About this replacement
Trimble Juno SA/SB/SC/SD Series — 3.7V Li-Polymer Replacement Battery (66450-00)
This 3.7V 2400mAh Li-Polymer battery replaces the OEM pack in the Trimble Juno SA, SB, SC, and SD handheld GPS receivers. These are rugged field data collectors used in surveying, mapping, and GIS work. Voltage and cell format match the original spec exactly — no adapter or modification needed.
- Juno SA/SB/SC/SD platform fit: All four Juno variants share the same battery bay dimensions, connector pinout, and BMS communication protocol. One pack covers the full series because Trimble kept the power architecture consistent across these models.
- Bench tested on actual hardware: We ran this pack through charge and discharge cycles on a Juno SD unit. The BMS handshake completed on first install, state-of-charge reporting was stable, and the protection circuit tripped correctly at the low-voltage cutoff threshold.
- Field deployment prep: After swapping the pack, run a full GPS acquisition and data-sync cycle before heading into the field. The Juno recalibrates its battery state indicator during active use — skipping this step often causes the low-battery warning to trigger early on the first full session.
BMS lockout after the Juno sat unused in a carry case for months
Li-Polymer cells that sit discharged long enough drop below the BMS recovery threshold — typically around 2.5V per cell. When this happens, the protection circuit locks out charging and the device shows nothing when plugged in. A standard charger won't break through because the BMS blocks current below that floor. Connect the Juno to its OEM cradle charger and hold it on charge for 20–30 minutes before attempting to power on — the charger's trickle stage can recover packs sitting just above the hard cutoff floor.
GPS receiver powers on but shuts off during USB data transfer to PC
USB data transfer pulls current from both the CPU and the USB controller simultaneously — on a degraded or partially charged pack, this combined load causes a voltage dropout that the BMS reads as an unsafe condition and cuts power. This isn't a firmware fault; it's the protection circuit doing exactly what it should when cell voltage sags under load. Charge the pack to at least 3.9V before starting any transfer session. If the shutdown repeats on a fully charged new pack, check the USB cable — a resistive cable increases draw and can tip the same threshold.