Trimble Juno T41 Replacement Battery 3.7V 4000mAh

Trimble Juno T41 / Juno 5 / Slate — 3.7V Li-Polymer Replacement Battery (S11DG103A)

This 3.7V 4000mAh Li-Polymer battery replaces the OEM pack in the Trimble Juno T41, Juno 5, Juno T45, and Slate rugged handheld GPS receivers. These units run GNSS acquisition, sensor logging, and field data collection in environments where a wall outlet is hours away. Capacity is 4000mAh (14.8Wh) — same as the original S11DG103A specification.

• Juno T41, Juno 5, Juno T45, and Slate compatibility: All four models share the same battery bay geometry, 3.7V power rail, and BMS handshake protocol — the S11DG103A and its alternate part number S11GD103A are direct fits across the entire platform without firmware modification.
• Bench tested on actual hardware: We cycled this pack through GNSS cold-start acquisition, active Bluetooth data streaming, and screen-on logging simultaneously. The BMS held steady under combined load and cut in cleanly at the low-voltage threshold without a false trip.
• First field deployment prep: After installing, run a full battery calibration cycle through the Juno's system settings before heading out — the device maps voltage-to-state-of-charge during this cycle, and skipping it causes the battery indicator to report prematurely low levels during the first full logging session.

BMS lockout after the Juno sat unused in a carry case for months

Li-Polymer cells self-discharge slowly over storage — after several months unused, the pack voltage can drop below the BMS recovery threshold, typically around 2.5V per cell. At that point the BMS enters a protection state and blocks both charging and power-on attempts, so the device appears completely dead. Applying a compatible charger for 15–30 minutes at a low pre-charge rate is usually enough to bring the cell voltage back above the recovery threshold and re-enable normal charging. If the charger shows no activity after 30 minutes, check that the contact pins on the battery bay are clean and making firm contact.

Juno T41 shutting down during USB data transfer to a PC

USB data transfer activates the processor, storage controller, radio, and display simultaneously — this combined draw creates a brief current spike that an aged or partially depleted cell can't sustain without a voltage sag. When the cell voltage dips below the BMS cutoff threshold mid-transfer, the unit shuts off instantly to protect the cell. A replacement pack with intact cell capacity handles the spike cleanly because the internal resistance is low enough to deliver the current without the sag. Before the next transfer session, charge the battery to at least 3.9V per cell — visible as roughly 80–90% on the Juno's indicator — to give the BMS enough headroom.