I have bought rc helicopter recently. I seem to be swelling up the Li po batteries. I have already swelled up three battery packs. One of my friends told me that it could because I was not letting Li po batteries to cool down just after using them and before charging. I even tried this but got no success. So, can tell me how to use Li po batteries properly? Also can someone tell me what causes Li po batteries to swell up? I would really appreciate early response. Thanks.