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I was wondering how waterproof wristbands are charging. I suppose is a common technique that all vendors are using. For example my wristband has two exposed leads as it seems below.

enter image description here

The charger has similar leads that fits to the wristband and a micro usb for current input. When i am trying to measure the voltage on the two exposed leads i am not getting anything, as expected because the device is waterproof, but these leads are charging the wristband.

Does anyone know how this charging method work?

How these leads are going "active" when the charger is attached?

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    \$\begingroup\$ Being waterproof doesn't stop the terminals from conducting electricity for battery charging. \$\endgroup\$ – Finbarr Oct 14 '19 at 15:06
  • \$\begingroup\$ They might have a voltage detection circuit on the inputs. The terminals are probably attached to a charging circuit. \$\endgroup\$ – Voltage Spike Oct 14 '19 at 15:07
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    \$\begingroup\$ It's unsurprising that you would not be able to externally measure anything, there is probably a diode if not an entire internal charging circuit between those contacts and the battery cell, so that something like shorting the contacts with car keys or loose change or whatever they might come into contact with does not drain or worse damage the cell. \$\endgroup\$ – Chris Stratton Oct 14 '19 at 15:12
  • \$\begingroup\$ It wouldn't surprise me if there were an internal reed switch that is only activated when the magnet holding the contacts together is present. \$\endgroup\$ – Dave Tweed Oct 14 '19 at 15:51
  • \$\begingroup\$ Also, if this is a model with the gps option Huawei likely knows where you are and where you've been. \$\endgroup\$ – Nedd Oct 14 '19 at 16:04
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Two PIN charging port, connected to charging cradle through clip.

They use magnetic holders to make contact with 2 pins and often a cradle needs to keep it on side or raised so the strap or cable forces do not separate the magnetic holders to permit contact with pads.

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Is it possible this is a health or exercise band? In which case these might be skin contact tabs that measure skin resistance. From your picture there also seems to be an optical input for possible blood flow/pulse rate detection, etc. If there is a usb connection is it possible this is the charging method, or there could be a wireless inductive charger anywhere under the plastic cover.

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  • \$\begingroup\$ No there are not skin contacts or any GSR sensor. They are for charging. \$\endgroup\$ – alexisicte Oct 15 '19 at 6:10

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