I did my dual battery mod by now as well...used the multistar 5200lihv charged by the turnigy charger to 17,4V. When I am charging my DJI battery to the max (battery powered on and than connected to the charger to get it to the max), the DJI battery goes only up to 17,1V....sooooooo...when I am connecting the multistar to the Dji battery, the DJI thinks it shall be charged again....as the voltage difference is still too big.
My question: Has anyone figured out a way to charge the DJI battery to 17,4V as well, so that both batteries start with the same max. voltage ? Is that a charger issue of the DJI charger or does the "intelligent" battery charger electronic in the DJI battery do not allow more than 17,1V ?