Originally Posted by neilm

I get a faint whistle from mine but nothing worrying!

If its loud I'd send it back as it could suggest a faulty cell or charger

Originally Posted by neilm

As long as it's still ticking you're OK!

I think I'd ring the supplier for advice.

Originally Posted by neilm

I did contact the supplier and got the same reply- the 13200mAh is rated at 5V. I disagree with this as a blunt statement and asked for clarification, but have had no further response.

It may be that the pack can only deliver its optimium performance at 5V- beyond this there will be more of a heating effect so the available power will be used in heat generation. I find the whole thing a little disingenuous- the pack is being sold as an extended battery for laptops and netbooks, with the capability of charging 5V devices over USB if needed. One might expect the rating to be consistent with the target devices.

As you say, this is still a great product, and I use mine frequently, but some mention of its limitations in the literature would be welcomed.