Oh well, If you have had a rough experience with lipos then you may want to try the ones widow twanky suggested earlier: http://www.alpha-crucis.com/en/batterie ... 22554.html
they weigh less than 20grams they are also tiny 3x2x1.5cm. and not very expensive for 7.2v 200mah batteries
but it is a seller from abroad and you may have to pay import tax and all that junk i got when I ordered the banebots from america.
thanks