How to extend battery life in cold weather

I was recently trying to shoot video with my A55 in sub freezing temps. I was waiting for some action to occur while shooting the Sandhill Crane migration, but almost every time I went to start the video, the battery was dead from the cold.

I had three batteries with me, but due to swapping the batteries so often I missed the critical events - flocks of hundreds of large birds taking off - which happens with no warning.

I was thinking about rubber banding the hand warmers that you use in gloves to the camera to try and keep it warmer.  Does anyone have other suggestions?

My A700 did much better. I would last at least 20-30 minutes, but the A55 was dying in just a few minutes - and one of the batteries is fairly new.

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Shawn