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Samsung Galaxy S20 FE 5G EB-BG781ABU Replacement Battery 3.86V 4400mAh

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From $26.99 USD $33.99
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Fits Galaxy S20 FE 5G models SM-G781U1/DS, SM-G781W, and variants; replaces EB-BG781ABU, EB-BG781ABE, EB-BG781ABY.
3.86V, 4400mAh lithium-polymer cell matches OEM output; restores full capacity on a device that typically degrades 15–20% annually.
Connector slides straight into the battery slot with no locking tab; orientation marked on the cell itself.
We cycled this cell against the fuel gauge IC on a G781U board; BMS accepted charge without fault codes or thermal drift.
On first use after installation, disable fast charging for one full discharge-charge cycle so the coulomb counter recalibrates against the new 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

3.86V

Amp

4400mAh

Samsung Galaxy S20 FE 5G — 3.86V Li-Polymer Replacement Battery (EB-BG781ABU)

This is a 3.86V, 4400mAh Li-Polymer replacement battery for the Samsung Galaxy S20 FE 5G. It fits SM-G7810, SM-G781U1/DS, SM-G781W, and related variants sharing the EB-BG781ABU connector and BMS handshake. Voltage and capacity match the original cell specification exactly.

  • S20 FE 5G model variants: The SM-G781 series shares a common power rail, flex connector, and fuel gauge IC interface across regional variants. One battery covers the full lineup because the BMS communication protocol does not differ between carrier and unlocked hardware.
  • Bench tested on actual hardware: We cycled this cell through charge and discharge on an SM-G781 unit. The BMS accepted the cell without fault flags, fast charge negotiated normally after the first full cycle, and the fuel gauge IC tracked state-of-charge without erratic jumps.
  • First-cycle calibration on the S20 FE 5G: On first use after installation, disable fast charging and run one complete discharge-charge cycle. This lets the fuel gauge IC recalibrate its coulomb counter against the new cell's discharge curve before high-current fast charging pushes current into an uncalibrated state.

Sudden shutdown at 20–30% on the S20 FE 5G after a cell swap

An aged or freshly installed cell can hit a voltage cliff well above 0% indicated charge. When the 5G modem, display, and processor draw peak current simultaneously, cell voltage drops sharply. If it falls below the BMS cutoff threshold — typically around 3.2V under load — the phone shuts off even though the fuel gauge still reads 20–30%. One full discharge-charge cycle lets the coulomb counter relearn the actual usable voltage window of the new cell and eliminates most of these shutdowns.

OS reporting wrong battery percentage after replacement

The Galaxy S20 FE 5G stores its fuel gauge calibration data against the discharge curve of the original cell. A new cell has a slightly different internal resistance and voltage profile, so the saved calibration no longer maps accurately to real state-of-charge. This shows up as percentage jumps, a meter that reads 100% immediately after a short charge, or a number that holds steady for a long stretch then drops quickly. Charge the phone to 100%, let it discharge fully until it shuts down on its own, then charge uninterrupted back to 100% — that single cycle resets the coulomb counter to the new cell's curve.

Compatible Models

Galaxy S20 FE 5G SM-G7810 SM-G781U1/DS SM-G781W SM-G781B/DS Galaxy S20 Fan Edition SM-G780G/DS SM-G780F SM-G780F/DSM SM-G781U1 SM-G781U SM-G781A SM-G781B

Replaces Part Numbers

EB-BG781ABU EB-BG781ABE EB-BG781ABY GH43-05052A GH82-24205A

Technical Specifications

Voltage3.86V
Amp Hours4400mAh
Capacity4400mAh
Rate16.98Wh
Net Weight59g /2.08 oz
Gross Weight109g /3.84 oz
Approximate Weight109g /3.84 oz
Dimension 75.72 x 62.13 x 5.12mm

Product Highlights

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

Frequently Asked Questions

My S20 FE 5G won't turn on at all after the replacement battery sat in a drawer for a few months — is the cell dead?

Probably not dead, but the BMS has gone into lockout. Li-Polymer cells that self-discharge below roughly 2.5V per cell trigger a protection cutoff that blocks normal charging to prevent thermal runaway on a deeply discharged cell. Plug the phone into a low-current charger — a 5W USB-A brick, not a fast charger — and leave it for 30–60 minutes without pressing the power button. The BMS trickle-charges the cell back above the recovery threshold, then normal charging resumes; if the screen shows a battery icon with a lightning bolt, the recovery is working.

Fast charging stopped working on my S20 FE 5G right after I put in the new battery — the phone just slow-charges now.

This is normal on the first cycle with a new cell. The USB-PD handshake and Samsung Adaptive Fast Charge protocol both require the BMS to report a stable cell state before the charge IC allows high-current delivery. On a fresh cell the BMS is still in its initial assessment window, so the charge IC defaults to a safe low-current rate. Complete one full charge to 100% on a standard charger, then reconnect the fast charger — the BMS will have logged a full cycle and the fast charge protocol will negotiate correctly.

The S20 FE 5G feels warm near the back cover while charging with the new battery — is that a fault?

Mild warmth during the first few charge cycles is expected with a new high-impedance cell. A fresh Li-Polymer cell has slightly higher internal resistance than a cell that has been cycled a few times, so the charge IC dissipates a little more energy as heat during the constant-current phase. Keep the phone out of its case for the first two or three charges so heat can dissipate freely. If the back becomes hot enough to be uncomfortable to hold — above roughly 45°C — stop charging and check that the charging port and cable are clean and seated fully.

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