Pentax 29518 Replacement Battery 7.4V 2000mAh Li-ion

Pentax 29518 / 38403 / 46607 / 52030 Series — 7.4V Li-ion 2000mAh Replacement Battery

This is a 7.4V, 2000mAh Li-ion replacement battery for Pentax survey and measurement instruments including models 29518, 38403, 46607, and 52030. It matches the original cell dimensions at 70.60 × 38.60 × 20.54mm and fits the stock battery compartment without modification. Voltage and capacity match the OEM specification exactly.

• Cross-model compatibility on this platform: These Pentax instrument models share the same battery bay geometry, contact pin layout, and 7.4V voltage rail — the BMS in each unit reads cell state over the same communication protocol, so one pack covers the full group.
• Bench tested on actual hardware: We cycled this pack under a simulated sensor-initialisation load profile. The BMS held regulation through repeated probe power-up spikes without triggering an overcurrent cutoff, and cell voltage recovered cleanly between draws.
• First-install calibration step: After fitting this pack, run a full calibration cycle through the instrument menu before field deployment. The instrument maps battery state during calibration — skipping this step causes premature low-battery warnings during the first measurement session, even with a fully charged pack.

BMS cutoff when a probe module initialises at power-up

When a Pentax survey instrument powers on with a probe or sensor attached, the module draws a short inrush current spike to initialise. An aged or deeply discharged pack can see its cell voltage sag below the BMS protection threshold during that spike, triggering an immediate cutoff. The instrument appears to restart or shut off instantly — the battery looks charged, but it cannot sustain the peak draw. Charge the pack fully to 8.4V before the next session and verify terminal voltage holds above 7.2V under load before connecting the probe.

Instrument shuts down mid-measurement during a sustained logging session

During continuous data logging, sensor modules draw steady current across the full session — longer than typical spot-check use. If cell capacity has faded or the pack was not fully charged, voltage drops under sustained load and the instrument's low-voltage cutout trips, ending the session and losing unsaved data. This is a different failure from probe-initialisation cutoff — it builds gradually over the session rather than happening at startup. Top the pack to 8.4V before any extended logging job and confirm the instrument's battery indicator reads full after the post-install calibration cycle.