Redmi 9s BN55 Replacement Battery 3.85V 4800mAh
This product ships directly from our Manufacturer's Warehouse and is usually delivered within 7 – 10 business days to your doorstep.
WECARE5
Check that your old battery model number and device model to match our description. This makes sure they work together.
We ship your order same day if you buy it before 4 PM EST.
Redmi 9s BN55 Replacement Battery 3.85V 4800mAh - is backordered and will ship as soon as it is back in stock.
Let customers speak for us
Send Your Battery Photo
Expert Technician Help
Snap a photo or video of your battery and send it to us. We'll identify the exact replacement—fast and hassle-free. Our team has helped thousands of customers find the right battery quickly and easily.
POST YOUR BATTERY IMAGE
Product & Solutions Expert
✉ sales@batteryweb.com
Battery Care Tips
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
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
⚠️ 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.
Redmi 9s BN55 Replacement Battery 3.85V 4800mAh - is backordered and will ship as soon as it is back in stock.
Voltage
3.85V
Amp
4800mAh
Redmi 9s — 3.85V Li-Polymer Replacement Battery (BN55)
This is a 3.85V, 4800mAh Li-Polymer replacement battery for the Xiaomi Redmi 9s smartphone. It carries OEM part number BN55 and fits the Redmi 9s directly. Use it when the original cell no longer holds charge or the phone shuts down unexpectedly under load.
- Redmi 9s fit: The BN55 cell was released as the sole battery configuration for the Redmi 9s. The connector, BMS handshake voltage, and physical footprint — 89.10 × 64.80 × 4.65mm — match the original bay without modification.
- Bench tested on actual hardware: We cycled this cell through full discharge and charge sequences on a Redmi 9s. The BMS accepted charge correctly, and the fuel gauge IC tracked state-of-charge without triggering erratic readings or unexpected cutoffs.
- First-cycle fast charge protocol: On first use after installation, disable fast charging and complete one full discharge-charge cycle at standard rate. This lets the fuel gauge IC recalibrate its coulomb counter against the new cell's discharge curve before high-current charging pushes into an uncalibrated state.
Sudden shutdown at 20–30% on the Redmi 9s after a cell swap
This happens because the fuel gauge IC is still using the discharge curve it mapped for the old, degraded cell. When the new cell hits a voltage point the IC wasn't expecting, it interprets it as critically low and commands a shutdown — even though charge remains. The fix is one complete discharge-charge cycle with fast charging disabled. After that cycle, the coulomb counter re-maps against the new cell and percentage readings stabilise.
Redmi 9s not powering on after the BN55 sat in storage
Li-Polymer cells that self-discharge in storage can drop below 2.5V per cell, triggering a BMS lockout that blocks normal charging. The phone will show no sign of life when plugged in. Connect to a wall charger — not a PC USB port — and leave it for 20–30 minutes without pressing the power button. Once the BMS detects sufficient voltage recovery, the charge IC re-engages and the phone will boot normally.
Compatible Models
Replaces Part Numbers
Technical Specifications
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
My Redmi 9s shows the correct percentage for a while, then suddenly jumps down and shuts off — is this a faulty battery?
It's not a faulty cell — it's the fuel gauge IC running on a calibration curve mapped to your old, degraded battery. The new BN55 cell has a different discharge profile, so the IC misjudges the voltage cliff and triggers a shutdown earlier than the actual charge state warrants. Run one full discharge down to automatic shutdown, then charge to 100% at standard rate with fast charging off. After that single cycle, the coulomb counter re-maps to the new cell and the shutdowns stop.
Fast charging stopped working on my Redmi 9s after I installed the replacement BN55 — the phone only charges slowly now.
On the first cycle with a new cell, the charge IC sometimes defaults to standard current until it validates the BMS handshake from the replacement battery. This is normal behaviour, not a fault. Complete one full charge-discharge cycle at standard rate, then re-enable fast charging in Settings > Battery. If fast charging still doesn't engage after that, check that you're using the original Redmi charger — third-party adapters often don't send the correct voltage handshake to trigger the fast charge protocol.
The Redmi 9s feels noticeably warm near the back panel while charging the new battery — should I be concerned?
A new Li-Polymer cell typically has higher internal impedance than a well-cycled cell, so the charge IC works slightly harder during the first few charge cycles, generating more heat. This is temporary and normal. Charge on a hard, flat surface rather than a pillow or case, and avoid using the phone heavily while it charges for the first two or three cycles. If the warmth persists beyond the third full charge cycle, check that the adhesive backing on the BN55 is seated flat against the chassis — a raised cell reduces heat dissipation to the frame.
Payment & Security
Payment methods
Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.
Related Products
Engineered for Performance. Built to Last.
Check out our top-rated selection of reliable products built to last. We offer high-quality options that deliver consistent performance for all your needs.
-
Up to 21% offNew arrival
BatteryWeb
Samsung Galaxy Note 10 Lite EB-BN770ABY Replacement Battery 3.85V 4300mAh
0.24 lb
Sale priceFrom $26.99 USD Regular price $33.99Unit priceIn stock (66 units) -
-
Up to 21% offNew arrival
BatteryWeb
Xiaomi Mi 10 Pro Replacement Battery BM4M 3.85V 4200mAh
0.25 lb
Sale priceFrom $30.99 USD Regular price $38.99Unit priceIn stock (153 units) -
-
Up to 20% offNew arrival
BatteryWeb
BL299 Lenovo Z5s Replacement Battery 3.85V 3250mAh
0.21 lb
Sale priceFrom $25.99 USD Regular price $31.99Unit priceIn stock (81 units) -
-
Up to 21% offNew arrival
BatteryWeb
Pocophone Poco M2 Pro Replacement Battery 3.85V 4800mAh
0.25 lb
Sale priceFrom $30.99 USD Regular price $38.99Unit priceIn stock (60 units) -
-
Up to 21% offNew arrival
BatteryWeb
Xiaomi Redmi 9s BN55 Replacement Battery 3.85V 4800mAh
0.25 lb
Sale priceFrom $30.99 USD Regular price $38.99Unit priceIn stock (60 units) -
-
Up to 21% offNew arrival
BatteryWeb
Nokia 6.2 LC-620 Compatible Battery 3.85V 3400mAh
0.21 lb
Sale priceFrom $30.99 USD Regular price $38.99Unit priceIn stock (66 units) -
-
Up to 21% offNew arrival
BatteryWeb
Apple iPhone 11 Compatible Battery 3.83V 3100mAh 616-00641
0.21 lb
Sale priceFrom $30.99 USD Regular price $38.99Unit priceIn stock (180 units) -
-
Up to 20% offNew arrival
BatteryWeb
Apple iPhone 11 Pro Max 616-00351 Replacement Battery 3950mAh
0.24 lb
Sale priceFrom $39.99 USD Regular price $49.99Unit priceIn stock (72 units) -
