We use BQ25703A charge for two cell, input voltage is 5V, but is can't boost charge for two cell, the full charger voltage is 8.6V. The register as below:
REG0x00 : 0x20e
REG0x02 : 0x9c0
REG0x04 : 0x2220
REG0x06 : 0x200
REG0x08 : 0xa00
REG0x0a : 0x0
REG0x0c : 0x1900
REG0x0e : 0x2800
REG0x20 : 0xac00
REG0x22 : 0x0
REG0x24 : 0x2800
REG0x26 : 0x1300
REG0x28 : 0x800
REG0x2a : 0x2500
REG0x2c : 0x4a4a
REG0x2e : 0x7840
REG0x2f : 0x1078
REG0x30 : 0x210
REG0x32 : 0x2b7
REG0x34 : 0x0
REG0x36 : 0x4a54
REG0x38 : 0x8120
REG0x3a : 0xa0ff