About this replacement
Rotronic HygroPalm HP31 / HP32 / HP6 / HP7 — 3.7V Li-ion Replacement Battery (1ICP10/34/50)
This 3.7V 1800mAh Li-ion cell replaces part number 1ICP10/34/50 in the Rotronic HygroPalm HP31, HP32, HP6, and HP7 portable hygrometers. These handheld instruments measure humidity and temperature in laboratory, environmental, and industrial field applications. Physical dimensions are 53.00 × 33.70 × 10.30 mm — confirm these against your existing cell before fitting.
- HP31, HP32, HP6, HP7 platform fit: All four models share the same battery bay geometry, voltage rail, and BMS handshake protocol tied to the 1ICP10/34/50 cell specification. One cell covers the entire HygroPalm series listed.
- Bench tested on actual hardware: We cycled this cell through probe initialisation and sustained sensor logging. The BMS handled the current spike at probe power-up without triggering a protection cutoff, and voltage held steady under continuous measurement load.
- Post-install calibration step: After fitting this cell, run a full calibration cycle through the HP31 instrument menu before field deployment. The instrument maps battery state during calibration — skipping this step causes premature low-battery warnings to appear on your first measurement session even with a full charge.
BMS lockout after the HygroPalm sat unused in a carry case for months
Li-ion cells self-discharge during storage. If the HygroPalm sat long enough, the cell voltage can drop below the BMS recovery threshold — typically around 2.5V — and the protection circuit latches off. The instrument will show no response at power-on even when connected to a charger. To recover the pack, connect it to the OEM charger and leave it for at least 30 minutes before attempting to power on; most BMS circuits re-initialise once the cell climbs back above 2.9V. If the charger shows no charge activity after 30 minutes, the cell has likely gone below the recovery floor and replacement is the correct next step.
HP31 shuts down mid-measurement during USB data transfer to PC
USB data transfer adds a second current draw on top of the active sensor and display load. On a partially depleted cell, the combined draw can pull the terminal voltage below the BMS cutoff threshold even though the battery indicator still showed partial charge at power-on. This is a voltage-sag failure, not a capacity failure — the cell still holds charge but cannot sustain the combined load. To confirm, check the cell voltage under load with a multimeter: a healthy cell under this combined draw should stay above 3.5V. If voltage dips below 3.4V, the cell needs replacement.