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Jitterbug SPH-A120 Replacement Battery 3.7V 750mAh

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From $23.99 USD $29.99
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Fits Jitterbug SPH-A120 flip phone; replaces BST5339WA, BST5339DA, BTIA10G battery packs.
3.7V, 750mAh lithium-ion cell delivers 2.78Wh to restore full charge cycles on aging Jitterbug handsets.
Connector slides straight into battery slot with positive terminal facing outward; locking tab seats flush against frame.
We ran full discharge cycles on the SPH-A120 — BMS accepted voltage handshake on first insertion, no fault delays.
On first power-on after install, let the phone complete one full discharge-charge cycle before relying on battery percentage display; the fuel gauge IC needs one cycle to recalibrate against this cell's discharge curve.
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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

750mAh

Jitterbug SPH-A120 — 3.7V Li-ion Replacement Battery (BST5339WA)

This 3.7V, 750mAh Li-ion cell replaces the original battery in the Jitterbug SPH-A120 and SPHA120CAB flip phones. It matches OEM part numbers BST5339WA, BST5339DA, and BTIA10G. Voltage and physical dimensions are matched to the original spec to ensure the BMS accepts the new cell without a handshake error.

  • SPH-A120 and SPHA120CAB fitment: Both models share the same battery bay geometry, connector pinout, and BMS communication protocol — one cell fits both without modification.
  • Bench tested on actual hardware: We cycled this cell through charge, standby, and call-load draw. The BMS accepted the cell on first connection, held the charge curve within spec, and tripped the protection circuit correctly at the low-voltage threshold.
  • Fuel gauge recalibration after swap: On first use after installation, run one full discharge down to automatic cutoff, then charge uninterrupted to 100%. This gives the fuel gauge IC a clean reference point against the new cell's discharge curve before the phone starts reporting percentage.

Why the SPH-A120 reports wrong battery percentage after a cell swap

The SPH-A120 uses a fuel gauge IC that builds its percentage model from the coulomb counter data of the previous cell. When you swap the battery, that stored curve no longer matches the new cell's actual capacity. The phone reads voltage and maps it to the old model, so it can show 60% when the cell is nearly flat. One full discharge-to-cutoff followed by a complete uninterrupted charge resets the reference and brings the percentage readings back in line.

Sudden shutdown at 20–30% on the replacement cell

This happens when the fuel gauge IC hasn't recalibrated and the cell hits a voltage cliff faster than the meter predicts. Under the load of an outgoing call, the cell voltage drops sharply — the protection circuit reads it as a low-voltage fault and cuts power before the displayed percentage reaches zero. It's not a faulty cell; it's an uncalibrated gauge. Run one complete discharge-charge cycle without interruption and the shutdowns stop. If they continue past two full cycles, check that the terminal voltage at full charge reaches 4.2V.

Compatible Models

SPH-A120 SPHA120CAB

Replaces Part Numbers

BST5339WA BST5339DA BTIA10G

Technical Specifications

Voltage3.7V
Amp Hours750mAh
Capacity750mAh
Rate2.78Wh
Net Weight20g /0.71 oz
Gross Weight45g /1.59 oz
Approximate Weight45g /1.59 oz
Dimension 64.86 x 47.07 x 8.27mm

Product Highlights

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

Frequently Asked Questions

The phone turned off by itself and now won't power on at all — is the battery completely dead?

Most likely the BMS has tripped into lockout after the cell voltage dropped below 2.5V during storage or extended discharge. Connect the phone to a charger and leave it for at least 20 minutes without attempting to power it on — the charge IC needs to push a small trickle current into the cell before the BMS will release the lockout. If the phone still won't respond after 30 minutes on charge, check that the charger is delivering at least 5V to the port.

The battery percentage jumps around erratically — it'll show 45%, then 70%, then drop to 10% within minutes.

The fuel gauge IC on the SPH-A120 is recalibrating against the new cell's discharge curve, and until it has a full cycle to work from, the coulomb counter produces unstable readings. Run one full discharge down to automatic shutdown, then charge straight through to 100% without unplugging. That single cycle gives the IC enough data to lock onto the correct curve, and the erratic jumping stops.

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

A new high-impedance cell draws slightly more current during the initial charge cycle because the internal resistance hasn't settled yet. Mild warmth at the battery cover is expected for the first one or two charges. If the phone becomes hot to the touch or the charger disconnects on its own, remove the battery and inspect the contacts for debris or misalignment. Normal surface temperature during charge on this cell should stay below 40°C.

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