DV Info Net - Save some misery when using an external battery

I want to share a lesson I learned the hard way when using an external battery to power my GoPro Hero3 Black although the problem can occur with any GoPro. I bought a battery that is often used to charge cell phones. I checked it out at home and it worked fine. I recorded 1080 video until I filled a 64 GB micro SD card which was six hours and forty five minutes. In subsequent use however the battery life was wildly variable. On some occasions it would shut down with an exhausted internal battery in much less time than that.

I did some serious testing to replicate the problem and found out what was happening. The particular battery I was using was designed to charge cell phones. It has a current detector that prevents overcharging cell phone batteries. When a cell phone battery is fully charged the current flow from the battery drops. When the current flow drops below a certain level, the battery shuts off. This prevents overcharging cell phone batteries. That's a bit of over caution because most cell phones protect themselves from overcharging. In any case, the battery charger manufacturer though this was a nice feature.

The problem is that the current level when this battery is used as an external battery on a GoPro is very close to the shut off current level on the battery. As a result, it would intermittantly shut off when used with the GoPro. Once off, a push button on the battery must be pushed to turn it on again.

The lesson learned is; if you use an external battery on a GoPro, make sure it doesn't have a low current shut down 'feature'. In this application, this isn't a feature; it's a big problem.