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I have an old GoPro Hero 2 who's external USB plug has failed, and I have no way of powering it externally. I need to run this GoPro using an external wired power source (available over a 5v USB).

There are battery eliminators available for the Hero 3 (example) that replace the battery unit with a USB cable connecting directly to the device's leads.

Is this product nothing more than a glorified power cable inputting 5V? Or is there a voltage regulator and thermistor dummy circuit in there? Could I build my own or modify something like this to work with a GoPro Hero 2?

For reference, the battery of the GoPro Hero 2 and 3 are 3.7v.

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    \$\begingroup\$ Is the GoPro the only camera you've got and is that why you didn't post a photo of the problem? \$\endgroup\$ – Transistor Jul 7 '16 at 17:17
  • \$\begingroup\$ You could build your own or modify something, but I think it might be easier to replace the USB connector. \$\endgroup\$ – Mark Jul 7 '16 at 23:08
  • \$\begingroup\$ @transistor what part of the question could be improved with a photograph? There's a standard set of 3-pin Li-Ion leads on the GoPro Hero 2 (that normally take 3.7v) and I have 5v USB power available; I want to know if I can power the device with a relatively simple circuit between these leads and the source. I provided an example of what I am looking for, only that model fits a Hero 3. Is this Battery Eliminator just a set of wires to the battery leads, or does it need a voltage regulator and thermistor dummy circuit? I don't feel confident in my ability to replace the USB connector. \$\endgroup\$ – SkyNT Jul 8 '16 at 3:54
  • \$\begingroup\$ The photo would give us the ability to offer other suggestions (which may not answer the question directly but may get the camera going at little or no cost). "... that replace the battery unit with a USB cable connecting directly to the device's leads." This bit wasn't clear. What is the "device" and what are its "leads"? \$\endgroup\$ – Transistor Jul 8 '16 at 5:41
  • \$\begingroup\$ @transistor added picture. Exactly what the Switronix Battery Eliminator does for the Hero 3 model. Can I build my own? I am willing to solder directly onto the leads, as the camera is old and serves only this one purpose. It doesn't have to be pretty; it just has to work. Fixing the integrated USB connectors is not a long term solution for the type of environment in which the camera will be deployed (because the connector sticks out). The integrated USB connector on this particular unit has already failed once and was serviced, and now has failed again. \$\endgroup\$ – SkyNT Jul 8 '16 at 15:11
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According to Benlo.com:

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Figure 1. Hero 2 battery eliminator connection points.

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Figure 2. Hardwired Hero 3 battery eliminator.

Using a Battery Eliminator with the Hero 3 Camera

GoPro cameras can be run off a 4 volt power source which replaces the internal battery. The voltage must be no less than 3.75V and no greater than 4.2V. The power supply must be capable of supplying 0 to 1.1 A of current without deviating from the above range. The T-sense pin on the camera is not needed with a battery eliminator power supply.

You can't supply directly from USB 5 V supply. Some form of regulation will be required.

schematic

simulate this circuit – Schematic created using CircuitLab

Figure 3. Simple "constant" voltage dropper.

You could try the circuit of Figure 3 to power the camera. The theory of operation is that

  • each diode will drop 0.7 of a volt when even a few mA is drawn through them.
  • R1 draws the small current so the voltage across the resistor should be about 3.6 V.
  • Depending on your exact 5 V voltage from the USB port, the diodes and the camera this might just work. It won't cause any damage as it would be the same as a flat battery.
  • If it doesn't work then you could replace one or both diodes with Schottky diodes which have a lower forward voltage drop.

Procedure:

  • Connect up the components but not the camera.
  • Plug in to USB port and measure voltage across R1.
  • If voltage is about right then unplug USB, solder up and test.
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No, directly connecting 5V to a li-ion battery connection is a bad idea. Most battery eliminator circuits will regulate to a voltage within the battery range. Use a regulator with the usb power supply down to say 3.8 or 4 V.

Or replace the broken usb connector with a cable.

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