Anyone using a 3rd party battery for their 1D Mk III

[bigrob]

Thinking of getting a spare but wondered if anyone had good / bad experiences with 3rd party batteries.

 

[JohnStewart]

I bought one from 7dayshop.com, but it was dead on arrival. Sent it back for a refund. To be honest, I've taken over 2,000 shots in one day, and the battery still had over 40% life left, and I can't think of many situations when I would need a spare battery.