About this replacement
Magellan RoadMate 5175TLM — 3.7V Li-ion Replacement Battery (SJM1300)
This is a 3.7V, 1300mAh Li-ion cell for the Magellan RoadMate 5175TLM and RoadMate 5175-LM portable GPS navigators. It replaces OEM part SJM1300 and fits directly into the original battery bay. If your unit shuts off mid-route or won't hold a charge through a full drive, this cell restores full power capacity.
- RoadMate 5175TLM and 5175-LM compatibility: Both model variants use the same battery bay dimensions and 3.7V single-cell architecture. The connector pinout and BMS communication line are identical across the two, so one cell covers both.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on a RoadMate 5175TLM unit. The BMS accepted the cell without fault flags, and the charge circuit reached a full 4.2V cutoff cleanly on the first cycle.
- Cold-start satellite acquisition after fitting: After any full power removal, the GPS module loses its ephemeris data and runs a cold start. Take the unit outdoors and power it on before driving — first satellite fix can take 5 to 10 minutes. Subsequent warm starts drop to under a minute.
GPS battery draining faster on active navigation than on standby
Active turn-by-turn navigation puts the GPS receiver, processor, and 5-inch display all under simultaneous load. The display alone at full brightness accounts for a significant share of draw. The GPS receiver stays locked and polling continuously during routing, unlike standby where it sleeps between fixes. Dimming the screen to mid-level is the single most effective way to extend charge duration on a drive.
RoadMate 5175TLM shutting off without low-battery warning
The battery indicator on this unit reads relative to a calibrated voltage curve stored in firmware. When a new or replacement cell is first installed, that calibration is mismatched — the unit can hit its internal voltage cutoff threshold before the visual warning has time to display. This is most common in the first two or three charge cycles. Run two full charge-to-discharge cycles and the indicator will track accurately against the new cell's actual discharge curve.