SkyGolf SkyCaddie SX400 Compatible Battery 3.8V 3750mAh

SkyGolf SkyCaddie SX400 — 3.8V Li-Polymer Replacement Battery (U744379PV)

This 3.8V 3750mAh Li-Polymer cell replaces part number U744379PV in the SkyGolf SkyCaddie SX400 handheld golf GPS. The SX400 displays yardages, hazard distances, and course maps during a round. Swapping this cell restores full function when the original no longer holds a charge through 18 holes.

• SkyCaddie SX400 fit: The SX400 uses a single-cell Li-Polymer pack at 3.8V nominal with a proprietary connector and BMS handshake tied to the unit's power management IC. This replacement matches that voltage rail and connector pinout exactly — the BMS communicates correctly on power-up without triggering a fault state.
• Bench tested on actual hardware: We cycled this cell through charge and discharge on the SX400 platform. The BMS accepted the cell, reported state-of-charge accurately across the charge curve, and did not trip the low-voltage cutoff prematurely during GPS-active discharge.
• First-power tip after fitting: After fitting this cell, power the SX400 on outdoors and let it acquire a satellite fix before heading out. The unit performs a cold start after any full power interruption — first fix can take 5–10 minutes outdoors. Subsequent warm starts are under a minute once almanac data is cached.

GPS accuracy reduced at low battery on the SX400

The SX400 scales back receiver sensitivity when cell voltage drops below a set threshold to reduce current draw and extend screen-on time. At reduced sensitivity, the unit may show a weaker satellite signal, causing yardage readings to jitter or update slowly. This is a firmware-level power decision, not a GPS hardware fault. Keeping the cell above 3.5V under load prevents the receiver from stepping down.

SX400 shuts off without warning before the low-battery indicator appears

After a battery swap, the SX400's fuel gauge needs a full charge-to-discharge cycle to recalibrate its voltage-to-capacity mapping. Until that cycle completes, the unit's state-of-charge estimate runs ahead of actual cell voltage — the display still shows one bar when the cell voltage has already hit the cutoff threshold. The fix is one full charge from flat to 100% without interruption. After that conditioning cycle, the low-battery warning and shutoff threshold realign correctly.