Metz 9745 Flash Replacement Battery 6V 4200mAh Ni-MH

Metz 9745 / 9747 / 9748 / 9783 — 6V 4200mAh Ni-MH Replacement Battery

This is a 6V 4200mAh Ni-MH replacement battery for Metz external flash units across the 9745, 9747, 9748, and 9783 series. These handle-mount flash systems draw significant burst current during capacitor recharge cycles, and the original Ni-MH cells degrade noticeably after repeated fast-recharge sessions. Capacity is rated at 25.2Wh.

• 9745 / 9747 / 9748 / 9783 compatibility: These four Metz flash units share the same handle-mount battery bay, connector pinout, and 6V operating rail. The BMS in each unit reads voltage and internal resistance — Ni-MH chemistry matches the discharge curve the flash controller expects during rapid recycling.
• Bench tested on actual hardware: We cycled this cell through repeated full-power flash sequences and monitored the BMS response at each recharge stage. Voltage held within spec across sustained high-demand bursts, and the controller did not trigger a premature low-voltage cutoff.
• Flash charger compatibility tip: Only use the OEM Metz handle charger or a Ni-MH charger that detects the negative delta-V termination signal — Ni-MH cells can overheat and lose capacity permanently if charged on a charger expecting Ni-Cd chemistry.

Flash recycling time increasing as Ni-MH cells age

Metz handle-mount flashes recharge the main capacitor at high current immediately after each shot. As Ni-MH cells age, internal resistance rises and the available current during that recharge window drops. The flash unit can still fire, but the recycling time stretches because the capacitor takes longer to reach full charge. A replacement cell with lower internal resistance restores the fast recycling the system was built around.

Flash output dropping inconsistently mid-shoot on a new cell

If output drops mid-shoot on a freshly installed cell, the most likely cause is the flash controller reading a voltage dip during the first few high-current recharge cycles and interpreting it as low battery. Ni-MH cells need one or two full charge-discharge cycles before internal resistance settles to its working minimum. Run one full charge in the OEM Metz charger, then complete a full discharge through normal shooting before the cell stabilises. After that break-in cycle, the voltage dip on recharge should stay above the controller's cutoff threshold — typically around 5.4V under load for this system.