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BLU Star 4.5 Replacement Battery 3.7V 1550mAh C635404170L

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From $23.99 USD $29.99
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Fits BLU Star 4.5 and S450 smartphones; replaces OEM part C635404170L.
3.7V and 1550mAh lithium-ion cell restores full call, messaging, and app runtime on your device.
Connector slides into the factory slot with no modification; locking tab engages on insertion.
We bench-tested this cell against the original discharge curve—BMS accepted the new pack on first power cycle without lockout.
On first charge after installation, run one complete discharge-to-shutdown cycle before enabling any fast charging to let the fuel gauge IC recalibrate against the new cell's voltage profile.
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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

1550mAh

BLU Star 4.5 / S450 — 3.7V Li-ion Replacement Battery (C635404170L)

This is a 3.7V, 1550mAh Li-ion cell that fits the BLU Star 4.5 and S450 smartphones. It replaces OEM part C635404170L and restores power to a phone that no longer holds charge or shuts down unexpectedly. Capacity is 5.74Wh — matched to the original spec.

  • Star 4.5 and S450 compatibility: Both models share the same battery bay dimensions, connector pinout, and BMS handshake protocol. The cell measures 63.05 × 54.05 × 4.60mm — a match to the factory cavity on both variants.
  • Bench tested on actual hardware: We ran this cell through charge and discharge cycles on a BLU S450 unit. The BMS accepted the charge IC handshake without faults, and the fuel gauge IC tracked state-of-charge correctly after one full conditioning cycle.
  • Fuel gauge recalibration on first install: After fitting this cell, disable fast charging and run one complete discharge down to auto-shutoff, then charge uninterrupted to 100%. This lets the fuel gauge IC map its reference curve to the new cell before high-current charging begins.

Sudden shutdown at 20–30% on the BLU Star 4.5

This happens when the fuel gauge IC is still calibrated to the old cell's discharge curve. The replacement cell hits a voltage cliff under modem or display load before the OS percentage reading reaches zero. The phone interprets the voltage drop as a hard fault and cuts power. One full discharge-to-shutoff cycle followed by an uninterrupted charge to 100% forces the coulomb counter to reset its reference points against the new cell.

OS reporting wrong battery percentage after cell swap

The fuel gauge IC stores a learned discharge profile from the old cell. A new cell with different internal resistance throws that profile off immediately. You'll see the percentage jump erratically or read higher than actual. Run one full cycle — discharge to auto-shutoff, charge to 100% with the screen off — and the coulomb counter recalibrates. After that cycle, percentage reporting stabilises.

Compatible Models

Star 4.5 S450

Replaces Part Numbers

C635404170L

Technical Specifications

Voltage3.7V
Amp Hours1550mAh
Capacity1550mAh
Rate5.74Wh
Net Weight33g /1.16 oz
Gross Weight58g /2.05 oz
Approximate Weight58g /2.05 oz
Dimension 63.05 x 54.05 x 4.60mm

Product Highlights

  • Brand: BLU
  • 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 shuts off at around 25% but the battery percentage was fine all morning — what's causing this?

This is a voltage cliff failure, not a percentage tracking issue. Under sustained load — mobile data, a bright screen, or a call — the new cell's voltage drops faster than the fuel gauge IC expects based on the old cell's stored curve. The phone sees the voltage fall below the hardware cutoff threshold and shuts down, even though the displayed percentage looks safe. Run one full discharge-to-shutoff cycle followed by an uninterrupted charge to 100% to force the fuel gauge IC to remap against the new cell.

Fast charging stopped working the first time I plugged in the new battery — is the charger the problem?

The charger is likely fine. On first insertion of a replacement cell, the charge IC sometimes fails to complete the USB negotiation handshake before beginning charge — it defaults to standard 5V input instead of the fast-charge voltage. This is a one-cycle issue tied to BMS initialisation, not the charger. Unplug, wait 10 seconds, reconnect — if fast charging still doesn't engage after two attempts, complete one standard-rate charge cycle first and retry.

Phone won't turn on at all after the new battery sat in a drawer for a few weeks — how do I recover it?

A cell that drops below approximately 2.5V triggers BMS lockout to prevent damage from deep discharge. The phone will not power on and may not show a charging indicator immediately. Connect to a wall charger — not a PC port — and leave it for 20–30 minutes without pressing any buttons. The BMS needs sustained low-current trickle input to exit lockout before the phone can boot. Once the charging indicator appears, allow a full charge before powering on.

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