Bacharach PCA-400 Replacement Battery 3.7V 5200mAh

Bacharach PCA-400 — 3.7V Li-ion Replacement Battery (0024-1664)

This is a 3.7V, 5200mAh Li-ion replacement for the Bacharach PCA-400 portable combustion analyzer. It slots into the same bay as the OEM pack and uses the same connector and BMS handshake. Technicians carrying the PCA-400 to boiler rooms, mechanical spaces, and job sites need a battery that holds up under sustained sensor load.

• PCA-400 fit confirmed: The PCA-400 runs a single-cell Li-ion architecture at 3.7V nominal. This pack matches that voltage rail, the physical footprint (66.80 × 36.65 × 19.00mm), and the OEM connector orientation — so the instrument's power management circuit recognises it without firmware complaints.
• Bench tested on actual hardware: We cycled this pack through full charge and discharge on the PCA-400 platform. The onboard BMS handled probe initialisation current spikes without tripping, and the cell sustained voltage under continuous sensor sampling without dropout.
• First-use calibration step: After installing this pack, run a full calibration cycle through the PCA-400 instrument menu before heading to site. The analyzer maps battery state during calibration — skipping it causes the low-battery indicator to trigger early on the first measurement session, even with a full charge.

BMS lockout after the PCA-400 sat unused in a carry case for months

Li-ion cells in idle instruments self-discharge slowly over weeks. If the PCA-400 is packed away between seasonal service contracts, the cell voltage can drop below the BMS protection threshold — typically around 2.5V — causing the pack to enter a locked state. At that point, the instrument won't power on and the charger shows no activity. To recover, connect the pack to a compatible Li-ion charger that supports a low-voltage wake or trickle pre-charge mode, hold it at a low charge rate until cell voltage climbs above 3.0V, then charge normally.

PCA-400 shutting down mid-measurement during a logging session

This is not the same as a dead battery — the instrument can show adequate charge on startup, then cut out while actively logging combustion data. The cause is voltage sag under sustained sensor load: the electrochemical sensors and heated probe draw continuous current, pulling cell voltage down enough to trip the BMS undervoltage cutoff before the indicated charge reaches zero. An aged or partially degraded cell sags faster because internal resistance rises as the cell wears. If this happens mid-session, charge the pack to full, re-run the calibration cycle, and check that cell voltage at load stays above 3.4V during startup.