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Cisco CP-7921 Replacement Battery 3.7V 1200mAh 74-4957-01

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Fits Cisco CP-7921, CP-7921G, and CP-7921G Unified handsets; replaces OEM part 74-4957-01 and 74-4957-01 Rev. C1.
3.7V, 1200mAh Li-Polymer cell delivers 4.44Wh to sustain talk and standby cycles on this enterprise VoIP cordless handset.
Connector slides into the battery slot on the handset back panel with a single friction latch; no screws required.
We bench-tested this cell across three full charge cycles on a Cisco base station; BMS accepted the voltage handshake without error codes.
After installing, place the handset in the base for a full 16-hour charge before first use to reach rated capacity.
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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

1200mAh

Cisco CP-7921G Unified — 3.7V Li-Polymer Replacement Battery (74-4957-01)

This is a 3.7V, 1200mAh Li-Polymer battery for the Cisco CP-7921, CP-7921G, and CP-7921G Unified wireless IP handsets. It slots into the rear battery compartment and restores full wireless operation when the original cell can no longer hold a charge. OEM part numbers covered: 74-4957-01, 74-4957-01 Rev. C1, and 74-4958-01.

  • CP-7921 series compatibility: The CP-7921, CP-7921G, and CP-7921G Unified share the same battery bay dimensions, connector pinout, and 3.7V supply rail — all three accept this cell without modification.
  • Bench tested on actual hardware: We ran this battery through charge and discharge cycles on a CP-7921G unit. The BMS accepted charge from the Cisco base station without triggering a fault condition, and voltage under RF transmit load stayed within the handset's operating window.
  • First charge on the CP-7921G base station: Place the handset in the charging cradle immediately after fitting this battery and leave it for a full charge cycle before using it. Li-Polymer cells shipped in partial-charge storage state need one complete charge before the battery gauge calibrates correctly on this handset.

Talk time shorter than expected after fitting a new CP-7921 battery

A new Li-Polymer cell arrives partially discharged after storage. The CP-7921G's onboard fuel gauge reads this partial state and may underestimate remaining capacity for the first few cycles. Run two or three full charge-and-discharge cycles through the base station before judging actual capacity. After that, the gauge recalibrates and reported capacity stabilises at the rated 1200mAh.

CP-7921G loses DECT pairing after battery replacement

Removing the battery completely cuts power to the handset's volatile memory, which can clear the stored DECT pairing link on some firmware versions. When the handset powers back on with no base association, it sits idle and will not connect calls. Re-register the handset to the Cisco Unified Communications Manager following the standard DECT re-pairing procedure in your site's phone administration console. Confirm registration by checking the handset displays a signal icon and extension number at idle.

Compatible Models

CP-7921 CP-7921G CP-7921G Unified

Replaces Part Numbers

74-4957-01 74-4957-01 Rev. C1 74-4958-01

Technical Specifications

Voltage3.7V
Amp Hours1200mAh
Capacity1200mAh
Rate4.44Wh
Net Weight37.5g /1.32 oz
Gross Weight73g /2.58 oz
Approximate Weight73g /2.58 oz
Dimension 83.90 x 52.70 x 7.80 mm

Product Highlights

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

Frequently Asked Questions

My CP-7921G base station shows a charging error light after I fitted the new battery — is the battery faulty?

Usually not. A Li-Polymer cell shipped from storage can sit below the voltage threshold the Cisco base station expects before it starts a standard charge cycle. Place the handset in the cradle and leave it undisturbed for at least 30 minutes — the base will trickle-charge the cell until it crosses the acceptance threshold and then switch to normal charging. If the error light clears within that window, the battery is fine.

The CP-7921G handset is fully drained by morning even though I left it in the base overnight — why?

This is a seating issue, not a battery fault. If the handset is not fully seated in the cradle, the charging contacts don't make a reliable connection and the handset runs on battery all night instead of charging. Remove the handset, check the cradle contacts for dust or debris, reseat it firmly until you feel it click, and confirm the charging indicator light activates on the handset display.

Call quality drops and the CP-7921G starts breaking up when I move away from the access point — did the battery swap cause this?

Yes, this can happen if the battery voltage sags under RF transmit load. A cell that has not yet completed its first full charge cycle delivers lower sustained voltage, which causes the transmit circuit to under-power and reduces effective range. Charge the handset to 100% in the base station before making calls. If range is still reduced after three full charge cycles, check that the replacement battery voltage reads at least 3.6V under load with a multimeter at the battery contacts.

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