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Hyundai TS21B Replacement Battery 3.7V 1000mAh Li-ion

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From $23.99 USD $29.99
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Fits Hyundai TS21B smartphone; replaces the original 3.7V Li-ion cell that lost capacity.
3.7V, 1000mAh delivers the same energy profile as OEM pack for calls and messaging.
Connector slides into the battery slot with standard orientation; locking tab seats flush against the housing.
We cycled the cell through full charge-discharge on a Hyundai test platform; BMS accepted the pack without lockout.
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 stresses an uncalibrated BMS.
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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

1000mAh

Hyundai TS21B — 3.7V Li-ion Replacement Battery

This is a 3.7V Li-ion cell rated at 1000mAh (3.7Wh), built to fit the Hyundai TS21B smartphone. It replaces the original cell when capacity has dropped, charge no longer holds, or the phone shuts off unexpectedly. Voltage and connector match the TS21B's charge IC and BMS requirements.

  • TS21B cell compatibility: The TS21B runs a single-cell 3.7V nominal Li-ion configuration. The replacement cell matches that voltage rail and physical connector — the BMS negotiates charge current the same way it does with the factory cell.
  • Bench tested on actual hardware: We cycled this cell through charge and discharge under typical smartphone load profiles. The BMS accepted the cell without error flags, and charge termination triggered correctly at full voltage.
  • Fuel gauge recalibration after swap: On first use after installation, disable fast charging for one complete discharge-charge cycle. This gives the fuel gauge IC time to map the new cell's discharge curve before high-current charging pushes current into an uncalibrated state.

Sudden shutdown at 20–30% on the TS21B after a cell swap

This happens because the fuel gauge IC is still reading the old cell's discharge curve. The new cell hits a voltage cliff under modem or screen load before the gauge reaches zero. The phone interprets the voltage drop as a fault and shuts down — not a defective cell, but an uncalibrated gauge. Run one full discharge to near-zero and a full charge to 100% to let the coulomb counter reset against the new cell's actual curve.

TS21B percentage jumping erratically after replacement

Erratic percentage readings on the TS21B after a cell swap point to the fuel gauge IC recalibrating against new internal resistance values. The coulomb counter was tuned to the worn original cell and now overestimates or underestimates state of charge. This stabilises after one or two full discharge-charge cycles. Charge from below 5% to 100% without interruption to accelerate recalibration.

Compatible Models

TS21B

Technical Specifications

Voltage3.7V
Amp Hours1000mAh
Capacity1000mAh
Rate3.7Wh
Gross Weight100g /3.53 oz
Approximate Weight100g /3.53 oz

Product Highlights

  • Brand: Hyundai
  • Manufacturer: CS
  • Series: Standard
  • Color: Silver
  • Product Type: Li-ion
  • Battery Type: Li-ion
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

My Hyundai TS21B powers off at around 25% after I put in the new battery — is the cell faulty?

The cell is almost certainly fine. The fuel gauge IC on the TS21B was calibrated to the old cell's discharge curve, so it misreads the new cell's voltage cliff under load — typically when the modem or display draws a peak current burst. The phone sees the voltage drop as a cutoff condition and shuts down before the gauge reaches zero. Run one uninterrupted discharge to below 5% and a full charge to 100% to let the coulomb counter recalibrate to the new cell.

Fast charging stopped working on my TS21B after I replaced the battery — it only charges slowly now.

On the first cycle after a cell swap, some charge ICs default to a low-current trickle mode until the BMS confirms the new cell is within expected impedance range. This is a safety handshake, not a fault. Let the phone complete one full slow charge to 100%, then reconnect the charger — the charge IC typically accepts the higher current profile on the second cycle once it has logged a completed charge sequence against the new cell.

The TS21B won't turn on at all after the replacement battery sat in a drawer for a few months — what happened?

Li-ion cells self-discharge during storage, and if the cell dropped below approximately 2.5V, the BMS entered lockout mode to prevent damage from deep discharge. The phone will not power on from this state with a normal charger. Connect to a charger and leave it for 20–30 minutes without pressing the power button — most BMS circuits on single-cell smartphones begin a recovery trickle charge from lockout and will allow a normal boot once the cell reaches around 3.0V.

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