C11P2003 Asus ZenFone 8 Replacement Battery 3.87V 3900mAh
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C11P2003 Asus ZenFone 8 Replacement Battery 3.87V 3900mAh - is backordered and will ship as soon as it is back in stock.
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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.
C11P2003 Asus ZenFone 8 Replacement Battery 3.87V 3900mAh - is backordered and will ship as soon as it is back in stock.
Voltage
3.87V
Amp
3900mAh
Asus ZenFone 8 ZS590KS — 3.87V Li-Polymer Replacement Battery (C11P2003)
This is a 3.87V, 3900mAh (15.09Wh) Li-Polymer cell for the Asus ZenFone 8 (ZS590KS). It replaces OEM part numbers C11P2003 and 0B200-03950000. Fit this battery when your ZenFone 8 no longer holds a charge through a normal day of use.
- ZenFone 8 / ZS590KS fitment: Both model references — ZenFone 8 and ZS590KS — share the same physical cell format, connector pinout, and BMS handshake. One replacement covers both designations.
- Bench tested on actual hardware: We ran this cell through charge and discharge on ZS590KS hardware. The BMS accepted the cell without fault codes, and the charge IC cycled normally through trickle, CC, and CV stages.
- First-cycle fast charge protocol: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC recalibrate its coulomb counter against the new cell's actual discharge curve before high-current charging pushes into an uncalibrated register.
Sudden shutdown at 20–30% on the ZenFone 8 after a cell swap
A new cell has a discharge curve the fuel gauge IC has never seen before. The IC's stored curve still maps to the old, degraded cell, so the voltage-to-percentage translation is wrong. Under heavy load — 5G modem, screen at full brightness — the new cell can sag below the shutdown threshold before the gauge shows zero. One full discharge-charge cycle rewrites the coulomb counter registers and corrects this. After calibration, shutdowns below 20% stop.
USB-PD fast charge not triggering on the first cycle after replacement
After fitting a new cell, the charge IC sometimes defaults to standard 5V/1A input and won't negotiate USB-PD or HyperCharge rates. This happens because the BMS initialises conservatively when it detects a cell it hasn't profiled yet. Complete one full standard charge cycle first — let the battery reach 100% and drain to below 10% naturally. On the second charge, connect your original Asus fast charger; the BMS will accept the higher voltage negotiation once the cell profile is established.
Compatible Models
Replaces Part Numbers
Technical Specifications
Product Highlights
- Brand: Asus
- 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 ZenFone 8 keeps shutting off at around 25% after I put in the new battery — is something wrong with the cell?
Nothing is wrong with the cell. The fuel gauge IC is still running the discharge curve from the old degraded battery, so its percentage reading drifts from the new cell's actual voltage. Under modem or screen load, the cell voltage drops below the shutdown floor before the gauge reaches zero. Run one full discharge down to automatic shutdown, then charge uninterrupted to 100% — that single cycle resets the coulomb counter to match the new cell curve.
The battery percentage on my ZenFone 8 jumps around erratically after the replacement — it went from 60% to 45% in two minutes without me doing anything heavy.
This is the fuel gauge IC recalibrating. It lost its reference when the old cell was removed and is now estimating charge state against an uncalibrated curve. The jumps are largest in the mid-range where the new cell's voltage slope differs most from the stored profile. Complete two full discharge-charge cycles without interrupting either, and the percentage readout will stabilise.
My ZenFone 8 feels warm near the bottom of the phone while charging the new battery — is the charge IC overloading the cell?
Mild warmth during the first few charges on a new Li-Polymer cell is normal. A fresh, high-impedance cell converts slightly more charge energy to heat until the cell's internal resistance settles after a few cycles. If the phone is hot to the touch or charging stops with an error, remove the cable immediately and inspect the installation. For routine warmth below uncomfortable-to-hold, charge at standard 5V/1A for the first two cycles, then return to fast charging.
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