> re: airline travel, > are there instructions anywhere on how to build a brick out of C's or D's > or whatever that would have many hours of capacity? I don't know if there are such instruction but it's not hard if you have an old DUO battery that's dead. Just open it up, pull the gut out but leave the connector in place. Add a pair of wires from the - and + terminal of the battery to an external battery case that has 10x rechargeable batteries. Finding a 10 battery case won't be easy, you're more likely to get a pair of 4 battery holders and one 2 battery holder.