For the first time since I tangled with that tree, I'm going out. To Stevenage, where there's a couple of good bike trails. I'm planning to start off by using my new battery pack, and run it till it's empty (3.2 volts per cell). If that goes well, I'm thinking of buying enough to make two more packs.
Hobbyking have an interesting discount system. When I was on their web site before, if I stayed on a page for a while, it would pop up an offer of a 7% or so discount. It doesn't seem to do that now, even though I've deleted the cookies.
But they have another discount, the "buddy discount". With that, I can get 13% off, which is nice. But when I tried to use it to order eight batteries, it wouldn't allow it; it seemed to top out at three. And it wouldn't let me buy three at the buddy price and five at the full price. It isn't worth putting in three separate orders, because of carriage. So it looks like I'll be paying the full price, although even their full price is really really low.