BG-E3 Battery Drain - Both concurrently, or 1 at a time?

Looking at getting a BG-E3 battery grip, but wanted to find out if I need to order more batteries (have 3). Does the battery grip drain one battery at a time, or does it drain both batteries concurrently? Thinking of my rotation scheme. Thanks!

Both batteries are used simultaneously.

dont think it operates the same as your normal AA battery where one drains out if plugged simultaneously together. I've just got a generic grip and it works great.

gofer wrote in post #5724431
Both batteries are used simultaneously.

Thanks! I guess I should visit SterlingTek again..

No doubt about it, both batteries are discharging at the same time. You will never find yourself with one discharged battery and one fresh one (unless you start that way).

Just to clarify the point, both batteries are discharging at the same time, but your camera will work with a single battery loaded in the grip, ie, it doesn,t necessarily need two batteries to be installed

bear in mind that 2 batteries gives you a much longer life, so it might just turn out that running 2, with one spare is all you need...when the 2 run out, slam in the 1, and charge the 2...will probably suffice.

i rarely have to worry about batteries on the 400 now, and the grip makes a big improvement to the handling.