In reply to purplemonkeyelephant:
The power banks weren't a problem - put one inside your jacket rather than in your rucsac, so it stays warm, and keep it in your sleeping bag at night.
Also, my main navigation was my watch (a Suunto 9). I had all my tracks across the plateau pre-programmed. It doesn't use much power so I knew that one power bank was enough. If you have a phone, keep it on airplane mode unless you actually use it - it will use far less power.
On that note, one really good tip when it is really cold is to always put your gloves inside your jacket if you take them off - it keeps them warmer so any moisture inside them doesn't get cold or freeze. An hour of hot aches when you put them back on is just not worth it!
Post edited at 09:49