About this replacement
Typhoon MyGuide 4200 / 4228 Series — 3.7V Li-Polymer Replacement Battery (P675045N)
This 3.7V, 1450mAh lithium-polymer cell replaces the original P675045N battery in the Typhoon MyGuide 4200, MyGuide 4228, and MyGuide 4228WE portable GPS navigators. It matches the original cell's dimensions at 49.62 × 43.35 × 5.37mm, so it seats correctly in the battery bay without modification. Voltage and capacity figures are taken from the product data, not estimated.
- MyGuide 4200, 4228, and 4228WE compatibility: All three units share the same battery bay dimensions, connector pinout, and 3.7V supply rail. The P675045N part number covers the full series, and the OEM cross-references 50000215 and PND4220 confirm the same physical and electrical specification across variants.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the MyGuide platform and confirmed the BMS accepted the cell without fault flags. Charge acceptance was normal from both the cradle and USB input, and the protection circuit responded correctly at low-voltage cutoff.
- Cold-start behaviour after fitting: After fitting a new cell, power the navigator on outdoors with a clear view of the sky. The unit performs a full cold start after any power interruption — first satellite acquisition takes 5 to 10 minutes. Subsequent warm starts are under a minute once almanac data is cached.
GPS accuracy reduced at low battery on the MyGuide 4200
When the cell voltage drops toward its lower threshold, some GPS units reduce RF receiver sensitivity to cut current draw. On the MyGuide 4200, this can cause position drift or a loss of fix in areas with moderate signal. The navigator may still show a location on screen, but it is interpolating rather than tracking live satellites. Keeping the cell above 3.5V during active navigation avoids this mode entirely.
MyGuide 4200 shutting off without low-battery warning
As a lithium-polymer cell ages, its voltage sags under the current draw of the GPS receiver and backlit display together. The navigator's low-battery indicator is calibrated against a cell with healthy internal resistance — a degraded cell can sit at a displayed "medium" charge and then drop below the cutoff threshold almost instantly under load. The result is an abrupt shutdown with no warning screen. Fitting a fresh cell with lower internal resistance restores the normal warning sequence, and the unit will display the low-battery alert at the correct voltage before shutdown.