Just looking in the HV10 manual which you can download now at the canon site.
Very poor 'typical' recording times- supplied BP-310 45min
and optional BP-315 85min
So you have a HD cam in one pocket and a wedge of small batteries in the other!

Can you provide the link for the manual please?

Here is the requested manual link:
http://www.usa.canon.com/consumer/controller?act=DownloadDetailAct&fcategoryid=326&modelid=14059

" Very poor 'typical' recording times- supplied BP-310 45min
and optional BP-315 85min So you have a HD cam in one pocket and a wedge of small batteries in the other! " -

On the other hand, I just bought several aftermarket batteries online for $16.00 apiece!! I'd rather use small lightweight batteries for what I shoot ( on the fly climbing videos ) than have heavier batteries that throw off the balance of the cam.

is this where you got it?
http://www.bestbatt.com/Canon_BP_310_Camcorder_Battery_p/bbbp310.htm

Yes it is.

At bestbatt.com, they have both the BP-310 (standard with camera) and the double capacity BP-315 for the same $16 price. Does anyone have experience with the larger BP-315 battery? Does it throw off the balance of the camera at all or is it still slim and light enough that it wouldn't be a problem? Thanks for any help.

Is it possible to use a more powerful external battery pack, perhaps strapped to a belt, and use that hooked into the DC power socket?

Peter, the BP-315 is twice the width of the BP-310, so it sticks out a little, but it's very light weight so this is mostly cosmetic to me. It doesn't change how I hold the camcorder at all.