After roughly 6 weeks since I received this Power 4 battery I was finally in a position to fly it this morning.
It performed well.
I needed to delay take-off a few minutes while I waited for some people to walk clear of my Area Of Operations so take off was at 16.6v. In the air having a 'normal' kind of flight (no hover test) for 12 minutes and 6 seconds landing at 14.7v. This in temperature of 3c. I wanted to fly it longer down to 14.4v but had to land because some people entered my Area Of Operation again. As a rough comparison I also flew my Gifi8050 in similar conditions where that one was in the air for 12 minutes and 35 seconds taking off at 16.7v and landing at 14.7v (people knocking around again)...so, roughly speaking, this new (to me) Power 4 battery seems to be performing the same as my Gifi8050
I admit that this wasn't an ideal test of this battery. I knew that I wouldn't be able to hover test it because people were coming and going and I had a mission on to take video of a certain landmark. Next time I fly it, then, I'll try to do it in a place where I can hover test it to 14.4v to see what sort of maximum time I can get out of it. But extrapolating up from what I did today I think it would easily come close to my Gifi, if not surpass it.
By the way, once I've processed the video I'll post a link to the pictures & video section. That'll likely be tomorrow.