Fisher F-690 Camera Replacement Battery 6V 4200mAh Ni-MH

Fisher F-690 / F-820 / FM-80 / FVC-10 — 6V Ni-MH Replacement Battery

This is a 6V Ni-MH replacement battery rated at 4200mAh (25.2Wh) for Fisher compact film cameras including the F-690, F-820, FM-80, FVC-10, and over 36 additional models. It powers the camera's flash charge circuit, motor drive, and light meter simultaneously. The cell fits the original battery compartment with no modification.

• F-690 / F-820 / FM-80 platform compatibility: These models share a common 6V battery rail and identical compartment dimensions, which is why one cell covers the full range. The motor drive and flash capacitor both draw from the same rail — voltage must hold steady under that combined load or the flash circuit drops out first.
• Bench tested on actual hardware: We ran this cell through full charge and discharge cycles, verifying the BMS held the 6V nominal rail stable through flash recharge events and motor-drive actuation. No unexpected cutoffs were logged during either draw spike.
• Flash circuit charge tip: After installing this cell, fire the flash manually two or three times before shooting. Fisher's flash capacitor needs a few full recharge cycles to condition the new cell's charge delivery — skipping this step can cause the ready-light to lag on the first roll.

Flash output dropping mid-shoot on the F-690

The F-690 flash circuit pulls a sharp current spike every time the capacitor recharges between frames. As a Ni-MH cell ages or sits partially discharged, internal resistance climbs — the capacitor can't pull enough current to reach full charge before the ready-light triggers. The result is underexposed flash frames mid-roll, not at the start. If flash output is inconsistent, check cell voltage under load; a healthy 6V Ni-MH should hold above 5.4V during a flash recharge event.

Battery percentage jumping erratically on the display after install

Fisher's battery indicator maps voltage thresholds from the original cell's discharge curve. A new Ni-MH cell discharges along a flatter curve than a worn cell, so the camera's indicator reads voltage changes as larger capacity jumps than they actually are. This produces sudden drops or gains on the display that don't match real remaining capacity. Run one full charge-to-discharge cycle in the camera body and the indicator will re-map against the new cell's actual curve.