I moved the Battery/shipping discussion here.
Could it be an option for somebody in the EU to bring a battery or two in their carry on when flying to Australia? I am hoping to be flying from Germany to Australia at the end of the year.
At the start of the year I flew with a laptop battery in my carry on and the laptop in my checked bag.
I think you’ll have quite a few Australian friends if you do that. 
I chatted with my work colleague who was heading over to the UK on holidays if she could do that. When we made enquiries with the airline (Singapore Airlines if I recall) they would not permit spare lithium ion batteries be carried in hand luggage. If the battery was inside a working phone however…
I think you were given wrong advice. I’ve taken a look here: https://www.qatarairways.com/en/baggage/restricted.html
and here: https://www.singaporeair.com/en_UK/us/travel-info/baggage/baggage-restrictions/
I flew with Qatar airways when I carried on a spare laptop battery. A FP4 battery is about 15 Wh, so according to both of the above sources, unless I’m missing something, it should be ok to carry on up to 20 batteries Although I reckon I’d only try about 3 without any prior specific approval.
Bother. Regardless I don’t want to be dependent on others travelling from Europe just to get a battery!