes from the loudspeaker always present when using internal module or only when an external module is plugged in?

I just checked. Buzzing noise is very faint and you have to put your ear to the loudspeaker. This noise only comes when i select my E011 (Bayang) (I have an E011 and UK65 models on it). When i select UK65 (Frsky) there's no noise. Probably because of the chips on the 4in1 module....I think there's different chip for Bayang vs Frsky. Buzzing noise not an issue i tnink....unless others didn't have it. I'm not worried.

I've upgraded to 2.3.9 and the internal 4in1 module to 1.3.1.9 (when you upgrade to 2.3.9 and go into your model settings, under the Internal Module, it tells you that it needs upgrade). So far so good. SD card issue gone.
https://github.com/pascallanger/DIY-...odule/releases

Originally Posted by robster303

I just checked. Buzzing noise is very faint and you have to put your ear to the loudspeaker. This noise only comes when i select my E011 (Bayang) (I have an E011 and UK65 models on it). When i select UK65 (Frsky) there's no noise. Probably because of the chips on the 4in1 module....I think there's different chip for Bayang vs Frsky. Buzzing noise not an issue i tnink....unless others didn't have it. I'm not worried.

Thanks! Ordered today from China. Must be a sample variation thing.

This seems like a good transmitter so far. Seems to have great features in small package. I never had the full sized ones, but i saw them in a shop and they were massive. Lets see how i go....its not like i'm flying for hours on end. Batteries only last few minutes whatever size quad.

What about the signal lost with timer alarm? That fixed too?

Is this better than the T8SG Plus V3?

Sent from my Pixel 4 XL using Tapatalk

Signal lost thing i believe it is although i haven't tested or use that. CurryKitten and myself were talking about that when i had the SD card contents listing issue - they are both related to DMA (Direct Memory Access) issue.
T8SG no idea.

Can this radio be configured to output a PPM signal to its JR-type external module?

Thanks,

Paul

Yes. Turn on External RF, then Mode to PPM instead of Multi.