You can replace FNB-72, 85 without reconstruction.
You can use Yaesu NC-72 Battery Charger for full charge.
Expand FT-817ND’s operating time, and high-power RF output.
inside battery use MAXELL Li-ion battery made in japan
1. To install the FNB817-L32 Li-Ion Battery Pack, first remove the battery compartment cover. 2. Lift out the FBA-28 battery holder, and disconnect the short cable connected to the FBA-28. 3. Before, you connect the short cable to the mating connector on the FNB817-L32, you had better to install the FNB-85 in the battery compartment. 4. Connect the short cable to the mating connector on the FNB817-L32 5. Replace the battery compartment cover. * If you have some difficulty to close battery compartment cover, remove rubber plates back side of the compartment cover