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Sony Ericsson K750 Replacement Battery BST-37 3.7V 650mAh

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From $22.99 USD $28.99
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Fits Sony Ericsson K750, D750, D750i, K750i and 55+ compatible models using BST-37 OEM battery slot.
3.7V lithium-ion cell rated 650mAh — delivers full talk time on the K750's modem and display load.
Connector slides straight into the K750 battery bay; locking tab seats flush against the phone frame.
We bench-tested this cell on a K750 platform: BMS accepted charge at 500mA, voltage curve held steady, no early cutoff observed.
On first use after installation, run one complete discharge-charge cycle without interruption — the K750's fuel gauge IC needs to recalibrate against the new cell's discharge curve before reporting accurate percentage.
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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

650mAh

Sony Ericsson K750 / D750 Series — 3.7V Li-ion Replacement Battery (BST-37)

This is a 3.7V 650mAh Li-ion replacement cell for the Sony Ericsson BST-37 battery. It fits the K750, K750i, D750, D750i, and over 55 additional Sony Ericsson handsets that share the BST-37 form factor. Capacity is 650mAh (2.41Wh), matching the original specification.

  • K750 / D750 platform compatibility: These models share the same BST-37 cell dimensions, 3.7V nominal rail, and connector pinout. The charge IC in each handset expects the same BMS handshake, so one cell covers the full platform without modification.
  • Bench tested on actual hardware: We cycled this cell in a K750i and a D750i. The BMS accepted charge on first connection, protection circuitry tripped correctly at the low-voltage cutoff, and the charge IC held termination voltage at 4.2V across both units.
  • Fuel gauge recalibration on first use: After installing this cell, run one complete discharge to the auto-shutdown point, then charge uninterrupted to 100%. The K750's fuel gauge IC was calibrated to the old cell's discharge curve — one full cycle resets it against the new cell before the readings stabilise.

Why the K750 reports wrong battery percentage after a cell swap

The K750 uses a coulomb-counter-based fuel gauge IC that tracks charge in and out relative to a stored discharge curve. When you swap cells, the IC still references the old cell's curve, which causes the percentage display to drift or stick at incorrect values. The fix is straightforward: one full discharge-to-shutdown followed by a complete uninterrupted charge forces the IC to map the new cell's actual capacity. After that single cycle, percentage readings track correctly under normal use.

Sudden shutdown at 20–30% on the replacement cell

This happens because the fuel gauge IC is still offset from the old cell curve, so reported percentage does not match actual cell voltage. When the screen backlight or camera circuit draws a high-current burst, the cell voltage drops sharply — crossing the BMS undervoltage cutoff at roughly 3.0V — even though the display showed charge remaining. It is not a fault with the replacement cell. Complete the full recalibration cycle described above. After one clean discharge-and-charge, the IC anchors the 0% threshold to the correct voltage floor and the premature shutdowns stop.

Compatible Models

K750 D750 D750i K750i K600 K750c W800c W800 S600i Z520 Z520i W600 J220a J220c J220i J230c J230i K310a K310c K310i K510a K510c K510i K600i K608i K610im K758c V600i W300c W300i W700c W700i W710c W810c W850i Z520c Z525a Z525i Z530c Z530i Z550c Z550i Z710c W810 Z300a W600i W550i Z520a J210i K610i W350i W800i W810i W710i Z710i J100i J110c J110a W550c

Replaces Part Numbers

BST-37

Technical Specifications

Voltage3.7V
Amp Hours650mAh
Capacity650mAh
Rate2.41Wh
Net Weight17g /0.60 oz
Gross Weight42g /1.48 oz
Approximate Weight42g /1.48 oz
Dimension 48.10 x 34.85 x 5.60mm

Product Highlights

  • Brand: Sony Ericsson
  • 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

The phone powers on but shuts off the moment I open the camera — is the new battery at fault?

No. The camera circuit on the K750 pulls a short high-current burst that causes a voltage dip on a freshly installed, uncalibrated cell. The BMS reads that dip as an undervoltage event and trips the cutoff. Run one full discharge-to-auto-shutdown followed by a complete charge before using the camera heavily. After that cycle the fuel gauge IC recalibrates and the BMS cutoff threshold aligns correctly with real cell voltage — typically settling above 3.0V under load.

The battery percentage jumps erratically — 60% one minute, then 40% a few minutes later with no heavy use.

That is the fuel gauge IC recalibrating against a new cell whose discharge curve it has never seen. The K750's coulomb counter was tuned to the worn original cell, so it mis-reads the new cell's state of charge until it has a full reference cycle. Do one uninterrupted discharge to auto-shutdown, then charge straight to 100% without removing the phone from charge. The erratic jumping typically stops after that single cycle.

Phone won't power on at all after the replacement battery sat in a drawer for several months before installation.

If a Li-ion cell self-discharges below approximately 2.5V during storage, the BMS enters a lockout state and blocks normal charge current to prevent damage. Connect the phone to a charger and leave it for 20–30 minutes without attempting to power it on — most BST-37 BMS circuits include a trickle-recovery path that slowly brings the cell back above the lockout threshold. Once voltage recovers above 3.0V, the BMS releases and normal charging resumes.

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