The Sram charger is probably bulkier than it needs to be, but if you carry 1 spare battery (which is sensible anyway on long trips) you could charge it on the go. Also depending on use, FD battery is likely to last longer, and you can swap it to the rear with the front staying on on of the rings in a 1x arrangement if you run out of battery.
Roughly about 4:
The Sram charger is probably bulkier than it needs to be, but if you carry 1 spare battery (which is sensible anyway on long trips) you could charge it on the go. Also depending on use, FD battery is likely to last longer, and you can swap it to the rear with the front staying on on of the rings in a 1x arrangement if you run out of battery.