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Redmi BN49 7A Replacement Battery 3.85V 3900mAh

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From $25.99 USD $31.99
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Fits Redmi 7A and replaces OEM battery BN49 across all regional variants including M1903C3EI, MZB7995IN, and MZB7798IN models.
Rated 3.85V at 3900mAh, this cell delivers 15.02Wh — sufficient to sustain the processor and display load without voltage sag under typical use cycles.
Connector aligns vertically to the board-mounted JST socket with no locking tab; seating requires firm pressure until the edge catches the retention clip.
We ran full discharge cycles on a 7A test unit with the fuel gauge IC active — BMS accepted the cell without cutoff faults and voltage held steady through the final 5% window.
On first charge after installation, disable fast charging for one complete discharge-charge cycle so the coulomb counter recalibrates against the new cell's discharge curve before high-current charging resumes.
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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

3.85V

Amp

3900mAh

Redmi 7A — 3.85V Li-Polymer Replacement Battery (BN49)

The BN49 is the stock Li-Polymer cell for the Redmi 7A smartphone, covering model variants M1903C3EI, MZB7995IN, and MZB7798IN among others. It runs at 3.85V and carries 3900mAh (15.02Wh). This replacement restores power to the display, processor, and cellular radio when the original cell has degraded or failed.

  • 7A variant compatibility: All listed model numbers — M1903C3EI, MZB7995IN, MZB7798IN and the wider 7A regional variants — share the same chassis dimensions and connector pinout, so the BN49 fits without modification to the flex cable or adhesive frame.
  • Bench tested on actual hardware: We cycled the BN49 through charge and discharge on the 7A platform, confirmed BMS handshake with the charge IC, and verified the protection circuit trips correctly at low-voltage cutoff without false positives during normal load.
  • Fuel gauge recalibration after swap: On first use after installation, disable fast charging and run one complete discharge-charge cycle at standard rate. This lets the fuel gauge IC map its coulomb counter against the new cell's discharge curve before any high-current charging session pushes current into an uncalibrated baseline.

Sudden shutdown at 20–30% on the Redmi 7A after a cell swap

This is a voltage-cliff problem, not a capacity problem. The fuel gauge IC still holds the old cell's discharge curve in memory, so its percentage reading no longer matches the new cell's actual voltage behaviour. When the modem transmits or the screen brightness spikes, current draw pulls the cell voltage below the system cutoff threshold — even though the gauge still shows 20–30%. One full slow-rate discharge-charge cycle forces the coulomb counter to re-anchor to the new cell's curve, and the shutdowns stop.

Redmi 7A not powering on after the battery sat discharged in storage

If the BN49 cell drops below approximately 2.5V during storage, the BMS enters lockout mode and blocks any charge current to prevent damage to an over-discharged cell. Plugging in a standard charger appears to do nothing — no charging LED, no boot. Connect the phone to a low-current USB source (a PC port rather than a wall adapter) and leave it for 15–20 minutes; the BMS trickle-recovery circuit will slowly raise cell voltage until it exits lockout. Once the LED shows any charge activity, switch to the wall adapter to complete the charge normally.

Compatible Models

7A M1903C3EI MZB7995IN MZB7798IN MZB7799IN M1903C3EH M1903C3EG MZB7989IN MZB7800IN MZB8008IN M1903C3EE M1903C3EC M1903C3ET 7A Dual SIM 7A Global Dual SIM 7A Standard Edition 7A Standard Edition Dual SIM 7A Premium 7A Premium Edition Dual SIM

Replaces Part Numbers

BN49

Technical Specifications

Voltage3.85V
Amp Hours3900mAh
Capacity3900mAh
Rate15.02Wh
Net Weight53.4g /1.88 oz
Gross Weight78g /2.75 oz
Approximate Weight78g /2.75 oz
Dimension 74.30 x 58.50 x 4.94mm

Product Highlights

  • Brand: Redmi
  • 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 Redmi 7A shows 25% battery and then shuts off without warning — is the new BN49 cell faulty?

The cell itself is not the fault here. The fuel gauge IC calibrated its discharge curve to your old, degraded cell, and that map no longer matches the new BN49's voltage profile. Under a sudden load spike — mobile data transmission or screen-on burst — the cell voltage drops past the system cutoff before the gauge has time to correct its reading. Run one full discharge down to auto-shutdown followed by a full uninterrupted charge at standard rate, and the coulomb counter will re-anchor to the new cell. The premature shutdowns should stop after that single cycle.

The Redmi 7A screen shows charging but the percentage jumps around erratically after fitting the BN49 — what's causing it?

Erratic percentage jumps point to the fuel gauge IC recalibrating in real time against a cell it has no reference data for. The IC is comparing live voltage readings against a stored discharge curve that belonged to the old cell, so small voltage fluctuations produce large, inconsistent percentage corrections. This is normal for the first one to three charge cycles after a cell swap. Let the phone complete two full discharge-charge cycles at standard charge rate — no fast charging — and the gauge readings will stabilise as the IC builds an accurate model of the BN49's curve.

The Redmi 7A feels warm near the battery area while charging the new BN49 — should I be concerned?

Mild warmth during the first few charge sessions on a new cell is expected. A fresh high-impedance cell presents more resistance than a broken-in one, so the charge IC dissipates slightly more heat as it drives current in. As long as the phone is not hot to the touch and charging stops automatically at 100%, the behaviour is within normal range. If the phone stays uncomfortably hot past the first three cycles, check that the charge IC is not running a fast-charge protocol against an uncalibrated cell — turn off any fast-charge setting in the battery menu until after the first full slow cycle.

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