Home Forums Everything about everything else Wrong VBAT voltage – FIX

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  • #24543

    Seems like there has been a mixup at the manufacturing facility. The two resistors thats used to measure the VBAT are switched around on some boards. Looks like it’s one batch that suffers from error.
    You will only notice this when you actually decide to use the VBAT feature. You don’t have to worry if you don’t plan on using it.
    The bottom resistor should be 10K and the top resistor one should be 1K.
    If your voltage always reads max voltage you can try switching these around, or if the soldering is too small for you, I can help you out. Just send me an email.

    Sorry about the inconvenience.

    -Edit, Lauka is correct. The top one should be 1K

    Attachments:
    #24545
    2ma
    Participant

    Hi @David ! What will it cause ? I mean if the resistors are switch the Vbat will just not work or I’ll get a wrong voltage value ?

    #24546

    It will always show the battery as the max value, like 25V.

    #24547
    2ma
    Participant

    Ok thank you 🙂 Mine is good then 🙂

    #24624
    lauka
    Participant

    I can confirm that switching the resistors fixes it. Even after plugging in battery when they were wrong.

    But I think David’s comment was wrong, the top resistor in the picture is 1K and the bottom one is 10K.

    #24625
    Terje
    Moderator

    Totally stupid question I am sure, but… How does it work? Would replacing the 1K resistor with a 100K resistor yield the same result?

    #24626
    lauka
    Participant

    Terje, yes I think it should work as it is a 10:1 voltage divider. The solder pads are bit small for soldering a regular resistor there though. But it’s doable.

    I think only concern would be if the ADC sampling time would be too fast, so that the hold capacitor doesn’t have enough time to charge between different channels with the low current. But shouldn’t be an issue here.

    #24627
    papadkostas
    Participant

    For not experienced people here that have only soldering iron, I recommend using this technique to swap the resistors like shown on this video.

    #24699
    ryane67
    Participant

    Also confirm it fixes by swapping them around.. it was really weird seeing a constant 25v in cleanflight and on the osd. I thought at first I may have hurt the STM32 when I found it was receiving 2.8v on that pin but it appears to still be fully functional.

    #25127
    RC-Engineer
    Participant

    Hey folks, to be frank I do not trust myself desoldering such tiny parts. Rather new to this soldering fiddly bits;) And I’m not great at it..YET! I don’t want to chance frying my naze. You ( David W.) mentioned something of helping out in that case!? It shows the constant 25.5V with me.

    Thanks in advance =)

    #25150
    RC-Engineer
    Participant

    Oh I just happened to notice yesterday, that my newly installed beeper suddenly gave me the low voltage alarm sequence. So I land and it obviously shows the Constant 25V but reliably warns me at the correct threshold i set it to as per min. cell voltage. Can anyone confirm that behavior?

    #25202

    That is super strange! Wonder what’s going on. Will do some tests to see what’s happening.
    What level did you have your warning set at?

    #25206
    RC-Engineer
    Participant

    Hey David,

    refering to my email: no, you didnt miss this last post 😀 how could you. You are David, the master 😉

    Yeah thats what I thought too. I set my low voltage alarm to 3.8V for test purposes, and once my tri hit that lowV mark beeped the shit out of my guts. I wasn’t expecting it at aaaaall. Double checked if the beeper was telling me that. Beeping was gone after charging to 3.9x Volts and back after hitting 3.79 per cell. Flying 4s.

    #25507
    billyd
    Participant

    Ok I feel really dumb for asking this question but do I need to connect Vbat (next to the buzzer pads) on the naze frame of the mini to the main leads of the battery on the pdb frame to get voltage sensing in cleanflight?

    I think it’s pretty obvious I need to, since the only connection from the pdb to the naze is the 5v pads but I didn’t want to blow everything up. Cleanflight reads 0v when I plug in a battery.

    I was surprised David didn’t have that in the build video (he covered voltage telemetry question but not cleanflight voltage)… maybe it was too obvious? Anyway sometimes I think I might be better off without watching a build video because I become like a robot following the video verbatim instead of actually using my brain.

    So I will have to take my tri apart again for the 1000th time to solder the lead lol. I have actually flown it once (today) and flew till the battery died (it flew great) because I thought hey I’m protected by the low voltage buzzer in cleanflight (But I never checked cleanflight voltage readout until I drained the battery).

    #25692
    billyd
    Participant

    Ok the answer is yes you have to connect vbat to the main lipo pads in order for the naz to see the voltage. Of course.

    I also had the swapped resistors so I took it all apart and did both.

Viewing 15 posts - 1 through 15 (of 17 total)
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