Use a special cable - 4 cell split into 2 x 2 cell (sold in Chi Lok). connect two packs of 2 cell battery in series ( one pack + to B6 + terminal, this pack - to another pack +, then another pack - to B6 -). It is like charging a 4 cell pack but split into 2 x 2 cell pack.
Use a special cable - 4 cell split into 2 x 2 cell (sold in Chi Lok). connect two packs of 2 cell battery in series ( one pack + to B6 + terminal, this pack - to another pack +, then another pack - t ...