VG-D 70 Pics here.

Started Mar 14, 2005 | Discussions thread
Mark Roberts Contributing Member • Posts: 628
Battery life - Horses mouth

I think you guys have it figured out OK already, but I'll add some more to it.

The grip allows use of two batterys as well as an external power source. All three sources are connected together using diodes. Think of a diode as a one-way valve. The power source with the highest voltage will be connected to the camera contacts, and the other two will be essentiall disconnected. As one power source drops in voltage, the mix may change, so that the highest voltage is always applied.

So, if you have two charged battery packs installed, as the charge drops on one pack, the current will start to be drawn from the other, until it's voltage drops down below the first. Both battery packs will effectively discharge at the same rate, effectively half as fast as they would have normally.

If you use an external AC adapter with the grip, assuming the input voltage is higher than that of the battery packs, the battery packs will not be drained at all... all power will come from the external source.

Some real world details... the diodes used to connect the power sources to the camera are not perfect 'valves'. The voltage applied to the camera will be about 0.3V less than that of the battery. This means that the camera's battery monitor will start to show reduced battery charge a little earlier than if the battery were directly connected to the camera. This means that you won't get exactly twice the battery life, but very close to it.

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Canon EOS 5D Mark III
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