ERA MDA I Compatible Battery 3.7V 1700mAh 35H10008-80

ERA MDA I — 3.7V Li-Polymer Replacement Battery (35H10008-80)

This is a 3.7V, 1700mAh lithium-polymer battery replacing OEM part 35H10008-80 in the HTC T-Mobile MDA I smartphone. It slots into the original battery bay and connects via the factory contact points. Capacity matches the original 6.29Wh rating.

• MDA I platform fit: The MDA I uses a fixed 3.7V single-cell Li-Polymer architecture with a direct contact connector — no latch or keyed tab. This cell matches that contact layout and the BMS voltage window the device expects at startup.
• Bench tested on actual hardware: We cycled this cell through the MDA I charge IC and confirmed BMS handshake on first insertion. The cell accepted a full charge without the device flagging a battery error or refusing to boot.
• Fuel gauge recalibration on first use: After fitting this cell, disable fast charging if available and run one complete discharge-charge cycle before daily use. The fuel gauge IC on the MDA I calibrates against the discharge curve it records on that first full cycle — skipping this leaves the percentage counter reading from stale data mapped to the old cell.

Why the MDA I reports wrong battery percentage after a cell swap

The MDA I uses a coulomb-counting fuel gauge IC that builds its percentage model from accumulated charge and discharge data. That data is tied to the old cell's internal resistance and discharge curve. When a new cell goes in, the IC is still reading against the old model, so the percentage shown can be off by 10–20 points in either direction. One full discharge to auto-off, followed by an uninterrupted charge to 100%, resets the reference curve. After that cycle, percentage readouts stabilise.

Sudden shutdown at 20–30% remaining on the MDA I

This happens when the cell voltage drops sharply under load — typically when the modem transmits or the backlight spikes current draw. The BMS cuts power the moment cell voltage hits its lower protection threshold, even if the fuel gauge still shows charge remaining. On a new cell, this usually points to an uncalibrated gauge rather than a faulty cell. Run the recalibration cycle described above; if shutdowns continue after that, check that the contact pins are seating flat — a high-resistance connection causes voltage sag that trips the BMS before the true cutoff of 3.0V per cell.