Rob
I've just returned to the hobby, bought back in I got bought some Lipos from hobbyking. these are shorty packs not sure what fits your B4 if you use hobbyking use the UK warehouse tab (top left), these work out at £25 each, seem good i've not had any issues running out of power, reckon you get at least 20 mins out of a set. you'll need a lipo charger too i got the BMAX6 from hobbyking (£25-30) they do everything in $ when you shop with them just make sure its from the UK warehouse or you might get a VAT bill, i did on another order. paste the link into your browser.
i'm running a loss 22 2.0 with an orion 7.5T brushless motor and orion r10 pro speedo.
http://www.hobbyking.co.uk/hobbyking...rSearch=4600ma
Miles