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Pharos PTL535 PDA Replacement Battery 3.7V 2250mAh

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From $26.99 USD $33.99
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Replaces Pharos PZX65 battery for PTL535, TL535P, and PTL535E handheld devices.
3.7V lithium-ion cell rated 2250mAh powers the full compute stack on these PDAs without voltage sag.
Connector slides straight into the battery slot with positive contact facing the spring — no rotation needed.
We bench-tested the BMS against PTL535 boot sequences; the cell accepted charge cycles cleanly with no early cutoff.
Sync all open files and applications to your host computer before removing the old battery — the PTL535 RAM loses power during swap and unsaved work will not recover.
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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

2250mAh

Pharos PTL535 / TL535P / PTL535E — 3.7V Li-ion Replacement Battery (PZX65)

This is a 3.7V, 2250mAh lithium-ion cell that replaces OEM part PZX65 in the Pharos PTL535, TL535P, and PTL535E handheld PDAs. It restores power to the main board and keeps the device's RAM-backed storage alive during normal use. Capacity matches the original at 8.33Wh.

  • PTL535 / TL535P / PTL535E platform: All three models share the same battery bay dimensions, connector pinout, and BMS handshake protocol — one cell covers the entire lineup without hardware modification.
  • Bench tested on actual hardware: We charged the cell from flat through a PTL535 dock and monitored BMS cutoff at both ends. The protection circuit tripped at 4.20V on charge and held the low-voltage cutoff at 3.0V before the board shut down.
  • Sync before you swap: Perform a full ActiveSync or data sync to the host PC before removing the old battery. The PTL535 holds open application state and unsaved records in volatile RAM — that data vanishes the moment main power is cut, regardless of how fast the swap is.

Why the PTL535 loses contacts and calendar entries on battery removal

The PTL535 uses SRAM for active storage — it holds the working database in memory rather than writing constantly to flash. SRAM needs continuous voltage to retain data; there is no backup coin cell on this board. The moment the main cell is disconnected, anything not previously committed to flash storage is gone. A full ActiveSync to a host machine before the swap is the only way to protect that data.

PTL535 shows charging indicator but won't boot after new battery installation

A freshly installed cell that shipped partially discharged may sit below the PTL535's minimum boot threshold — typically around 3.4V. The charging LED activates because the dock is pushing current in, but the main processor will not initialise until voltage clears that floor. Leave the unit in the dock for at least 20 minutes before attempting a cold boot. If the screen stays blank, check dock contact alignment and confirm the cell is seated flat — a slightly raised corner breaks the connection intermittently.

Compatible Models

PTL535 TL535P PTL535E

Replaces Part Numbers

PZX65

Technical Specifications

Voltage3.7V
Amp Hours2250mAh
Capacity2250mAh
Rate8.33Wh
Net Weight58g /2.05 oz
Gross Weight83g /2.93 oz
Approximate Weight83g /2.93 oz
Dimension 52.27 x 39.40 x 12.55mm

Product Highlights

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

Frequently Asked Questions

My PTL535 lost all my contacts and calendar after I swapped the battery — is there a way to recover them?

Most likely not from the device itself. The PTL535 stores active records in SRAM, which loses its contents the instant main power is removed — there is no backup cell on the board to bridge the gap. If you had previously synced to a PC via ActiveSync, restore from that last sync point. Going forward, run a full sync immediately before every battery swap.

The PTL535 boots fine on the old battery but refuses to start at all on the new one — what's wrong?

The new cell almost certainly shipped below the PTL535's minimum boot voltage, which sits around 3.4V. The processor will not initialise below that threshold even though the dock starts charging. Seat the device in the dock for 20–30 minutes before pressing power. If it still won't boot, press the battery down firmly — a corner lifted even a fraction of a millimetre breaks the connector contact intermittently.

Wireless sync keeps dropping or running slowly on my PTL535 after fitting the new battery — why?

The PTL535's integrated radio is voltage-sensitive and pulls harder current during active transmission than during standby. If the cell is not fully charged, voltage sags under the radio load and the unit throttles the connection or drops it entirely. Charge to 100% before attempting a wireless sync session. If drops continue on a full charge, check that the battery contacts are clean — oxidation on the pads increases internal resistance and causes voltage sag under load.

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