I started flying my Unicorn wing with 2000 mah Engerizer packs I made. I would get decent flights with a Speed 400. I switched to
Hecell 1800 mah 4/5 A and CBP 1800 4/5 A and the difference was spectacular, not only in spped but in flight time. The better higher discharge rate batteries are about $2.50 each, the inferior 2100 Energizer are about $2.75 to $3.00
Try this web site for high discharge batteries, look at the CBP 1800 and recently I built a CBP 2100 A size, it is heavier at 11.4 oz but the perfromance is worth it
http://www.unipros.com/cbpsite/custo...sion_id=123388