You either have two bad batteries or one bad charger.
Amazon sell the charger for £86 and a 36v battery 2.6AH for £123
My guess is a defective charger - there's an article about repairing the 3640 charger here...
https://galooph.com/blog/2015/11/13/repairing-a-bosch-al-3640-cv-charger/
Good Luck...
March 2017