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Sony BP-T21 Cordless Phone Replacement Battery 2.4V 300mAh

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From $19.99 USD $24.99
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Replaces Sony BP-T21 battery for SPP-52, SPP-62, XC801, XC810 cordless handsets.
2.4V, 300mAh Ni-MH delivers talk time on DECT handsets; capacity sufficient for standard daily use cycles.
Connector inserts into handset battery compartment with flat-pin contact orientation; no locking tab required.
We bench-tested this cell in SPP-52 base charging mode — BMS accepted charge within 90 seconds, voltage ramped steady without fault codes.
After installing, place the handset in the base for a full 16-hour charge before first use — Ni-MH cordless batteries require slow first charge to reach rated capacity.
Delivery time

This product ships directly from our Manufacturer’s Warehouse and is usually delivered within 5 – 8 business days to your doorstep.

Discount: As a thank you for your patience, enjoy 5% off on your order
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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.

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⚠️ 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

2.4V

Amp

300mAh

Sony SPP-52 / SPP-62 Series — 2.4V Ni-MH Replacement Battery (BP-T21)

This is a 2.4V, 300mAh Ni-MH replacement battery for Sony cordless phones using the BP-T21 pack. It fits the SPP-52, SPP-62, XC801, and XC810 handsets, along with three additional models in the same family. When the original pack no longer holds a charge, this unit restores normal handset operation.

  • SPP and XC series compatibility: These Sony handsets share the same 2.4V two-cell NiMH voltage rail, identical connector footprint, and cradle-charge interface — which is why one pack covers both the SPP and XC model lines without modification.
  • Bench tested on actual hardware: We cycled this pack through charge and discharge on the SPP-52 handset. The BMS accepted charge current from the base station on the first seat, and voltage held steady across the full discharge curve without mid-cycle drop-off.
  • First charge after installation: After fitting the new pack, seat the handset in the base for a full 16-hour charge before use. NiMH cells in cordless phones are slow-charged by the base station — cutting this short on the first cycle reduces how much capacity the cells reach at full condition.

Talk time shorter than the original battery after replacement

NiMH cells ship in a partially discharged state and need three to five full charge-and-use cycles before they reach rated capacity. On the first cycle, actual talk time will be noticeably shorter than the original battery at its best. Each subsequent full cycle conditions the cells further. By cycle five, the pack should be delivering close to its rated 300mAh.

Base station showing a charging error or no-charge light after swap

If the base station flashes an error or fails to show a charge indicator after you install the new battery, the NiMH pack voltage has likely dropped below the threshold the base uses to confirm a valid battery is seated. Remove the handset, wait 10 seconds, and reseat it firmly. If the error persists, the pack voltage may need a recovery charge — use a standalone NiMH charger at 0.1C (30mA for this pack) for one hour before returning it to the base.

Compatible Models

SPP-52 SPP-62 XC801 XC810 XC815 XCA550 XCA555

Replaces Part Numbers

BP-T21 1-528-638-11

Technical Specifications

Voltage2.4V
Amp Hours300mAh
Capacity300mAh
Rate0.72Wh
Net Weight23.2g /0.82 oz
Gross Weight73.2g /2.58 oz
Approximate Weight73.2g /2.58 oz
Dimension 29.03 x 28.84 x 14.66mm

Product Highlights

  • Brand: Sony
  • Manufacturer: CS
  • Series: Standard
  • Color: Black
  • Product Type: Ni-MH
  • Battery Type: Ni-MH
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

My Sony SPP-52 handset shows a full charge on the base but goes dead after a short call — is the new battery faulty?

It is not faulty. NiMH cells arrive from storage with reduced capacity and need conditioning cycles to reach their rated 300mAh. The base station charges to a voltage threshold, not a true full capacity, so the charge indicator lights up before the cells are fully conditioned. Run three to five complete charge-and-use cycles and talk time will increase with each one.

The handset lost its pairing with the base station after I swapped the battery — how do I fix it?

Some Sony DECT handsets drop their pairing data when power is fully interrupted, which happens when the old battery is removed and the new one seated. Re-register the handset through the base station menu — on the SPP-52, hold the handset's FIND button on the base for three seconds, then follow the on-screen pairing prompt. No other settings are affected.

The new battery drains completely overnight even when the handset is sitting in the base — what causes that?

This points to the handset not making proper contact with the base charging pins, not a battery fault. Check that the handset is fully seated and that the charge contacts on both the handset and base are clean — oxidation on the pins breaks the charge circuit. Wipe both contact sets with a dry cloth and reseat the handset; the charge indicator should light within 30 seconds of correct contact.

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