very quick question about Bg-E3 battery grip

[DStanic]

If the grip is left to "on" when the camera is turned off, will this drain the battery(s)? Is the on/off there just for the purpose of using the shutter/other buttons on the grip?

[Jon]

No. The On/Off switch on the grip just disables/enables the buttons on the grip. It has no effect on the power to the camera.

[Familiaphoto]

Jon said it all, the on/off switch just enables the bottons on the grip.