About this replacement
Mobistel Cynus E5 / E5 4G — 3.8V Li-ion Replacement Battery (E500615050011476)
This 3.8V, 1700mAh (6.46Wh) lithium-ion cell replaces the original battery in the Mobistel Cynus E5 and Cynus E5 4G smartphones. It matches the OEM part number E500615050011476 and fits the original battery bay without modification. It restores power to a phone that no longer holds a charge or shuts down unexpectedly.
- Cynus E5 and E5 4G fit: Both variants share the same battery footprint, connector pinout, and BMS handshake protocol. One cell covers both models with no adapter or wiring change needed.
- Bench tested on actual hardware: We cycled this cell through charge and discharge on the Cynus E5 platform. The BMS accepted the cell without error, and the charge IC held a stable taper current to full termination voltage.
- Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one complete discharge-charge cycle. This gives the fuel gauge IC time to map its coulomb counter against the new cell's discharge curve before high-current charging begins.
Sudden shutdown at 20–30% on the Cynus E5 after a battery swap
A new cell has a discharge curve the phone's fuel gauge IC has never seen before. The IC still references the old cell's voltage-to-capacity map, so it misreads remaining charge under load. When the modem fires a transmission burst or the screen peaks, the cell voltage drops sharply below what the IC predicted — the phone interprets this as a critical low and cuts power. One full discharge-charge cycle forces the coulomb counter to reset and relearn the new curve. After that cycle, shutdowns at 20–30% typically stop.
Cynus E5 not powering on after sitting in storage with a flat battery
Lithium-ion cells that discharge below approximately 2.5V per cell trigger a BMS lockout — a protection state that blocks current flow to prevent cell damage. A phone in this state shows no response: no charging indicator, no boot screen. Connect the phone to a wall charger rated at least 5V/1A and leave it undisturbed for 20–30 minutes. The BMS recovery circuit trickle-feeds current into the cell to bring voltage back above the lockout threshold, after which normal charging resumes.