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Casio PRT-2GP Smartwatch Replacement Battery 3.7V 320mAh

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From $23.99 USD $29.99
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Fits Casio PRT-2GP smartwatch, replaces OEM part MR11-2286.
3.7V and 320mAh lithium-polymer cell powers display, sensors, and wireless connectivity on this GPS watch.
Connector type is proprietary magnetic pogo pins; align contacts flush with charging dock contacts before seating.
We bench-tested this cell on the PRT-2GP platform — BMS initialized cleanly, fuel gauge calibrated after full charge cycle.
After fitting this cell, place the watch on its magnetic charger immediately and charge to 100% before first use — the fuel gauge IC cannot calibrate without a full charge from near-zero after a swap.
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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

320mAh

Casio PRT-2GP — 3.7V Li-Polymer Replacement Battery (MR11-2286)

This 3.7V, 320mAh lithium-polymer cell replaces the original battery in the Casio PRT-2GP smartwatch. It powers the display, heart rate sensor, GPS, and BLE connectivity. Fit it when the original cell no longer holds a charge or the watch shuts down unexpectedly.

  • PRT-2GP platform fit: The PRT-2GP uses a 3.7V Li-Polymer cell with a specific connector orientation and BMS handshake tied to the fuel gauge IC. This cell matches the OEM voltage rail and physical footprint at 32.96 × 28.00 × 4.92mm — no trimming or adapter needed.
  • Bench tested on actual hardware: We ran this cell through a full charge cycle on the PRT-2GP platform. The BMS accepted the cell without a low-voltage lockout error, and the fuel gauge IC registered charge state correctly after a complete charge from near-zero.
  • Post-swap charging on the PRT-2GP: Place the watch on its magnetic charger immediately after fitting this cell and charge it to 100% before use. The fuel gauge IC on this platform cannot set an accurate reference point without a full charge cycle starting from near-zero — skipping this step causes the display to read 0% or fluctuate wildly.

Why the PRT-2GP battery drains in one day instead of several

The PRT-2GP stacks continuous heart rate monitoring, GPS polling, and BLE syncing on a 320mAh cell. If all three run simultaneously with always-on display enabled, current draw rises sharply and the cell depletes far faster than the rated multi-day estimate. Check your sensor settings — GPS set to continuous rather than interval mode is the single biggest draw. Switching GPS to smart/interval mode and disabling always-on display brings current draw back to the expected range for this cell capacity.

Watch not pairing to phone after battery swap

Removing the battery clears the active BLE session stored in volatile memory — the watch and phone no longer share a valid pairing key. The watch is not faulty; the connection simply needs to be re-established from scratch. On your phone, go to Bluetooth settings, forget the PRT-2GP, then re-pair through the Casio companion app as if setting it up for the first time. The new pairing completes in under a minute once both devices are discoverable.

Compatible Models

PRT-2GP

Replaces Part Numbers

MR11-2286

Technical Specifications

Voltage3.7V
Amp Hours320mAh
Capacity320mAh
Rate1.18Wh
Net Weight7.4g /0.26 oz
Gross Weight32g /1.13 oz
Approximate Weight32g /1.13 oz
Dimension 32.96 x 28.00 x 4.92mm

Product Highlights

  • Brand: Casio
  • 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 PRT-2GP shows 0% battery immediately after I swapped the cell — is it dead already?

No — the fuel gauge IC lost its reference point when the old cell was removed. It cannot report an accurate state of charge until it completes one full cycle from near-zero. Place the watch straight onto its magnetic charger and let it charge uninterrupted to 100%. After that first full charge, the percentage reading will track correctly.

Heart rate sensor seems to be killing the new battery much faster than the GPS does — is this normal?

Continuous optical HR monitoring runs the sensor LED and photodetector constantly, which draws more current on a fresh cell than on a degraded one with higher internal resistance masking the true load. This effect is most noticeable in the first week as the new cell settles. If drain remains excessive after seven days, check whether the HR mode is set to continuous rather than auto or on-demand — switching to auto reduces sensor current significantly.

The magnetic charger is sitting on the watch but the charging icon never appears after fitting the new battery — what's wrong?

The charge contacts on the case back can shift slightly during reassembly, breaking the magnetic alignment. Remove the watch from the charger, reseat it slowly until you feel the magnet snap to centre, then check for the charging icon within five seconds. If it still does not appear, inspect the contact pads on the watch for any adhesive residue from the battery replacement and clean them with a dry cotton swab before reseating.

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