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Panasonic KX-TU301 Compatible Battery CGA-LB102 3.7V 700mAh

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Fits Panasonic KX-TU301, KX-TU321, KX-TU311 and replaces OEM part number CGA-LB102.
3.7V lithium-ion at 700mAh capacity delivers the original discharge curve for this candybar phone's modem and display load.
Connector slides into the battery slot with a single locking tab that seats flush against the housing wall.
We ran this cell on the KX-TU301 platform and confirmed the BMS fuel gauge accepts the new discharge profile after one full cycle.
On first charge after installation, let the phone fully discharge and recharge without interruption — the coulomb counter IC needs one complete cycle to recalibrate against this cell's curve before normal use.
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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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🔹 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

3.7V

Amp

700mAh

Panasonic KX-TU301 Series — 3.7V Li-ion Replacement Battery (CGA-LB102)

This is a 3.7V, 700mAh Li-ion replacement battery for the Panasonic KX-TU301 candybar mobile phone and related models. It slots directly into the KX-TU301, KX-TU301 GME, KX-TU321, and KX-TU311, among others. OEM part number CGA-LB102.

  • KX-TU301 series compatibility: These models share the same battery bay dimensions, 3.7V nominal voltage rail, and CGA-LB102 connector pinout. The BMS handshake is identical across the range, so one cell covers the full group.
  • Bench tested on actual hardware: We ran this cell through a full charge-discharge cycle on a KX-TU301 unit. The BMS accepted the charge handshake cleanly, voltage held steady at 3.7V nominal under load, and the phone registered capacity without error flags.
  • Fuel gauge recalibration on first use: After fitting this cell, disable any fast-charge accessory for the first complete discharge-charge cycle. The phone's fuel gauge IC is calibrated to the old cell's discharge curve. One full cycle at standard current lets it recalibrate against the new cell before any high-current charging is applied.

Why the KX-TU301 reports wrong battery percentage after a cell swap

The phone's fuel gauge IC uses a stored discharge curve built from the original cell's behaviour over time. When you install a new cell, that curve no longer matches the actual charge state. The gauge reads percentage against old data, so it shows incorrect numbers — often jumping or sitting too high or too low. One complete discharge to auto-off followed by a full charge resets the coulomb counter and aligns the gauge to the new cell's actual curve.

Sudden shutdown at 20–30% on the replacement cell

This happens when the fuel gauge IC has not yet recalibrated and the displayed percentage does not reflect true cell voltage. The phone reads 25% but the cell has already dropped below the BMS cutoff threshold — around 3.0V under the load of an active call or screen wake. The BMS trips and the phone shuts off without warning. Run one full discharge-charge cycle at standard current first; after recalibration, the displayed percentage will track actual cell voltage and the shutdowns stop.

Compatible Models

KX-TU301 KX-TU301 GME KX-TU321 KX-TU311 KX-TU325 KX-TW221 KX-TU320 KX-TU327 KX-TU328

Replaces Part Numbers

CGA-LB102

Technical Specifications

Voltage3.7V
Amp Hours700mAh
Capacity700mAh
Rate2.59Wh
Net Weight18g /0.63 oz
Gross Weight43g /1.52 oz
Approximate Weight43g /1.52 oz
Dimension 44.40 x 34.20 x 6.90mm

Product Highlights

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

Frequently Asked Questions

The phone turned off at around 25% and now won't power on at all — is the battery dead?

The BMS locked out after the cell dropped below roughly 3.0V under load while the fuel gauge was still showing a false percentage. This is a BMS protection lockout, not a dead cell. Connect the phone to a wall charger — not a PC USB port — and leave it for 20–30 minutes without pressing the power button. Once the cell recovers above the BMS re-enable threshold (around 3.0V), the phone will start charging normally and power on.

The phone feels warm near the battery compartment while charging the new cell — is that normal?

A fresh high-impedance cell draws charge current less efficiently on the first few cycles, which causes the charge IC to dissipate slightly more heat than usual. This is normal for the first two or three charge cycles and settles as the cell's internal resistance drops with use. If the warmth is concentrated at the battery cover and fades after the first few charges, no action is needed. If the phone stays hot well into later cycles, check that you are using a Panasonic-rated 5V charger, not a high-output USB-C adapter pushing more current than the charge IC expects.

After fitting the new battery, the percentage jumps around erratically — goes from 60% to 80% in minutes without charging.

The fuel gauge IC is still running the discharge model it built for the old, degraded cell. Against a new cell with a different discharge curve, the coulomb counter produces unstable readings. The fix is one complete cycle: run the phone down until it shuts off automatically, then charge uninterrupted to 100% using the standard wall charger. After that single cycle the fuel gauge resets its reference points against the new cell and percentage readings stabilise.

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