bobdabiulder

The car adapters are more efficient. Heat wont be a concern. I'd be more concerned with the 9v battery dying, they have low capacity ):

Is this the same as http://www.ebay.com/itm/121834376546 ?

Excellent work! I wish you luck in the competition, as a judge, you have my vote!

Nice! Any stats on it?

As long as the metals are different.

Thanks for the idea! Personally, making enough of these to do that would be a drain, but if you do that, please send pictures!

Although I've done it before, I was soldering onto a LiPo battery pack's charging circuitry. It was one of the small, rectangular pouch types from an RC helicopter.