<p>Canon MIGHT be referring to using *rechargeable* Lions, and the very real dangers of multiple cells with different capacities. These types of incidents result in a cell being totally discharged, and having reverse current forced through it from the remaining cells in the pack.<br>
You can find out a lot more about this very real danger here:<br>
<a href="http://www.candlepowerforums.com/vb/forumdisplay.php?107-Smoke-and-Fire-Hot-Cells-and-Close-Calls-The-dangerous-side-of-batteries">http://www.candlepowerforums.com/vb/forumdisplay.php?107-Smoke-and-Fire-Hot-Cells-and-Close-Calls-The-dangerous-side-of-batteries</a></p>