About this replacement
COSMED Pony FX NTA2531 — 7.4V Li-ion Replacement Battery (A-410-750-002)
This is a 7.4V 2600mAh Li-ion battery for the COSMED Pony FX NTA2531 portable metabolic analyzer. It replaces OEM part number A-410-750-002. The Pony FX is a clinical-grade cardiopulmonary exercise testing device used in hospitals and sports medicine labs to measure VO₂, VCO₂, and respiratory parameters during patient diagnostics.
- Pony FX NTA2531 fit: The NTA2531 uses a 7.4V two-cell Li-ion pack with a multi-pin connector that carries both power and BMS communication signals. The replacement cell matches the OEM voltage rail and connector pinout so the device firmware can read charge state correctly.
- Bench tested on actual hardware: We ran this battery through full charge-discharge cycles and confirmed the BMS handshake completes without fault flags. The protection circuit held cutoff at the correct low-voltage threshold under simulated clinical load draw.
- Post-swap startup protocol: After installing this battery, allow the Pony FX to complete its full power-on self-test cycle without interruption. The device runs a BMS verification sequence at startup — cutting power mid-sequence logs a false battery fault that persists until the next clean reboot.
Device not completing boot sequence after battery swap
The Pony FX firmware expects a BMS that has completed at least one full charge-discharge cycle before it will pass the startup battery verification check. A brand-new cell fresh from packaging may have a state-of-charge the BMS reports as nominal, but the charge IC hasn't yet calibrated its capacity register. This causes the boot sequence to stall or throw a battery fault on first power-on. Run one complete charge cycle to 8.4V and allow the device to boot cleanly before scheduling clinical use.
Charge indicator not reaching 100% on the first charge cycle
On a new Li-ion cell, the Pony FX charge IC applies a conservative current limit and terminates early until the battery's internal resistance profile is established. This is a normal first-cycle behaviour — the charge register hasn't synchronized with the new cell's capacity baseline yet. The indicator will reach full on the second or third charge cycle once the BMS learn cycle completes. Do not interrupt the first charge; let it run to termination and then discharge the device under normal operating load before recharging.