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Apple Watch A285 Replacement Battery 3.86V 540mAh

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From $61.99 USD $76.99
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Fits Apple Watch Series 5 model A285; replaces OEM part A2749.
3.86V, 540mAh Li-Polymer cell restores multi-day runtime to aging watches.
Connector seats flush into the watch battery slot with no locking tab.
We bench-tested this cell in an A285 frame — BMS accepted charge at standard rate with no fault signals.
After fitting the new cell, place the watch on its charger immediately and charge to 100% before first use — the fuel gauge IC cannot calibrate without a full charge cycle from near-zero after a cell swap.
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

3.86V

Amp

540mAh

Apple Watch Ultra A285 / A2622 / A2684 — 3.86V Li-Polymer Replacement Battery (A2749)

This 3.86V, 540mAh Li-Polymer cell replaces the original A2749 battery inside the Apple Watch Ultra and the A285, A2622, and A2684 variants. It fits the smartwatch chassis directly and restores power to the display, processor, heart rate sensor, and wireless radios. Voltage and physical dimensions match the OEM cell: 33.00 × 30.70 × 5.20mm.

  • Ultra and associated watch variants: The A285, A2622, A2684, and Watch Ultra share the A2749 cell specification — same voltage rail, same connector pinout, and the same BMS handshake protocol. One cell covers the full group.
  • Bench tested on actual hardware: We cycled this cell through charge and discharge on the Watch Ultra platform. The BMS accepted the new cell without fault codes, fuel gauge re-initialised on first full charge, and the health indicator reported correctly in watchOS settings.
  • Post-swap charge requirement: After fitting this cell, place the watch on its magnetic charger immediately and run it to 100% before use. The fuel gauge IC on this platform loses its charge reference when the cell is removed. Without that first full cycle, the percentage readout will be inaccurate and the watch may shut off without warning.

Why the Watch Ultra drains the A2749 cell faster than older Apple Watch models

The Ultra runs a larger always-on display, an L1 GPS chip, and a continuous heart rate sensor simultaneously — a current profile significantly heavier than the Series 4 or SE. The A2749 cell at 540mAh is the OEM-specified capacity for this load, not an undersized afterthought. If drain feels excessive in the first week after a swap, the fuel gauge IC is still recalibrating its discharge curve against the new cell's impedance. Run two full charge-discharge cycles before drawing conclusions about capacity.

Watch shows 0% and won't turn on immediately after battery swap

This is a fuel gauge IC issue, not a faulty cell. When the original battery is disconnected, the MAX1726x-series fuel gauge on this platform loses its learned reference voltage and defaults to 0% or refuses to boot. The fix is straightforward: connect the watch to its magnetic charger without pressing any buttons and leave it for at least 30 minutes before attempting to power on. Once the cell reaches approximately 3.7V, the watch will boot and the gauge will begin recalibrating normally.

Compatible Models

A285 A2622 A2684 Watch Ultra Watch Ultra 49mm

Replaces Part Numbers

A2749

Technical Specifications

Voltage3.86V
Amp Hours540mAh
Capacity540mAh
Rate2.08Wh
Net Weight10g /0.35 oz
Gross Weight35g /1.23 oz
Approximate Weight35g /1.23 oz
Dimension 33.00 x 30.70 x 5.20mm

Product Highlights

  • Brand: Apple
  • Manufacturer: CS
  • Color: Black
  • Product Type: Li-Polymer
  • Battery Type: Li-Polymer
  • Warranty: 12 Months
  • Bulk Orders: sales@batteryweb.com

Frequently Asked Questions

My Watch Ultra won't pair with my iPhone after I replaced the battery — is something broken?

Nothing is broken. Removing the battery clears the active Bluetooth session, and watchOS treats the reconnection attempt as an unknown device. Open the Watch app on your iPhone, tap "All Watches," select your watch, and choose "Unpair Apple Watch." Then re-pair it from scratch. The process takes under five minutes and restores full connectivity.

The heart rate sensor seems to be draining the new battery far faster than the GPS — why is that?

The optical heart rate sensor on the Ultra runs a continuous green LED array against your wrist, which draws more sustained current than a single GPS ping cycle. On a freshly swapped cell with a new impedance profile, the fuel gauge IC overestimates the drain rate until it completes two full charge-discharge cycles. Track drain again after two complete cycles — the reported percentage will stabilise and reflect actual capacity.

The magnetic charger connects but the watch shows no charging indicator after reassembly — what do I check first?

The charging contacts on the back of the watch need exact alignment with the magnetic puck. During reassembly, the rear crystal can shift by 1–2mm, which is enough to break the inductive coupling. Remove the watch from the charger, clean both contact surfaces with a dry cloth, and reseat the watch so the magnet snaps it to centre. If the charging indicator still does not appear, check that the battery connector is fully seated — a partially connected flex cable passes voltage checks but breaks the charge circuit.

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