@CobaltVR, I looked into this and it seems like disconnecting the USB from the battery side is the safest option to turn off the adapter. It does have a "standby mode" in the sense that it uses the SteamVR proximity sensor idle and thus there is less transmission occuring since there is no video transmission - this does indeed lower the draw from the battery but is not a true "standby mode" in the more traditional sense.
I've flagged all of this feedback to the product team as it's all quite valid.
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