Hello Sakis. I would recommend you buy the 7.4v. Lithium Polymer Battery from the Robot Store for a couple of reasons. For one thing, it is much cheaper: going for a price of only $21.00 when on the other hand the other battery from Active Robots comes down to almost $70-$80. In addition, the Robot Store's product has more voltage of 7.4 v. DC than that of the 7.2 volt battery, which is not too high to short circuit an EZ-Board, but has a healthy amount of power. So there you have it, the true winner is Robot Store's 7.4 v. Lithium Polymer battery. Glad to help.~RoboticsMaster

Hi RoboticsMster , and thanks for the help

I'am going to order my new battery .

Thanks again for your replay.

I would recommend this: http://www.ebay.com/itm/280541163795?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1497.l2649