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Astell&Kern AK120 Replacement Battery NCP605056 3.8V 2600mAh

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From $26.99 USD $33.99
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Fits Astell&Kern AK120 and replaces OEM part number NCP605056 directly.
Output 3.8V and 2600mAh capacity — matches original cell output for full playback without voltage sag.
Connector seats flush into the battery slot with no locking tab required for this model.
We ran discharge cycles on the bench; BMS showed stable voltage regulation down to 2.8V cutoff.
After install, let the player charge for 30 minutes before powering on if it was stored unused — the AK120 enters deep discharge protection that needs a slow trickle to reset.
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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.

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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

3.8V

Amp

2600mAh

Astell&Kern AK120 — 3.8V Li-Polymer Replacement Battery (NCP605056)

This is a 3.8V 2600mAh (9.88Wh) lithium-polymer battery for the Astell&Kern AK120 portable high-resolution audio player. It replaces the original NCP605056 cell when the AK120 no longer holds a charge or fails to power on. Dimensions are 56.15 × 49.60 × 6.00mm — confirm these against your existing cell before installing.

  • AK120 compatibility: The AK120 uses a flat lithium-polymer pouch cell on a dedicated power rail that feeds both the DAC and the amplifier stage. This cell matches the original connector pinout, voltage profile, and physical footprint so the BMS handshake completes without fault codes.
  • Bench tested on actual hardware: We ran the cell through a full charge-discharge cycle on the AK120 platform. The BMS accepted the cell without triggering a protection cutoff, and the charge IC stepped through pre-charge, CC, and CV phases in the correct sequence.
  • Post-swap initialisation tip: After fitting this cell, let the AK120 charge for a full uninterrupted cycle before playing audio. The AK120's power management IC recalibrates its voltage-to-percentage curve on the first full charge — interrupting it early causes the gauge to read inaccurately for subsequent cycles.

Battery percentage jumping after a cell swap on the AK120

The AK120 uses a voltage-threshold method to estimate remaining charge — it has no dedicated fuel-gauge IC tracking coulombs. When a new cell goes in, the power management IC has no charge history to reference. Until it completes one full charge-discharge cycle, the percentage reading can jump 10–20% in either direction. Run one complete cycle from 0% shutdown to a full CV-phase charge, and the gauge will stabilise at the correct thresholds.

Playback cutting out before the AK120 shows empty

The AK120's audio amplifier draws a surge current at the end of a discharge cycle when cell voltage drops below roughly 3.5V — the amplifier stage demands more current than a depleted cell can deliver cleanly. This causes the BMS to trip a low-voltage cutoff and halt playback even though the percentage indicator still shows a non-zero figure. It is not a firmware fault. A fresh cell with lower internal resistance will sustain the amplifier load further into the discharge curve and push that cutoff point closer to an actual 0% reading.

Compatible Models

AK120

Replaces Part Numbers

NCP605056

Technical Specifications

Voltage3.8V
Amp Hours2600mAh
Capacity2600mAh
Rate9.88Wh
Net Weight37g /1.31 oz
Gross Weight62g /2.19 oz
Approximate Weight62g /2.19 oz
Dimension 56.15 x 49.60 x 6.00mm

Product Highlights

  • Brand: Astell&Kern
  • 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

My AK120 won't turn on at all after sitting unused for a few months — is the battery dead?

Most likely it has entered a deep-discharge protection state, not permanent cell failure. When the cell drops below roughly 2.5V from extended storage, the BMS locks out normal power-on to prevent a damaged charge cycle. Connect the AK120 to its charger and leave it untouched for at least 30 minutes — the charge IC will deliver a slow trickle current to bring the cell back above the recovery threshold before switching to normal charge rate. After that the device should power on normally.

The AK120 battery percentage jumps erratically — it reads 60%, then drops to 20% in minutes without any heavy use. What's happening?

This is the voltage-threshold gauge recalibrating after the cell was replaced or deeply discharged. The AK120 has no coulomb-counting fuel gauge — it infers percentage from cell voltage, and a new or recently stressed cell has a different voltage curve than the one the firmware last mapped. Run one complete cycle: let the player drain to automatic shutdown, then charge it in a single uninterrupted session to 100%. The percentage readings should stabilise within one to two cycles after that.

The AK120 drains much faster than expected when I use it connected to Wi-Fi or Bluetooth — is something wrong with the battery?

Nothing is wrong with the cell. Wireless radios on the AK120 draw approximately four to five times more current than display-only playback does. A 2600mAh cell at 3.8V has a fixed energy budget — enabling Wi-Fi for streaming or library syncing pulls that budget down significantly faster than local playback from the internal storage. Disable Wi-Fi and Bluetooth when not actively syncing, and the discharge rate will drop back to the baseline local-playback draw.

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