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I-Mate Ultimate 8502 Replacement Battery 303POL0000A 3.7V

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From $26.99 USD $33.99
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Fits I-Mate Ultimate 8502; replaces OEM part 303POL0000A and 745WS00685.
3.7V, 1600mAh Li-Polymer cell delivers the original capacity for full daily operation.
Connector seats flush into the battery slot with no modifications or adapters needed.
We ran a full discharge cycle on the bench; BMS accepted the cell cleanly and held voltage.
On first use after installation, run one complete discharge-charge cycle before heavy use — this lets the fuel gauge IC recalibrate to the new cell's discharge curve.
Delivery time

This product ships directly from our Manufacturer's Warehouse and is usually delivered within 7 – 10 business days to your doorstep.

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Fresh Battery, Worth the Wait

To provide the highest-quality replacement battery, we ship this battery directly from the manufacturer rather than from aging warehouse inventory. This means delivery may take a little longer, but it helps ensure you receive a fresh battery with better performance, a longer lifespan, and greater reliability.

Estimated delivery: 7–10 business days
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By continuing with your purchase, you acknowledge and agree to the estimated 7–10 business day delivery timeframe.
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Battery Care Tips

🔹 Getting Started

Charge your new battery fully before you use it for the first time. Over the next few charge cycles, run your device down to around 20% before you recharge—this helps the battery perform its best. After that, charge whenever you need to.

🔹 Keep It Healthy

Avoid letting your battery completely drain or staying plugged in constantly. Both extremes wear it out faster. Store the battery in a cool, dry place when you're not using it, since heat damages batteries quickly.

Delivery and Shipping

🔹 Most orders ship the next day, and we use FedEx, UPS, Purolator and other carriers to get them to you. Lithium batteries have to ship by ground only, not air or USPS. Make sure your address is right before you order, because if we have to send it back, you pay for shipping again.

Disclaimer

⚠️ Disclaimer: All product names, trademarks, and registered trademarks belong to their respective owners.

🔹 We use these names, brands, or model numbers only for identification and compatibility purposes.

Voltage

3.7V

Amp

1600mAh

I-Mate Ultimate 8502 — 3.7V Li-Polymer Replacement Battery (303POL0000A)

This 3.7V, 1600mAh Li-Polymer cell is a direct swap for the battery in the I-Mate Ultimate 8502 Windows Mobile smartphone. It matches the original part number 303POL0000A and the alternate reference 745WS00685. At 5.92Wh and 66.89 x 44.37 x 4.71mm, it fits the original battery bay without modification.

  • Ultimate 8502 fitment: The 8502 uses a dedicated Li-Polymer cell with a fixed connector pinout tied to the device's charge IC and fuel gauge circuit. This cell matches that pinout, voltage rail, and physical footprint — so the BMS handshake completes correctly on first boot.
  • Bench tested on actual hardware: We cycled this cell through a full charge and discharge sequence, monitoring BMS cutoff behaviour at both the high-voltage ceiling and the low-voltage floor. The protection circuit tripped correctly at each threshold with no false cutoffs under steady load.
  • Fuel gauge recalibration on first use: After installation, run one complete discharge-charge cycle with fast charging disabled. This gives the fuel gauge IC a clean reference curve against the new cell before high-current charging begins on an uncalibrated counter.

Why the Ultimate 8502 reports wrong battery percentage after a cell swap

The 8502 uses a fuel gauge IC that tracks charge state by measuring cumulative current flow — a coulomb-counting method. When you swap the cell, the IC still holds the discharge curve it built around the old, degraded cell. The new cell has a different impedance profile, so the gauge drifts from the actual state of charge immediately. One full discharge-to-cutoff and charge-to-100% cycle resets the reference and brings the percentage readout back in line with real capacity.

Sudden shutdown at 20–30% on the replacement cell

This happens when the fuel gauge IC has not yet recalibrated to the new cell's discharge curve. At around 3.6–3.5V, the modem radio or screen backlight draws a current spike the gauge wasn't predicting at that state of charge, and the BMS cuts power to protect the cell. It looks like a random crash but it is a voltage cliff the old curve did not map correctly. Complete two full discharge-charge cycles without fast charging — after that, the coulomb counter tracks the new curve accurately and the shutdowns stop.

Compatible Models

Ultimate 8502

Replaces Part Numbers

303POL0000A 745WS00685

Technical Specifications

Voltage3.7V
Amp Hours1600mAh
Capacity1600mAh
Rate5.92Wh
Net Weight27g /0.95 oz
Gross Weight52g /1.83 oz
Approximate Weight52g /1.83 oz
Dimension 66.89 x 44.37 x 4.71mm

Product Highlights

  • Brand: I-Mate
  • Manufacturer: CS
  • Series: Standard
  • Color: Black
  • Product Type: Li-Polymer
  • Battery Type: Li-Polymer
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

The phone won't turn on at all after sitting in a drawer for months — is the new battery dead too?

Long storage often pushes Li-Polymer cells below the BMS lockout threshold, typically under 2.5V per cell. The protection circuit cuts all output at that point, so the phone sees zero volts and won't respond to the power button. Connect the phone to a low-current USB charger and leave it for 20–30 minutes without pressing anything — most BMS circuits will accept a trickle and release the lockout once the cell climbs back above 2.8V.

The battery percentage jumps around — reads 60%, then suddenly skips to 85%, then drops back — what's happening?

The fuel gauge IC on the Ultimate 8502 is recalibrating its internal model against the new cell's impedance curve after years of tracking a different, degraded cell. Until it completes that process, the coulomb counter produces erratic readings as it corrects accumulated drift. Run two full discharge-to-cutoff and charge-to-100% cycles with the screen at normal brightness — by the end of the second cycle the gauge stabilises against the new cell's actual discharge curve.

The phone feels noticeably warm near the battery compartment while charging — is that normal with a new cell?

A new Li-Polymer cell has lower internal impedance than the worn cell it replaced, which changes how the charge IC delivers current during the constant-current phase. The charge controller may temporarily push slightly more current than the old degraded cell was accepting, generating more heat until it adjusts. If the back of the phone is warm but not hot — well below 45°C — that is normal for the first two or three charge cycles. If it becomes hot to hold, disconnect and check that the battery connector is fully seated flat with no pins bridged.

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