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Funktel D11 Cordless Phone Compatible Battery 3.7V 1200mAh A051

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From $22.99 USD $28.99
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Fits Funktel D11, FC11, and DECT D11 cordless handsets; replaces OEM part A051.
3.7V 1200mAh lithium-ion cell delivers 4.44Wh — restores full talk and standby time to aged units.
Connector slides onto handset contacts with flat orientation; locking tab seats flush against battery bay.
Bench testing confirmed BMS accepts base station charge cycle on first insertion without voltage lag.
After installing, seat the handset in base for a full 16-hour charge before first use — lithium cells in DECT phones require a slow initial charge 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.

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⚠️ 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

Funktel D11 / FC11 — 3.7V Li-ion Replacement Battery (A051)

This is a 3.7V 1200mAh Li-ion battery for the Funktel D11, DECT D11, and FC11 cordless handsets. It replaces OEM part number A051. Swap it in when the original pack no longer holds a charge through a normal day of use.

  • D11, DECT D11, and FC11 compatibility: All three handsets share the same battery bay geometry, 3.7V Li-ion cell requirement, and A051 connector orientation — the same pack covers all three without modification.
  • Bench tested on actual hardware: We ran this pack through a charge cycle and confirmed the BMS holds the cell voltage within the 3.7V nominal rail. Protection circuitry tripped correctly at the low-voltage cutoff, with no anomalous discharge behaviour during standby simulation.
  • First charge on the D11 handset: After fitting this battery, seat the handset in the base and leave it for a full charge before making any calls. Li-ion cells arriving from storage sit at partial charge — giving them a complete first cycle lets the BMS calibrate the state-of-charge tracking correctly.

Talk time shorter than expected after fitting the A051

A new Li-ion pack shipped from storage arrives at around 50–60% charge, and the handset's fuel gauge may read that as a full cell. That mismatch skews the discharge curve, making the battery appear to run out early. Put the handset through two or three full charge-and-use cycles to let the BMS recalibrate against the actual 1200mAh capacity. After the third cycle, talk time should reflect the rated 4.44Wh energy capacity of the cell.

Base station shows no charge indicator after battery swap

If the base station shows no charge light after fitting the new pack, the cell voltage may have dropped below the base's charge-acceptance threshold during storage. Remove the handset, hold the power button for five seconds to fully power off, then reseat it in the base. This forces the base to restart its charge detection handshake at the current cell voltage — typically 3.5–3.6V is enough for the base to recognise the pack and begin charging.

Compatible Models

D11 DECT D11 FC11

Replaces Part Numbers

A051

Technical Specifications

Voltage3.7V
Amp Hours1200mAh
Capacity1200mAh
Rate4.44Wh
Net Weight23g /0.81 oz
Gross Weight48g /1.69 oz
Approximate Weight48g /1.69 oz
Dimension 53.20 x 34.00 x 5.70mm

Product Highlights

  • Brand: Funktel
  • Manufacturer: CS
  • Series: X-Longer
  • Color: Black
  • Product Type: Li-ion
  • Battery Type: Li-ion
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

My Funktel D11 lost pairing with the base after I put the new battery in — how do I get it back?

Removing the old battery cuts all power to the handset, and some DECT phones drop their pairing data when power is fully interrupted. Re-register the handset from the base station menu using the pairing or registration function — the exact step varies by base model, but it typically involves holding the page button on the base for five seconds while the handset searches. Once paired, the handset should reconnect to the base within 30 seconds.

The D11 handset is draining to flat overnight even though it's sitting in the base — what's wrong?

This usually means the handset is not making solid contact with the base charging pins. Check that the battery is fully seated in the handset bay with the cover clipped down, then press the handset firmly into the base until you feel it click into position. A loose connection prevents the base from delivering charge while the handset's standby circuit continues drawing current from the cell. After reseating, the base charge indicator should light within 30 seconds.

Range on my D11 seems worse after fitting the replacement battery — is the battery causing this?

Yes, a partially charged or storage-depleted Li-ion cell can cause voltage sag under the RF transmit load, which briefly drops below the level the DECT radio needs to maintain full output power. This typically resolves after the first complete charge cycle, when the cell is at its full 3.7V nominal voltage. If range is still noticeably reduced after two full cycles, check that the battery contacts inside the handset bay are clean and making firm contact with the pack.

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