I was playing with a set of Hopes for a few weeks and the charger never squeaked or squeeled when I was using it…in fact I've got a mate who has just opened upa bike shop and has a small number of Hope lights in stock (at good prices) – I'll ask him to try them all and see if any of them squeak.
I did smirk when I read your post suggesting it was some sort of cooling operation – as the charger is encased in a sealed unit, I'm not sure how it could be cooling as there is nowhere for the hot air to go or cold air to be drawn in…
However if you think spending that amount of cash on a light and charging system gives you that facility then carry on…I suspect there is something not quite right with it to allow you to hear the squeaking though rather than a rather clever cooling system.