Yes, you can take fuel cells but spillable [lead acid] batteries are prohibited unless for a mobility device.
Alert: From January 1 2021, no loose or spare batteries will be allowed in passengers' checked luggage. This includes batteries in their original retail packaging. There will also be a limit of 20 loose or spare batteries of any type allowed in carry-on luggage, unless an airline has approved the carriage of more batteries. This is due to changes to the International Air Transport Association (IATA) Dangerous Goods Regulations.
Spillable [lead acid] batteries are not permitted onto aircraft unless for a mobility device and with the airline’s approval.
Fuel Cells are allowed in portable electronic devices [with two spares in carry-on] if they are marked "Approved for carriage in aircraft cabin only", if not, it MUST NOT be permitted on board the aircraft.
Not sure if you can take it? Contact your airline and check with them.
Batteries can overheat and catch fire.
You will be asked to relinquish all dangerous or prohibited items found in your carry-on luggage. If you refuse:
AvSec x-ray bags going onto aircraft to ensure there is nothing dangerous in them. If something comes up on the x-ray that needs checking, the bag will be opened, searched and any dangerous good or prohibited item will be removed, with a bag search notification form left within the bag.