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Mobistel Cynus F8 Replacement Battery BTY26189 3.7V 3000mAh

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From $26.99 USD $33.99
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Fits Mobistel Cynus F8 smartphone, replaces OEM battery BTY26189.
3.7V and 3000mAh capacity restores full charge cycles on this device without voltage sag.
Connector slides straight into the Cynus F8 battery slot with standard lithium-ion contact orientation.
Bench tested on Cynus F8 hardware — BMS accepted charge within first cycle, voltage stable under load.
Disable fast charging for one full discharge-charge cycle after installation to let the fuel gauge IC recalibrate against the new cell discharge curve.
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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

3.7V

Amp

3000mAh

Mobistel Cynus F8 — 3.7V Li-ion Replacement Battery (BTY26189)

This is a 3.7V, 3000mAh (11.1Wh) Li-ion cell for the Mobistel Cynus F8 smartphone. It replaces the original BTY26189 when the factory cell has degraded or failed. Swap it in to restore full power capacity without replacing the entire handset.

  • Cynus F8 fit: The Cynus F8 uses a fixed connector pinout and a specific BMS handshake tied to BTY26189. This cell matches that pinout and communicates correctly with the phone's charge IC — no firmware flags, no rejected charge cycles.
  • Bench tested on actual hardware: We cycled this cell through the Cynus F8 charge IC and confirmed BMS acceptance, full charge termination at 4.2V, and stable voltage delivery under both screen-on and modem-active loads.
  • Fuel gauge recalibration on first install: After fitting this cell, disable fast charging if your device supports it and run one complete discharge down to automatic shutdown, then charge uninterrupted to 100%. This gives the fuel gauge IC one full cycle to map the new cell's discharge curve before it starts reporting accurate percentages.

Sudden shutdown at 20–30% on the Cynus F8 after a cell swap

A new cell has a slightly different internal resistance profile than the factory cell. The Cynus F8's fuel gauge IC holds its old calibration data after the swap. Under high-current loads — active LTE, GPS, or screen at full brightness — the new cell's voltage drops faster than the IC expects, and the phone hits its cutoff threshold before the reported percentage reaches zero. The fix is one full uninterrupted discharge-charge cycle. After that cycle, the coulomb counter resets its reference and the shutdowns stop.

Percentage jumping erratically in the first few days after installation

The Cynus F8's fuel gauge IC uses a stored discharge curve from the old cell to estimate remaining capacity. When a new cell goes in, the stored curve no longer matches actual cell behaviour — so percentage readings jump between values that don't reflect real charge state. This is a calibration gap, not a fault with the replacement cell. Run the phone from 100% down to automatic low-battery shutdown twice, charging fully between each cycle, and the IC rebuilds its reference curve against the new cell's actual voltage profile.

Compatible Models

Cynus F8

Replaces Part Numbers

BTY26189 BTY26189Mobistel/STD

Technical Specifications

Voltage3.7V
Amp Hours3000mAh
Capacity3000mAh
Rate11.1Wh
Net Weight57g /2.01 oz
Gross Weight92g /3.25 oz
Approximate Weight92g /3.25 oz
Dimension 84.00 x 64.74 x 4.85mm

Product Highlights

  • Brand: Mobistel
  • Manufacturer: CS
  • Series: X-Longer
  • Color: Black
  • Product Type: Li-ion
  • Battery Type: Li-ion
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

My Cynus F8 shuts off at around 25% after I put the new battery in — is the cell faulty?

The cell is not faulty. The phone's fuel gauge IC still holds the discharge curve from your old, degraded cell, so it misreads how much voltage the new cell has left under load. When the modem or screen draws hard current, the voltage dips faster than the IC expects and the phone shuts off early. Run one full discharge to automatic shutdown and then charge to 100% without interruption — the coulomb counter resets its reference and the early shutdowns clear.

The phone feels warm near the battery area while charging with the new cell — is that normal?

Some warmth during the first few charge cycles is expected. A new high-impedance cell has slightly higher internal resistance than a broken-in one, so the charge IC pushes a bit more heat through it until the cell completes its initial formation cycles. If the phone stays warm but not hot to the touch and cools down once fully charged, that is normal behaviour. If it stays hot at 100% or the charger cuts off early, check that you are using the original Mobistel charge cable and adapter — third-party adapters can hold the charge IC in a high-current state longer than the circuit expects.

My Cynus F8 won't turn on at all after the replacement battery sat in a drawer for a few months before I installed it — how do I recover it?

Lithium-ion cells self-discharge in storage, and if the BTY26189 dropped below approximately 2.5V per cell during storage, the BMS locks out to prevent damage from deep discharge. Plug the phone into the original charger and leave it connected for 20–30 minutes before pressing the power button — the charge IC trickle-charges the cell at low current to bring it back above the BMS recovery threshold. If the screen shows no charging indicator at all after 30 minutes, try a different USB cable, as a resistive connection can prevent the trickle charge from starting.

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