As if keeping modern mobile phones charged wasn’t hard enough already, it’s about to get a whole lot more annoying.

For ‘security’, passengers flying to the US will now be required to demonstrate that their electrical devices turn on, and gadgets with flat batteries won’t be allowed on the plane. This is, apparently, so that al-Qaeda can’t replace the batteries with something even more explosive than lithium-ion cells.

However, I see a problem:

1. Modern electronic devices use lithium-ion cells.
2. Lithium-ion cells have a standard voltage, which is determined by their chemistry.
3. Higher voltages (multiples of the cell voltage) are obtained by connecting multiple cells in series.
4. The difference between a large lithium ion cell and a small one is that the bigger one lasts longer. (You also have to worry about the maximum discharge rate, but my back-of-the-envelope calculations suggest that’s not a problem.)

In other words, it seems quite possible to strip out most of a laptop battery, replace it with a solid block of C4, and fit enough small cells in the space that’s left to power it on long enough to get through security.

Now, I don’t know where to get a block of C4, and I’m certainly not interested in blowing up any aircraft, least of all one I’m flying on! However, I do know where to buy small lithium-ion cells, and if I can order them from China via eBay, terrorists can probably manage it too.