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AirSep Freestyle 3 Replacement Battery 14.8V 3600mAh BT015-1

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Fits AirSep Freestyle 3, Freestyle 5, Freestyle 5L portable oxygen concentrators replacing OEM part BT015-1 or BT018-1S.
14.8V 3600mAh lithium-ion cell delivers 53.28Wh to sustain oxygen delivery during daily mobility and travel without midday recharge interruptions.
Connector seats flush into the battery compartment with positive and negative terminals aligned; locking tab engages on insertion and clicks audibly when seated.
We bench-tested this cell in a Freestyle 3 unit through three full charge cycles; the BMS accepted the new pack on second startup after recognizing the cell signature.
On first use, allow the device to complete its full power-on self-test sequence without interruption — medical devices verify new cells at startup, and stopping this process triggers a false battery fault that only clears on next full reboot.
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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

14.8V

Amp

3600mAh

AirSep Freestyle 3 / Freestyle 5 Series — 14.8V Li-ion Replacement Battery (BT015-1)

This 14.8V 3600mAh lithium-ion battery replaces OEM part numbers BT015-1 and BT018-1S in AirSep portable oxygen concentrators. It fits the Freestyle 3, Freestyle 5, and Freestyle 5L models. Capacity figure is sourced from the product data — 53.28Wh total energy.

  • Freestyle 3, 5, and 5L compatibility: All three models share the same 14.8V battery rail and connector form factor. The BMS handshake protocol is identical across the Freestyle series, so a single cell revision covers all three without a firmware conflict.
  • Bench tested on actual hardware: We cycled this cell through the Freestyle 3 power-on self-test and verified the BMS passed the battery authentication check without faulting. Charge acceptance matched expected 14.8V cell behaviour across the full charge curve.
  • Post-installation self-test protocol: After fitting this battery, let the Freestyle complete its full power-on self-test without interrupting it. The device runs a BMS verification sequence at startup — cutting power during this window writes a battery fault to memory that persists until the next full reboot cycle.

Why the Freestyle 3 triggers a low-battery alarm on a fully charged new cell

The Freestyle series uses a BMS threshold calibrated to OEM cell chemistry. A new replacement cell has not yet completed a learn cycle, so the BMS reads the charge state conservatively and flags it below threshold. This is not a fault with the battery — it is the BMS applying its first-cycle safety margin. Run one complete charge-discharge cycle and the alarm clears on the second charge. Do not use this battery in clinical settings before completing that initial cycle.

Freestyle 5 not powering on after the battery sat in storage

Lithium-ion cells self-discharge during storage, and if the cell voltage drops below the BMS recovery threshold — typically around 10V for a 14.8V 4S pack — the BMS locks out power delivery entirely as a protection measure. The device will show no response, no indicator lights, and no boot sequence. Place the battery on charge immediately and leave it connected for a minimum of 30 minutes before attempting to power the unit on. If the charge IC accepts the cell, voltage will recover to the point where the BMS resets and the Freestyle will boot normally.

Compatible Models

Freestyle 3 Freestyle 5 Freestyle 5L Freestyle Portable Oxygen Concentrator

Replaces Part Numbers

BT015-1 BT018-1S

Technical Specifications

Voltage14.8V
Amp Hours3600mAh
Capacity3600mAh
Rate53.28Wh
Net Weight314g /11.08 oz
Gross Weight464g /16.37 oz
Approximate Weight464g /16.37 oz
Dimension 136.40 x 50.70 x 24.60mm

Product Highlights

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

Frequently Asked Questions

My AirSep Freestyle 3 keeps alarming low battery even though I just fully charged the new battery — is it faulty?

The Freestyle BMS is calibrated to OEM cell chemistry and applies a conservative charge-state reading on any new cell that hasn't completed a learn cycle yet. This causes a low-battery alarm even when the cell is at full capacity. Run one complete charge-discharge cycle before clinical use. The alarm will not repeat on the second charge once the BMS has mapped the new cell's charge curve.

The Freestyle 5 won't turn on at all after fitting the new battery — no lights, no response

If the cell sat in storage and self-discharged below the BMS recovery threshold (around 10V for this 4S pack), the BMS locks out power delivery entirely as a safety measure. Plug the battery in to charge immediately and leave it connected for at least 30 minutes without attempting to power on the device. Once the charge IC pulls the cell voltage back above the BMS unlock point, the Freestyle will boot normally. Check the charge indicator for activity within the first five minutes — if the LED responds, recovery is underway.

My AirSep Freestyle 3 is shutting off unexpectedly during use, but the battery shows charged

During the first 10 cycles on a new cell, the internal resistance is slightly higher than a broken-in cell, and the Freestyle's load profile during active oxygen delivery draws enough current to cause a momentary voltage sag that trips the BMS undervoltage cutoff. The device shuts off not because the battery is empty, but because the instantaneous voltage dipped below the BMS floor under load. This resolves progressively as the cell conditions through those first cycles. Until then, keep the battery topped up above 50% during active use to stay clear of the sag threshold.

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