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Pharos PTL535 PDA Replacement Battery 3.7V 1250mAh

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From $22.99 USD $28.99
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Fits Pharos PTL535, PTL535x, PTL535e, and PZX65 pocket PC devices; replaces OEM part number PZX65.
3.7V 1250mAh lithium-ion cell delivers full capacity for scheduling, contacts, and data management on handheld PDA devices.
Connector seats flush into the battery slot with positive and negative contacts aligned; no locking tab present.
We cycled the cell through five full charge-discharge runs on a PTL535 test unit; BMS engaged normally with no early cutoff or thermal throttling observed.
Sync your PDA to the host computer before battery removal — the device stores open files and application state in RAM powered by the main cell, and power loss erases unsaved data.
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.

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

1250mAh

Pharos PTL535 Series — 3.7V Li-ion Replacement Battery (PZX65)

This 3.7V 1250mAh Li-ion cell replaces the original PZX65 battery in Pharos PTL535, PTL535x, and PTL535e pocket PCs. The PTL535 line is a handheld PDA platform used for scheduling, contacts, and mobile data tasks. Swap this cell when the original no longer holds a charge or fails to power the device through a full session.

  • PTL535 platform compatibility: The PTL535, PTL535x, and PTL535e share the same battery bay geometry and connector pinout. All three accept the PZX65 cell and use the same BMS communication protocol, so no firmware or hardware modification is needed.
  • Bench tested on actual hardware: We cycled this cell through charge and discharge on the PTL535 platform. The BMS accepted the cell without error flags, balanced charge terminated correctly at 4.2V, and the device completed full boot without voltage sag triggering a low-power cutoff.
  • Pre-swap sync requirement: Perform a full ActiveSync or Windows Mobile Device Center sync to your host computer before removing the battery. The PTL535 stores open application state and unsaved data in volatile RAM powered directly by this cell — cutting power without syncing will wipe that data.

Why the PTL535 won't boot after a battery swap

A freshly shipped Li-ion cell typically arrives at 30–50% charge — below the minimum voltage the PTL535 boot sequence needs to complete. The device will appear dead or loop back to a blank screen. Charge the new battery for at least two hours before attempting the first boot. Do not interpret a blank screen at first insertion as a faulty cell.

PTL535 showing low battery within hours of a full charge

If the battery indicator drops quickly after a full charge, the most common cause is a calibration mismatch — the device's fuel gauge is still reading against the degraded capacity curve of the old cell. Run the PTL535 down to auto-shutoff, then charge uninterrupted to 100% to force a gauge recalibration. If the problem persists after two full cycles, check that the dock or USB charge cable is delivering stable current — intermittent charge connections reset the cycle mid-session and prevent the BMS from logging a complete charge event.

Compatible Models

PTL535 PTL535x PZX65 PTL535e PTL535PB PTL535P Traveler GPS 535 Traveler GPS 535E PTL535v

Replaces Part Numbers

PZX65

Technical Specifications

Voltage3.7V
Amp Hours1250mAh
Capacity1250mAh
Rate4.63Wh
Net Weight24g /0.85 oz
Gross Weight49g /1.73 oz
Approximate Weight49g /1.73 oz
Dimension 51.54 x 38.98 x 6.64mm

Product Highlights

  • Brand: Pharos
  • 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

I swapped the battery on my Pharos PTL535 and now my contacts and calendar are gone — what happened?

The PTL535 stores live application data in SRAM that runs directly off the main battery. The moment the old cell was removed and before the new one made contact, that RAM lost power and the contents were wiped. This is not a fault with the replacement cell — it is how the platform works. Before any future battery swap, sync fully to a host computer via ActiveSync or Windows Mobile Device Center so your data is backed up before the cell is disconnected.

My PTL535 boots but drops to the low-battery warning almost immediately after I fit the new battery — is something wrong with the cell?

Nothing is wrong with the cell. The PTL535's battery gauge was calibrated to the old cell's worn-down capacity curve, so it misreads the new cell and reports low charge even when the cell is at 70–80%. Run the device down to automatic shutoff, then charge uninterrupted until the indicator reads full. After two full discharge-charge cycles the gauge recalibrates to the new cell's actual 1250mAh capacity and the readings stabilise.

The PTL535 loses connection or drops wireless sync partway through a transfer after the battery swap — what's causing that?

The PTL535's wireless radio is voltage-sensitive and will disconnect or throttle when the cell voltage dips under load. If the new battery was not fully charged before the sync attempt, the radio draw pulls the cell below its stable operating threshold and the connection drops. Charge the battery to 4.2V — a full, uninterrupted charge from the dock — before running a wireless sync session. If you are syncing large data sets, use a USB cable connection until the cell has completed at least one full charge cycle.

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