About this replacement
Mobile Warming Men's Primer Shirt — 7.4V Li-Polymer Replacement Battery (MW74V22-SF)
This 7.4V, 2000mAh lithium-polymer battery replaces the original power pack in the Mobile Warming Men's Primer Shirt and several compatible Mobile Warming heated garments. It connects to the shirt's integrated heating elements and controller board using the same connector and voltage rail as the factory unit. Capacity is 2000mAh (14.8Wh) — identical to the OEM specification.
- Primer Shirt, Ion Shirt, Primer Pant, and Ion Pant compatibility: These garments share the same 7.4V two-cell Li-Polymer architecture, matching connector housing, and BMS handshake protocol — which is why one battery serves the full lineup without modification.
- Bench tested on actual hardware: We cycled this battery through all three heat settings on a Primer Shirt. The BMS held steady current delivery on low and medium. On high, the protection circuit flagged a brief inrush spike on startup but settled within two seconds — normal behaviour for this garment's heating element draw.
- First-use heat setting protocol: Run the shirt on the low or medium setting for the first 10 minutes before switching to maximum. The heating elements pull peak current at high, and a fresh cell benefits from a short warm-up period before full-load operation — this matters more with Li-Polymer than with cylindrical Li-ion cells.
Why the Primer Shirt stops reaching full heat on the highest setting
The shirt's controller reads battery voltage before switching to maximum output. If the pack voltage sags below roughly 7.0V under load, the controller won't sustain the high-heat element draw — it throttles back rather than risk a hard BMS cutoff. A worn or partially discharged original battery will fail this threshold first on high. A fresh 2000mAh pack at full charge sits above 8.3V open-circuit, giving the controller enough headroom to hold maximum heat through the bulk of a charge cycle.
Heating element cuts out mid-use and won't restart immediately
This is a BMS overcurrent trip, not a dead battery. Sustained maximum current draw — especially in very cold conditions where internal resistance rises — can push the protection circuit past its threshold, which latches the output off. The pack needs a short rest before the BMS resets and allows current flow again. To clear the trip, disconnect the battery from the garment, wait 30 seconds, then reconnect and restart on a lower heat setting. If the cutout repeats immediately on high, check the battery's resting voltage with a multimeter — it should read at least 7.4V before reconnecting.