As most of us have learnt, battery chargers will charge more efficiently and batteries will last longer when they charge at a cooler temperature. I've been trying to think of a cost-effective heat-dissipating solution and I think I've found it in the form of the MiracleThaw(tm) defrosting plate!
It's just basically a large aluminium plate that acts as a heat-sink. I've seen purpose-built aluminium cooling pads (for notebooks), but they cost almost 80 bucks. Even though it's got two cooling fans, that's quite a bit to pay. I scored this thaw-thing for $9.90 off Y!Auctions!
It used to be everywhere where TV-Media "as-seen-on-TV!" products were sold. Now quite difficult to find, lah. But if you can find it, it's a great solution for your charger overheating problems. You will be able to thaw your frozen meat AND charge your batteries at the same time! How cool (pun!) is that?!