Nikon Retinomax I Compatible Battery 6V 2100mAh 24515

NiKon Retinomax I / II Series — 6V Ni-MH Replacement Battery (24515 / DDB30002)

This is a 6V, 2100mAh Ni-MH replacement battery for the NiKon Retinomax I, Retinomax II, Retinomax II K Plus, and Retinomax Auto-Refractor. These are handheld autorefractors used in clinical eye care to measure refractive error. The battery fits the original cell bay and communicates with the device's charge management circuit using the same connector and cell configuration as part numbers 24515 and DDB30002.

• Retinomax I through Auto-Refractor compatibility: All four models share the same 6V cell bay, connector pinout, and charge termination behaviour. The BMS expects a specific negative delta-V signal at full charge — the Ni-MH cell chemistry here produces that signal correctly, so the instrument stops charging without overrun.
• Bench tested on actual hardware: We cycled the pack through the Retinomax charge circuit and confirmed the delta-V cutoff triggered cleanly at full capacity. The BMS did not flag a charge fault, and the cell temperature rise during charge stayed within the instrument's thermal window.
• First-use calibration on the Retinomax: After installing the new pack, run a full calibration cycle from the instrument's system menu before clinical use. The Retinomax maps battery state during calibration, and skipping this step causes the low-battery warning to appear prematurely on the first examination session.

Retinomax shutting down mid-examination despite a charged indicator

The Retinomax draws a current spike each time the optical measurement module initialises — this happens at the start of every refraction cycle. An aged or partially depleted cell cannot sustain voltage through that spike, and the BMS trips the output to protect the circuit. The instrument reads as charged at rest because resting voltage is acceptable, but collapses under load. Replacing the pack and running the calibration cycle resets the instrument's load-voltage baseline so the low-battery threshold is accurate again.

Retinomax not recognising a new pack after the unit sat unused in its carry case

Ni-MH cells self-discharge over storage, and if the pack drops below approximately 4.8V the BMS enters a sleep state to prevent cell reversal. When a depleted pack is installed in the Retinomax, the instrument may show no battery indicator or refuse to power on at all. Connect the charger and leave it for at least 90 minutes without interruption — the charger applies a recovery trickle current that brings the pack above the BMS wake threshold. Once the BMS recovers, normal charge resumes and the instrument will power on.