Jet-black heart rate monitor disconnect with Bluetooth

Hi Zwift,

I purchased a jet-black heart rate monitor in November from your store and it has been working fine without any issues until the 20th of December.

When it disconnects it will not reconnect, it just drops off and the sporadically tries to reconnect without any success. I took the HRM off on the last ride and it was at times showing a heart rate, interesting as I’m not wearing, before disconnecting again.

I presumed it was a battery issue as I do 3+ hour rides on Zwift and thought I’d drained it, but checking the store it says the battery should last 20 months. Anyway, it has a new Duracell battery and it’s the same, last about 30 minutes and then completely drops.

I’m connecting directly to my laptop Bluetooth, my turbo is connected all the time without any issues, so it is only the HRM that is experiencing issues.

Any help is appreciated.

Kind Regards


Duracell batteries have the Bitrex coating to discourage children from eating them. This is a problem for many devices, so when troubleshooting coin cell battery issues I would choose a high quality uncoated battery such as Panasonic. Many device manufacturers (eg, Apple, Stages) say not to use coated batteries. With some effort the coating can be removed with alcohol.

If the battery is not the problem, I would troubleshoot by pairing it to something else. In Zwift you can switch to pairing via the Companion app to see if that’s more stable. That would use the Bluetooth hardware in your phone and bridge it to Zwift via WiFi. Using an ANT+ USB dongle (in the laptop) with an extension cable may also work more reliably. Even the cheap ones like Coospo work well. The extension cable is often necessary due to the limited range of ANT+.

A few trainers (including some JetBlack, Zwift, and Elite products) can bridge the HRM by pairing it to the trainer. If your trainer supports that, it’s another thing to try.

I use one of these straight into the laptop for my Garmin heart rate monitor

Fitcent ANT+ Dongle for Zwift…

I tried with the companion app and it was the same behaviour. The original battery was not Duracell and was experiencing the same issues. But, I’ll grab one of the other branded batteries I have for my next test.

I don’t have any ANT+ stuff anymore, I found that it was very unreliable and had loads of drops whilst riding, hence why I moved over to bluetooth, which has been perfectly fine for years until recently and only with this new HRM. I’ll have dig around, but I think it has all been lost in the house move earlier this year…

Ok, I tried with an ANT+ dongle and Panasonic battery and an energiser battery, the same dongle recommended below and I have the same issue, after about 25 mins it just does.

This time I tried turning the HRM the other way around to see if there would be any effect, what happened was the HRM triggered spurious data back for about 10 minutes and then went completely off again.

I believe there is a design fault with the HRM as I did a little inspection and there is moisture inside the battery cavity, so whatever IP rating it is this HRM is not good enough for long rides with me as I do get a little sweaty.

Never had these issues with the ANT + Garmin HRM and that one still continues to work as expected, just wanted to be all Bluetooth.

I’ll have to contact Zwift and see what they say…

Sounds like you should return the HRM and try another one. Garmin HRM-DUAL will do Bluetooth and I haven’t had any moisture issues with it over several years. Currently using a Coospo HW706 optical arm band but that’s more about convenience and comfort. The Garmin still works fine.

Did you found any working solution? I have the same problem with the same JebBlack HRM.

I contacted Zwift and they gave me a straight refund, no messing.

Before the refund, I did put some silicone sealant on the back of it and it did fix it. So it is the seal that isn’t up to the job.

Hope this helps

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