MetroPCS C88 Replacement Battery 3.7V 800mAh Li3708T42P3h

MetroPCS C88 / C78 / C70 / E520 — 3.7V Li-ion Replacement Battery (Li3708T42P3h553447)

This is a 3.7V, 800mAh Li-ion cell built to fit the MetroPCS C88, C78, C70, and E520 smartphones. It replaces OEM part Li3708T42P3h553447, the original battery used across this family of budget touchscreen handsets. Swap it in when the original cell no longer holds a charge or causes unexpected shutdowns.

• C88 / C78 / C70 / E520 platform compatibility: These four models share the same battery bay dimensions, connector pin-out, and BMS handshake protocol, which is why a single cell covers all of them. The 54.29 × 33.71 × 4.43mm footprint matches the cavity on each device without modification.
• Bench tested on actual hardware: We ran this cell through charge and discharge cycles on the C88 platform. The BMS accepted the charge IC handshake on first connection, and protection cutoffs triggered correctly at both the low-voltage floor and high-voltage ceiling.
• Fuel gauge recalibration after install: On first use, disable fast charging and run one full discharge-to-charge cycle. This lets the fuel gauge IC map its coulomb counter against the new cell's actual discharge curve before high-current charging pushes into an uncalibrated state.

Sudden shutdown at 20–30% on the C88 after a cell swap

The C88's fuel gauge IC stores a discharge curve from the old cell in non-volatile memory. When a new cell arrives with a different internal resistance, the gauge miscalculates remaining capacity and tells the OS the phone has 25% left when the cell voltage has already dropped below the modem's minimum rail. The modem and screen together pull enough current to collapse the voltage past the BMS cutoff, and the phone shuts down hard. One full discharge cycle — down to the auto-off point, then a full charge — forces the coulomb counter to relearn the actual voltage cliff on the replacement cell.

Phone not powering on after the replacement cell sat in storage

Li-ion cells self-discharge during storage, and if this one dropped below approximately 2.5V per cell, the BMS entered lockout mode to prevent damage from deep discharge. Plugging in the charger may show nothing for the first few minutes — that is normal. The charge IC trickle-charges the cell at a low current rate until voltage climbs back above the BMS reactivation threshold, typically around 2.9–3.0V, at which point normal charging resumes and the phone will power on.