Apple Watch Series S6 40mm Replacement Battery 3.85V 260mAh
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Apple Watch Series S6 40mm Replacement Battery 3.85V 260mAh - is backordered and will ship as soon as it is back in stock.
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Battery Care Tips
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
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
⚠️ 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.
Apple Watch Series S6 40mm Replacement Battery 3.85V 260mAh - is backordered and will ship as soon as it is back in stock.
Voltage
3.85V
Amp
260mAh
Apple Watch Series S6 40mm — 3.85V Li-Polymer Replacement Battery (A2345)
This 3.85V, 260mAh Li-Polymer cell is the direct replacement for the Apple Watch Series S6 40mm. It fits the 40mm case only — not the 44mm variant. Swap it when the original cell no longer holds charge through a full day of normal use.
- S6 40mm cell dimensions: The A2345 cell measures 25.30 × 18.50 × 4.60mm. The 44mm S6 uses a physically larger cell with a different part number. Fitting the wrong size risks pressure damage to the display and incorrect BMS handshake with the S6's power management IC.
- Bench tested on actual hardware: We ran this cell through charge-discharge cycles on S6 hardware. The BMS accepted the cell without error flags, the fuel gauge recalibrated after a full charge from near-zero, and health reporting in watchOS stabilised within two full cycles.
- Post-swap charge protocol: After fitting this cell, place the watch on its magnetic charger immediately and charge to 100% before first use. The S6 fuel gauge IC loses its reference point when the cell is disconnected. Without a full charge cycle from near-zero, the percentage display will read inaccurately for days.
Why the S6 fuel gauge reads wrong after a cell swap
Apple Watch uses a coulomb-counter IC that tracks charge state relative to a known baseline. Removing the cell clears that baseline entirely. When a new cell is fitted, the IC has no reference, so it estimates — often badly. A full charge to 100% from a low state gives the IC a fixed endpoint to anchor its model. Until that anchor exists, watchOS will show erratic percentages that do not reflect actual capacity.
Watch not pairing with iPhone after battery replacement
Removing the battery cuts power to the BLE radio mid-session. The iPhone retains the old session key, but the watch boots with no active session — the two sides are out of sync. This is not a hardware fault. On the iPhone, open the Watch app, go to General → Reset, and select "Erase Apple Watch Content and Settings," then re-pair. The watch will reconnect cleanly and restore from backup.
Compatible Models
Replaces Part Numbers
Technical Specifications
Product Highlights
- Brand: Apple
- Manufacturer: CS
- Series: Standard
- Color: Black
- Product Type: Li-Polymer
- Battery Type: Li-Polymer
- Warranty: 12 Months
- Bulk Orders: sales@batteryweb.com
Frequently Asked Questions
My Apple Watch S6 shows 0% and won't turn on right after I replaced the battery — did I get a dead cell?
The cell is almost certainly fine. The S6 fuel gauge IC loses its charge reference when power is removed during the swap, so it defaults to 0% on first boot. Place the watch on its magnetic charger immediately and let it charge uninterrupted to 100%. Do not power it on mid-charge. Once it hits 100%, the IC sets a new reference point and the display will read correctly.
New battery draining completely in one day on my S6 40mm — it used to last much longer before I swapped it.
For the first few days after a cell swap, the fuel gauge model is still recalibrating, so drain appears faster than it actually is. If heavy drain continues past three full charge cycles, check whether Always-On Display and continuous heart rate monitoring are both active — on the 40mm's 260mAh cell, those two features running simultaneously pull the highest sustained current the platform sees. Turn off Always-On Display under Settings → Display & Brightness and confirm heart rate is set to automatic rather than continuous. Recheck drain after one full cycle.
The magnetic charger clicks on but the watch won't charge after I replaced the A2345 cell — charge ring just pulses.
A pulsing charge ring with no progress usually means the charging contacts on the watch back are not seating flush against the magnetic puck. During reassembly, the back cover can shift by less than a millimetre and misalign the contacts. Remove the watch from the charger, inspect the back for any raised edge or debris around the contact points, and re-seat the cover firmly before placing it back on the charger. If the ring still pulses, clean the watch-back contacts and charger surface with a dry cloth and retry.
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