Electric Folding - Series 2, S2 – Biria Bikes The BIRIA Electric Folding, Series 2, with upgraded battery, tires, pedals, and charger. Has the appearance of a normal folding bike with the Lithium ion battery hidden inside the … The BIRIA Electric Folding, Series 2, with upgraded battery, tires, pedals, and charger. Has the appearance of a normal folding bike with the Lithium ion battery hidden inside the …