Hello,
I wonder why no one is considering a pack of 6 x Ansmann NiMH Akku D Mono 10000 mAh ?

http://www.ansmann.de/cms/en/consumroot/batteries-battery-packs/rechargeable-batteries-nimh/mono-d/10000mah.html

I guess this should be enough for a night.

regards,
Matthias

I've used battery packs made of NiMH D-size cells with mixed results. My 40D wouldn't work reliably (and sometimes not at all) with NiMH cells, have no idea why. I think to a lesser extent I had reliability issues with other DSLRs too. I do use a pack with a Canon compact and have had no issues with that setup, and I think others have used NiMH packs with DSLRs too without trouble. So you may well be fine with them, but to me it was an unknown I did not want to deal with.

Other reasons for me to pick Li-Ion is better cold temperature performance and significantly lower self-discharge rate. This is not to discourage use of NiMH packs; mostly they should work just fine and probably do.