I pieced together the parts for a Force eTap mullet 
. The parts weren’t cheap, but somehow paying $80 for a battery isn’t sitting well with me when there are aftermarket ones on Amazon for 1/4 of the price. Has anyone tried aftermarket batteries? Is it a bad idea? I figure at the price it’s easy enough to carry a backup.
If they are of the same spec then they are the same. SRAM just buys batteries from some manufacturer and pays them to stamp SRAM on them.