What is Reddit's opinion of OCOOPA Hand Warmers Rechargeable, 1 Pack 5200mAh Electric Portable Pocket Warmer/Power Bank, Heat Therapy Great for Outdoor Sports, Hunting, Golf, Camping, Warm Gifts for Women, Men, Blue?

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I bought this one last year and it’s a life saver! It has 3 settings, gets warm very fast, and lasts hours. It even doubles as a phone charger. I can honestly say this little gadget has improved my quality of life. Game changer! This is the one I have, but they have other models as well:

OCOOPA Hand Warmers Rechargeable, 5200mAh Electric Portable Pocket Hand Warmer/Power Bank, Great for Outdoor Sports, Hunting, Golf, Camping, Warm Gifts for Women, Men https://www.amazon.com/dp/B07H3MKM8K/ref=cm_sw_r_cp_api_glt_fabc_GH7QCWNHBV5RVHY5KNHV

What about this?

Woke up early this morning and trekked to the top of a tower to shoot the sunrise. It was about 20 degrees out with a light steady breeze.

I was warm enough but my camera (Sony NEX 5R) just couldn’t stay on. I had fully charged batteries and a hand warmer in my pocket. I’d get 2-3 shots and then the camera would die. I’d swap in a warm battery and get another 2-3 shots if I was lucky before it would die again. Repeating this process eventually froze my hands.

I ended up taking some cell phone pictures and packing up during golden hour, which was frustrating.

Any tips for shooting in cold weather would be greatly appreciated.

The handwarmer I found doubles as a battery backup and lasts a pretty long time.

Edit: found this article which is pretty handy https://www.outsideonline.com/2282021/how-photograph-wildlife-winter