Sprint VIA820 Replacement Battery 3.7V 750mAh Li-ion

Sprint VIA820 — 3.7V Li-ion Replacement Battery

This is a 3.7V, 750mAh Li-ion cell for the Sprint VIA820 smartphone. It fits directly into the VIA820 battery bay and connects to the same charge IC and fuel gauge circuit as the original. Capacity is rated at 2.78Wh — use the figure from this listing, not third-party sources.

• VIA820 platform fit: The VIA820 uses a single-cell Li-ion pack with a 3.7V nominal rail. The connector pinout and BMS communication lines match the original charge IC handshake, so the phone recognises the new cell without any hardware modification.
• Bench tested on actual hardware: We ran this cell through full charge and discharge cycles on a VIA820 unit. The BMS accepted charge current normally, protection circuits triggered correctly at voltage floor, and no thermal flags were raised during the charge phase.
• Fuel gauge recalibration on first use: After fitting this cell, disable fast charging and run one complete discharge-to-charge cycle before normal use. This lets the fuel gauge IC map the new cell's discharge curve before drawing high current into an uncalibrated cell.

Why the VIA820 reports wrong battery percentage after a cell swap

The VIA820 uses a coulomb counter tied to the original cell's discharge profile. When a new cell goes in, that stored profile no longer matches the actual voltage-to-capacity curve of the replacement. The phone reads state-of-charge from a map it built around a degraded or different cell, so percentages can appear inflated or deflated. One full uninterrupted discharge cycle down to automatic shutdown, followed by a full charge, forces the fuel gauge IC to relearn the curve against the new cell.

Sudden shutdown at 20–30% on the replacement cell

This is a voltage cliff problem, not a capacity problem. Under modem transmit or screen-on load, the cell voltage drops faster than the fuel gauge predicts, crossing the BMS cutoff threshold while the display still shows charge remaining. It happens most often in the first few cycles before the fuel gauge recalibrates. Run two full discharge-charge cycles without interruption — if shutdowns persist past that, check resting cell voltage with a meter; it should sit at or above 3.7V after a full charge.