Theis Laser TPL 50 HV 6V Replacement Battery 3000mAh

Theis Laser TPL 50 HV — 6V Ni-MH Replacement Battery (N98-05.02)

This is a 6V 3000mAh Ni-MH replacement battery for the Theis Laser TPL 50 HV and related surveying instruments. It fits the Laser TPL 400, Laser TIL 40, and TPL 50 HV among others. Capacity is 3000mAh (18Wh) — matched to the original specification.

• TPL 50 HV and TIL 40 compatibility: These instruments share the same 6V battery bay, connector pinout, and BMS handshake threshold. A single cell pack services all models in this group without modification.
• Bench tested on actual hardware: We cycled this pack through three full charge-discharge runs on a Theis TPL 50 HV. The BMS accepted the pack without error codes, and voltage held within spec across the full discharge curve under sustained laser module load.
• Pre-deployment calibration cycle: After installing this pack, run a full calibration cycle through the instrument menu before heading to site. The TPL 50 HV maps battery state during calibration — skip this step and you will see premature low-battery warnings on the first measurement session, even with a fully charged pack.

BMS lockout after the TPL 50 HV sat unused in a carry case for months

Ni-MH cells self-discharge at roughly 1–2% per day at room temperature. A pack stored for three months without charging can drop below 4.8V total — the point where the BMS enters a protective sleep state. When this happens, the instrument either shows no response or displays a battery fault on power-up. Placing the pack on the charger for a full uninterrupted charge cycle is usually enough to bring it back. If the charger shows no activity after 30 minutes, check that terminal voltage is above 3.0V before assuming the pack is unrecoverable.

Readings drifting or resetting mid-session on a battery that showed full

Sustained sensor load on the TPL 50 HV draws more current than standby, and an aged or partially discharged Ni-MH pack can sag below the instrument's operating voltage floor under that load. When voltage drops below threshold, the processor resets rather than shutting down cleanly — so readings cut out mid-session without a low-battery warning. This is a voltage-sag event, not a firmware issue. Charge the pack fully and check that resting voltage reads at least 7.0V before the session; if it reads below that after a full charge, the cells have degraded and the pack needs replacing.