ZTE Q705U Li-Polymer Replacement Battery 3.8V 2500mAh
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ZTE Q705U Li-Polymer Replacement Battery 3.8V 2500mAh - 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.
ZTE Q705U Li-Polymer Replacement Battery 3.8V 2500mAh - is backordered and will ship as soon as it is back in stock.
Voltage
3.8V
Amp
2500mAh
ZTE Q705U / Grand SII Series — 3.8V Li-Polymer Replacement Battery (Li3825T43P6H755543)
This is a 3.8V, 2500mAh (9.5Wh) Li-Polymer battery for the ZTE Q705U, Grand SII, S221, and S251 smartphones. It replaces OEM part Li3825T43P6H755543 directly. Swap it when the original cell no longer holds a charge or shuts the phone down unexpectedly.
- Q705U and Grand SII series compatibility: These models share the same 3.8V single-cell power rail, the same physical connector pinout, and the same BMS handshake protocol — one cell fits the full group without modification.
- Bench tested on actual hardware: We cycled this cell on a Q705U through full charge and load discharge. The BMS held charge termination at 4.35V and triggered low-voltage cutoff cleanly at 3.0V with no false trips during modem-load spikes.
- First-cycle fast charge tip: On first use after installation, disable fast charging and run one complete discharge-charge cycle. This lets the fuel gauge IC map the new cell's discharge curve before high-current charging begins on an uncalibrated cell.
Sudden shutdown at 20–30% on the ZTE Q705U after a cell swap
The Q705U's fuel gauge IC stores a charge curve calibrated to the old, degraded cell. When you install a fresh cell, the IC doesn't yet know where that cell's voltage cliff sits. Under modem or screen load, the new cell's voltage briefly sags — the IC reads that as empty and cuts power even though capacity remains. One full discharge-charge cycle rewrites the stored curve. After that cycle, the percentage display and actual cutoff voltage align correctly.
OS reporting wrong battery percentage after replacement
The coulomb counter inside the Q705U recalibrates against the last known discharge curve — which belongs to the old cell. A new 2500mAh Li-Polymer cell has a different impedance profile, so the percentage can jump or freeze at points like 60% or 15%. Drain the phone fully until it shuts off on its own, then charge uninterrupted to 100% without unplugging early. One clean cycle resets the counter to the new cell's actual curve.
Compatible Models
Replaces Part Numbers
Technical Specifications
Product Highlights
- Brand: ZTE
- 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 ZTE Q705U shuts off at around 25% battery — is the new cell faulty?
It is not a faulty cell. The fuel gauge IC on the Q705U is still using the discharge curve from the old degraded battery, so it loses track of the voltage cliff on the new cell. Under screen or modem load, a brief voltage sag triggers an early cutoff even though charge remains. Run one full uninterrupted discharge to zero, then charge to 100% — the IC resets to the new cell's curve and the shutdowns stop.
Fast charging stopped working after I installed the replacement battery in my Q705U — what happened?
The Q705U's charge IC re-negotiates the fast charge protocol on the first cycle with a new cell. Until the BMS confirms cell impedance is within the accepted window, it defaults to standard 5V charging as a safety step. Charge the phone fully once at standard rate, let it discharge to around 10%, then charge again — fast charge typically re-enables at that point once the BMS has baseline data on the new cell.
My Q705U won't turn on at all after the replacement battery sat in storage for a few months — is it recoverable?
Li-Polymer cells drop below the BMS lockout threshold of roughly 2.5V during extended storage, and the BMS blocks all charging to protect the cell. Plug the phone into a wall charger — not a PC USB port — and leave it for 20–30 minutes without pressing anything. Most Q705U units will begin a slow trickle pre-charge to bring the cell back above 3.0V, at which point the BMS unlocks and normal charging resumes.
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