I have a heart rate monitor that uses a proprietary charging cable - that I have misplaced.

The charging area looks like this:

enter image description here

Is it possible to use an existing micro-usb cable and hack it to make this charge?

  • \$\begingroup\$ Contact the supplier. \$\endgroup\$
    – Andy aka
    Commented Apr 4, 2020 at 13:44
  • \$\begingroup\$ Is it possible? Almost certainly. Is it easy for the average hacker? Probably not. \$\endgroup\$ Commented Apr 4, 2020 at 13:47
  • \$\begingroup\$ @Andyaka I have one ordered, My question still stands. \$\endgroup\$
    – Keith
    Commented Apr 4, 2020 at 13:55
  • \$\begingroup\$ Where exactly is the charging inlet?? \$\endgroup\$ Commented Apr 4, 2020 at 14:29
  • 1
    \$\begingroup\$ Based on the FCC internal pictures it should be easy enough to connect 5v power and ground. Based on the pictures we can't tell which is which. An educated guess would be that the small pin would be 5v and the clip point ground. But we don't know if the device ended of the cable is 5v or lower. I can't make out the ICs on the pcb. \$\endgroup\$
    – Passerby
    Commented Apr 4, 2020 at 19:42

1 Answer 1


To be able to do this job, you need to know the following:

  • Voltage required by the device: you need to stick to the exact rating.

  • Current required by the device: to choose a charger that can at least supply that amount of current.

  • Polarity of charging terminal: so you don't mix the positive and negative and damage the device.

  • Have or be able to get a very similar terminal in shape to make a secure connection.

To know this information, you can either find it on the device, user manual of the device or just Google it for that specific model.

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    \$\begingroup\$ And need to know if the device requires a chip/logic/pull-up/down in the charger in order to validate the charger/cable as authentic. \$\endgroup\$
    – old_timer
    Commented Apr 4, 2020 at 17:22
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    \$\begingroup\$ It's a 2 pin connection used with any usb port on a commodity fitness tracker. Its not going to have authentication. \$\endgroup\$
    – Passerby
    Commented Apr 4, 2020 at 19:43
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    \$\begingroup\$ Thanks @TheRockSays. I'll have a peek at the manual when I get home. \$\endgroup\$
    – Keith
    Commented Apr 4, 2020 at 22:02

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