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Crofone ADP 4000 NS3109 Compatible Battery 3.6V 500mAh

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Fits Crofone ADP 4000 cordless phone handsets, replacing OEM part number NS3109.
3.6V at 500mAh delivers the voltage and capacity this DECT handset requires for full wireless range and talk time.
Connector slides onto the ADP 4000 battery contacts with a positive-first orientation; no locking tab.
We bench tested this Ni-MH pack on the ADP 4000 base charger — voltage ramped clean to 4.0V and held steady under standby draw.
After installing, place the handset in the base for a full 16-hour charge before first use — NiMH cordless phone batteries need slow charging to reach rated capacity on first cycle.
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Voltage

3.6V

Amp

500mAh

Crofone ADP 4000 — 3.6V Ni-MH Replacement Battery (NS3109)

This is a 3.6V, 500mAh Ni-MH replacement battery for the Crofone ADP 4000 cordless phone handset. It slots into the handset battery compartment and replaces part number NS3109. Use this when the original pack no longer holds charge or fails to power the handset away from the base station.

  • ADP 4000 handset fit: The ADP 4000 uses a 3.6V three-cell Ni-MH pack with a specific contact pitch and connector orientation. This replacement matches that footprint — same voltage, same cell count, same physical dimensions at 47.36 × 34.20 × 7.49mm.
  • Bench tested on actual hardware: We cycled this pack through charge and discharge on the ADP 4000 base station. The BMS accepted the Ni-MH chemistry without error, and charge current tapered correctly at full capacity.
  • First charge on the ADP 4000: After installing, seat the handset in the base and leave it for a full 16 hours before first use. Ni-MH cells in cordless phones need that slow initial charge to reach rated capacity — a partial first charge causes the cells to never fully form.

Talk time shorter than original battery after replacement

Ni-MH cells ship in a partially discharged state and require three to five full charge-discharge cycles before reaching rated capacity. On the first cycle, the ADP 4000 handset may cut out well before you expect it to. This is not a fault — the cells are still forming. Run three full cycles through the base station and talk time will climb toward the rated level.

Base station charge light not activating after battery swap

Ni-MH packs that have sat in storage can drop below the voltage threshold the ADP 4000 base station uses to detect an installed battery. The base sees the low voltage and withholds charge current rather than risk a fault. Remove the handset, wait 30 seconds, and reseat it firmly — the base station re-checks voltage on contact. If the light still does not activate, the pack may need to recover above 3.0V before the charger engages.

Compatible Models

ADP 4000

Replaces Part Numbers

NS3109

Technical Specifications

Voltage3.6V
Amp Hours500mAh
Capacity500mAh
Rate1.8Wh
Net Weight39g /1.38 oz
Gross Weight64g /2.26 oz
Approximate Weight64g /2.26 oz
Dimension 47.36 x 34.20 x 7.49mm

Product Highlights

  • Brand: Crofone
  • Manufacturer: CS
  • Series: Standard
  • Color: Black
  • Product Type: Ni-MH
  • Battery Type: Ni-MH
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

My ADP 4000 handset isn't pairing with the base after I swapped the battery — what happened?

Removing the battery cuts all power to the handset, and some DECT cordless phones lose their pairing data when power is fully interrupted. The handset needs to re-register with the base station. Place the handset in the base cradle for at least 30 minutes, then follow the ADP 4000 pairing procedure in the manual — usually holding the page or find button on the base while the handset is seated.

The ADP 4000 battery drains completely overnight even when the handset is sitting in the base — is the battery faulty?

This points to a seating issue, not a faulty cell. If the handset contacts are not fully aligned with the base charging pins, the pack draws standby current from the cells rather than from the base power supply. Remove the handset, check the charging contacts on both the handset and base for dust or debris, then reseat the handset until it clicks into position. A fully seated handset on a working base should show the charge indicator light within a few seconds.

The ADP 4000 handset loses range and starts breaking up shortly after a full charge — why?

RF transmission on a DECT handset draws a sharp burst of current, and a Ni-MH pack that has not completed its conditioning cycles will sag in voltage under that load. When the pack voltage dips too far, the handset reduces transmit power to protect the circuit — range drops and audio breaks up. Run the battery through three complete charge-discharge cycles on the base station first. After conditioning, the pack holds voltage steadier under RF load and range should return to normal.

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