About this replacement
Techkon SpectroDens / Spectrodens D-61 — 4.8V Ni-MH Replacement Battery (75119 504 521)
This is a 4.8V, 2000mAh Ni-MH replacement battery for the Techkon SpectroDens SpectroPlate and Spectrodens D-61 spectrophotometers. It matches OEM part number 75119 504 521 and fits directly into the instrument's battery compartment. The SpectroDens platform uses this cell pack for portable colour measurement in print quality control and dental applications.
- SpectroDens and D-61 compatibility: Both models share the same 4.8V four-cell Ni-MH configuration and battery footprint. The connector pinout and physical dimensions — 51 × 29 × 29mm — are identical across the SpectroDens SpectroPlate and D-61 variants, so one SKU covers both instruments without modification.
- Bench tested on actual hardware: We cycled this pack through the SpectroDens charge circuit and confirmed the BMS accepted the new cells without error flags. Current draw at sensor initialisation stayed within the pack's delivery threshold, and the instrument completed full measurement sequences without mid-session cutoff.
- Post-install calibration cycle: After fitting this battery, run a full calibration cycle through the instrument menu before field deployment. The SpectroDens maps battery state during calibration — skipping this step causes premature low-battery warnings to appear during your first measurement session, even with a fully charged pack.
BMS lockout after the SpectroDens sat unused in a carry case for months
Ni-MH cells self-discharge over time, and a pack left in storage for several months can drop below the BMS recovery threshold. When this happens, the instrument either refuses to power on or shows no charge response when placed on the dock. The fix is to apply a trickle charge externally using a compatible Ni-MH charger at 0.1C — for a 2000mAh pack, that means 200mA — until cell voltage climbs back above approximately 4.0V. Once the pack recovers to that level, the instrument's own charge circuit will take over normally.
SpectroDens shutting down mid-measurement during a logging session
This shutdown is not the same as a low-battery warning — it happens when voltage drops sharply under the sustained load of the sensor array during a continuous logging run. Aged or partially discharged Ni-MH cells show high internal resistance, and the resulting voltage sag crosses the instrument's undervoltage cutoff mid-sequence. A fresh pack at full charge resolves this; if the new battery still causes shutdowns, check that the instrument firmware is current, as some versions have an aggressive undervoltage threshold that a firmware update corrects. Confirm cell voltage is reading 4.8V nominal at rest before starting a logging session.