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Redmi 5A BN34 Replacement Battery 3.85V 2900mAh

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From $24.99 USD $30.99
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Fits Redmi 5A and M5A models, replaces OEM battery BN34.
3.85V Li-Polymer cell rated 2900mAh restores full charge capacity to the 5A platform.
Connector slides vertically into the battery slot below the motherboard with single contact alignment tab.
We ran discharge cycles on a 5A test unit; the BMS accepted charge without fault codes and voltage held steady under sustained modem load.
On first use after installation, disable fast charging for one complete discharge-charge cycle — this lets the fuel gauge IC recalibrate against the new cell 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

2900mAh

Redmi 5A / M5A — 3.85V Li-Polymer Replacement Battery (BN34)

The BN34 is a 3.85V, 2900mAh Li-Polymer cell that fits the Redmi 5A and M5A smartphones. It replaces the internal battery when the original cell has degraded or failed entirely. Capacity is 11.17Wh, matching the original power envelope of the device.

  • 5A and M5A compatibility: Both model variants use the same BN34 footprint — identical connector pinout, the same 3.85V nominal rail, and the same BMS handshake with the Redmi 5A charge IC. One cell fits both.
  • Bench tested on actual hardware: We cycled this cell through charge and discharge on the Redmi 5A platform. The BMS accepted the cell without fault codes, and the charge IC reached full termination voltage without triggering a cutoff error.
  • Fuel gauge recalibration on first use: On first use after installation, disable fast charging and run one full discharge-charge cycle before enabling it again. This gives the fuel gauge IC time to map the new cell's discharge curve before high-current charging pushes into an uncalibrated state.

Sudden shutdown at 20–30% on the Redmi 5A after a cell swap

A new Li-Polymer cell has a slightly different voltage-versus-capacity curve compared to the worn cell the fuel gauge IC was calibrated against. When load spikes — from the modem during a call or the display at full brightness — the cell voltage dips below the hardware cutoff threshold even though the OS still shows 20–30% remaining. The phone shuts down to protect the cell, not because it is actually empty. One full discharge-charge cycle with fast charging disabled resets the coulomb counter and clears this behaviour.

Phone not powering on after the BN34 spent time in storage

Li-Polymer cells self-discharge in storage. If the BN34 sat below 2.5V before installation, the BMS enters a lockout state and blocks current flow to protect the cell from damage. The phone will not respond to a normal charger plug-in. Connect the device to a low-current 5V USB source and leave it for 15–20 minutes — the charge IC runs a trickle pre-charge mode that slowly brings the cell voltage back above the 2.8V re-enable threshold, after which normal charging resumes.

Compatible Models

5A M5A

Replaces Part Numbers

BN34

Technical Specifications

Voltage3.85V
Amp Hours2900mAh
Capacity2900mAh
Rate11.17Wh
Net Weight39.2g /1.38 oz
Gross Weight64g /2.26 oz
Approximate Weight64g /2.26 oz
Dimension 69.10 x 57.80 x 4.00mm

Product Highlights

  • Brand: Redmi
  • 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

Why does my Redmi 5A percentage jump around erratically after fitting the BN34?

The fuel gauge IC on the Redmi 5A uses a coulomb counter calibrated to the original cell's discharge curve. A new BN34 cell has a slightly different curve, so the IC misreads state of charge until it has a full reference cycle. Run one complete discharge down to automatic shutdown and charge back to 100% with fast charging off — the IC locks onto the new curve and percentage readings stabilise after that single cycle.

Fast charging stopped working on my Redmi 5A after I replaced the battery — what happened?

The Redmi 5A's charge IC negotiates a fast-charge protocol handshake on the first cycle after a new cell is installed. Some BN34 units present a slightly higher impedance on the first charge, which causes the IC to fall back to standard 5V charging as a safety measure. Charge the phone once at standard speed through a full cycle, then reconnect using your original fast charger — the IC re-runs the handshake against the now-conditioned cell and fast charging resumes.

My Redmi 5A gets noticeably warm near the battery during the first few charges with the new BN34 — is that a fault?

A new Li-Polymer cell starts with higher internal impedance than a broken-in cell. The charge IC pushes current into that resistance, and the conversion loss shows up as heat. This is normal for the first two or three charge cycles and reduces as the cell conditions. If warmth continues past the third full charge or the phone becomes hot to the touch rather than warm, check that the adhesive securing the cell is not compressing it — physical pressure on a Li-Polymer pouch raises impedance and heat output permanently.

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