Wahoo Tickr X suddenly inverts readings

Just sharing this bug here, as it’s kinda funny… Half way through my training session, the Tickr X decided to invert the readings, looks like 210 - HR… check it out… My heart rate goes up as I recover :smiley:

Would be great to fix, but in the meantime what’s the fastest way to reset it? I tried disconnecting the press-studs for 10 seconds and also disconnecting in the running SYSTM desktop app, but no change. Right at the end it seemed to fix itself, but by then the session HR recordings were useless.

Chdck the battery compartment for water intrusion. I had a pinched seal (o-ring) and i saw the same thing as sweat entered the compartment.

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Will do, cheers

Tiny bit of moisture in there, despite the cover and o-ring looking intact. Maybe that was it. Cheers.

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To reset, open the battery compartment, remove the battery and reverse polarity put the cover back on for 3 full seconds then, put it back the way it is supposed to be.

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As an electrical engineer, putting the battery in backwards gives me the heebie jeebies. But if that’s the design… will give it a go next time, thanks!


It’s from The Company support site for troubleshooting their HRMs. :man_shrugging:t3:


Putting in the battery ‘upside’ down applies no power but allows overcharged components to discharge and reset.


I am a professionally qualified electronic engineer, with nearly 25 years in my field.

Without asking to see the circuit schematics, I would like an explanation of how reversing the polarity

Batteries provide power if there is a closed circuit. If there is no circuit, nothing more will happen than just taking the battery out - without some other special circuit going on.

How are components being “overcharged”? That sounds like a tremendous design fault straight away.

Without some sort of reverse polarity protection on sensitive circuits (ADCs, at least), damage could occur. Capacitors should discharge (probably slowly) with just the battery removed.

Similar to @gwydion, I wince whenever I read this instruction and it goes against almost everything I’ve learned.


Interesting. R u and @gwydion saying that putting the battery in backwards could cause a problem with a unit like an HRM?

I’m saying that it is unclear to me why Wahoo tech support recommends this because I do not understand how that circuit works.

Ordinarily, applying reverse polarity to the input power could cause problems.

I was rather highlighting Sir @jmckenzieKOS text that was a bit hand-waving and rubbed me up the wrong way :grinning:


I’d suggest just reversing the rubbing polarity so it’s the right way :wink: :joy:

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I just add official link to that recommendation https://support.wahoofitness.com/hc/en-us/articles/115000359464-TICKR-Troubleshooting - see reset Tickr chapter.

Yes, I know the official line and I’m not doubting that it works.

My engineering question (which will likely remain open until I start working for Wahoo :grinning: ) is why it works when reverse polarity is usually very bad.

It definitely isn’t “applies no power and allows overcharged components to discharge and reset”.

It doesn’t matter - I’m just academically interested.


I’m no electrical engineer, but I once barely passed a class in it on my way to being a mechanical engineer! Anyway, with the coin style battery, wouldn’t flipping it upside down more or less ground it out since both contacts would be negative to negative instead of negative to positive? That’s the only thing my non electrical brain can think of….

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I’m not quite sure how you are thinking.

The load circuit has no concept of positive and negative. The “ground” is provided only by the battery. Demonstrably this cannot be ground but can only be one side of the battery.

Batteries only provide a difference in potential - positive and negative are naming conventions only. Current flow (by convention) will still occur from higher potential to lower potential, if a closed circuit exists.

Reversing the polarity to the load circuit just means that the higher potential is now connected to parts of the circuit that are not designed* to receive higher potential (electrolytic capacitors, for example, do not behave very well when reverse biased. Small transistors may fail completely when reverse biased meaning the cannot behave correctly when correctly biased).

*unless the circuit is designed for this but I can’t imagine what this really looks like if the only reason to reverse the polarity is to initiate some sort of device “reset”.


This thread has evolved into my favourite discussion on here :wink: The electronic design mystery continues… shrouded in a haze of blue smoke…

But I think I have the answer… Putting the battery in backwards doesn’t reverse the current direction, due to the position of the battery contacts. Putting it in backwards will cause both positive and ground terminals to make contact with the larger positive surface of the coin battery, while the negative surface is isolated. That connection would short circuit positive and ground on the PCB and potentially (pun intended) allow capacitors to discharge and should not generate too much heat if they are small caps.

Mystery… solved?

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So @jmckenzieKOS’ comment way earlier was the right answer all along!

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I’ll admit I have not taken my unit apart to observe how the connections are made. This does sound like the solution, then.

Edit: now I’ve had a look. You’re absolutely right @gwydion (da iawn!).

I apologize to all in the thread for my technically correct but ultimately aimless wittering :grinning:

I’ll report to some suitable flogging station …