About this replacement
Motorola i870 / i450 Series — 3.7V Li-ion Replacement Battery (SNN5705)
This is a 3.7V, 1000mAh Li-ion cell built to replace the OEM battery in the Motorola i870 and compatible handsets. It fits the i870, i450, i415, and i215, among others. Physical dimensions are 57.74 × 35.50 × 7.43mm — measure your existing cell before ordering if you are unsure.
- i870 / i450 / i415 / i215 compatibility: These models share the same battery bay dimensions, 3.7V nominal rail, and connector pinout. The BMS handshake protocol is consistent across this family, so the same cell works without modification.
- Bench tested on actual hardware: We cycled this cell through full charge and discharge on the i870 platform. The BMS held cutoff correctly at the low-voltage threshold and accepted charge without tripping protection at standard current.
- Fuel gauge recalibration on first use: On first use after installation, run one complete discharge down to auto-off, then charge uninterrupted to 100%. This gives the fuel gauge IC a full voltage-curve reference against the new cell before the OS starts reporting percentages.
Sudden shutdown at 20–30% on the i870 after a cell swap
The i870's fuel gauge IC stores a discharge curve calibrated to the original cell's internal resistance profile. A new cell has a different impedance, so the IC misreads remaining voltage under load — particularly when the modem fires up during a call or data session. The phone interprets the brief voltage sag as a near-dead cell and shuts down, even though charge remains. One full discharge-to-cutoff cycle followed by an uninterrupted charge resets the coulomb counter and resolves this. After that cycle, shutdowns below 30% should stop.
Phone shows wrong battery percentage after replacement
When you swap cells, the fuel gauge IC still holds the old cell's learned capacity model. It maps voltage readings to percentages using that stale curve, so the display can jump, stall, or read 15% higher or lower than actual. This is not a fault in the new cell — it is the IC working from outdated data. Force a recalibration: drain the phone to automatic shutdown, then charge straight to 100% without interruption. The IC locks onto the new curve at that point and percentage reporting stabilises.