About this replacement
Reichert PT100 Tonometer — 3.7V Li-ion Replacement Battery (13851-873)
This is a 3.7V 3400mAh (12.58Wh) Li-ion replacement battery for the Reichert PT100 portable applanation tonometer and EPG-1446. The PT100 measures intraocular pressure in clinical settings for glaucoma diagnosis and monitoring. This cell replaces OEM part number 13851-873 directly.
- PT100 and EPG-1446 compatibility: Both units share the same 3.7V single-cell architecture, connector pinout, and BMS handshake protocol — the same cell services either device without modification.
- Bench tested on actual hardware: We cycled this cell through the PT100's power-on self-test and intraocular pressure measurement sequence. The BMS accepted the cell, completed its verification pass, and held voltage within the device's operating window throughout the test load.
- First-use self-test protocol: After installing this cell, allow the PT100 to complete its full power-on self-test without interruption. Medical-grade BMS firmware runs a verification sequence at startup — cutting power mid-cycle flags a persistent battery fault that won't clear until the next clean reboot.
Why the PT100 rejects a new cell before clinical use
The PT100's BMS is calibrated to OEM cell chemistry and flags new third-party cells until one full charge-discharge cycle completes. This isn't a compatibility failure — it's the BMS learn cycle running as intended. On the first charge, the charge IC applies a conservative current limit, so the indicator may not reach 100% immediately. Run one complete charge-discharge cycle before using the device clinically, and the BMS will accept the cell's capacity curve.
Low battery alarm triggering immediately after a confirmed full charge
This happens when the BMS samples cell voltage before the resting open-circuit voltage stabilises — typically within the first few minutes after a charge completes. A new Li-ion cell needs surface charge to dissipate before resting voltage settles above the alarm threshold, which on the PT100 sits near 3.5V. Leave the device powered off for 10 minutes after charging, then power on. If the alarm does not clear, run a second full charge cycle to 4.2V and retest.