I should also mention that I use the Nokia CA-100 USB to 2mm charger to provide the 5.7v power the BH-214 needs when powering off of my Bicycle power system or I am near a computer, it is smaller than carrying both a microUSB and 2mm mains/wall charger. Using a regular 1200mA Nokia 2mm phone charger caused the headset battery to really heat up and not take a full charge but the 300mA charger included with the BH-214 never caused problems.
I have not tested a Nokia phone charge with the new battery mod but the CA-100 works great.