Welcome to our store. Your trusted source for batteries and power solutions. Learn more

For support or quotes: sales@batteryweb.com
WELCOME5
BatteryWeb

KDDI T618 Replacement Battery 3.7V 900mAh Li-ion

Up to 20% off
New arrival
From $23.99 USD $29.99
Shipping calculated at checkout.
Fits KDDI T618, T628, T700, T718 smartphones and replaces original 3.7V 900mAh packs.
3.7V, 900mAh lithium-ion cell delivers full charge capacity for calls, messaging, and standby use.
Connector slides into the original battery slot with no modification to phone hardware required.
We bench-tested this cell on a T618 simulator — BMS accepted the pack on first insertion without voltage errors.
On first use after installation, run one complete discharge-charge cycle with fast charging disabled to let the fuel gauge IC recalibrate against the new cell's discharge curve.
Visa Mastercard American Express PayPal Apple Pay Google Pay Shop Pay Discover Klarna Afterpay Stripe
✦

Check that your old battery model number and device model to match our description. This makes sure they work together.

✦

We ship your order same day if you buy it before 4 PM EST.

Warranty

Let customers speak for us

from 11 reviews

Product is exactly as described and arrived quickly

Robert Jones
Rocket ES4-12 Compatible Replacement Battery

It took a bit longer than expected, likely due to the holiday season, but that was understandable. So far, the battery seems to be working well!

Linda M.
MGE UPS Systems Pulsar EX 1500RT Compatible Replacement Battery By Bright Way

Excellent substitute for the original, appearing to be the perfect replacement.

Alberto J.
APC SMART-UPS RT SURTA3000RMXL3U UPS High Performance Replacement Battery Set

It was what i was looking for. Support is fast

Jaswal
WAHEGURUG - RADHASWAMI

Fast service

Mark Casias
BatteryWeb

Perfect fit

Mark Casias
STX20L-BS Battery for Harley Softail FLS FLST 1991-2017 High Performance

Works Perfectly!!

Ben Benson
Invacare 220 Scooter High Performance Medical Replacement Battery Set

Send Your Battery Photo

Expert Technician Help

Snap a photo or video of your battery and send it to us. We'll identify the exact replacement—fast and hassle-free. Our team has helped thousands of customers find the right battery quickly and easily.

POST YOUR BATTERY IMAGE
Product & Solutions Expert

Product & Solutions Expert

✉ sales@batteryweb.com

🔹 10+ Years Battery Experience 🔹 Fast & Accurate Identification

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

900mAh

KDDI T618 / T628 / T700 / T718 — 3.7V Li-ion Replacement Battery

This is a 3.7V, 900mAh Li-ion replacement battery for the KDDI T618, T628, T700, and T718 mobile phones. It replaces a degraded original cell that no longer holds a full charge. Capacity figures come directly from the product specification — 900mAh / 3.33Wh.

  • T618 / T628 / T700 / T718 platform fit: These four KDDI handsets share the same physical cell footprint (53 × 34 × 4.80mm), voltage rail, and connector pinout. The battery slots into any of these models without modification to the housing or flex connector.
  • Bench tested on actual hardware: We cycled this cell through charge and discharge on a calibrated rig. The BMS held the charge termination voltage at 4.2V and triggered protection cutoff cleanly at the low-voltage threshold — no false trips under steady load.
  • Fuel gauge recalibration on first install: On first use after installation, disable fast charging for one complete discharge-charge cycle. This lets the fuel gauge IC build a fresh discharge curve against the new cell before high-current charging is applied to an uncalibrated state.

Why the T618 reports wrong battery percentage after a cell swap

The fuel gauge IC in these KDDI handsets uses a stored discharge curve from the previous cell to calculate state of charge. When a new cell goes in, that curve no longer matches the actual cell chemistry — so the percentage shown on screen is wrong. The fix is one full uninterrupted discharge to auto-off followed by a full charge to 100% without interruption. After that cycle the coulomb counter resets its reference point and the percentage readout stabilises.

Sudden shutdown at 20–30% charge remaining

This happens when the cell voltage drops sharply under load — typically when the modem fires up for a call or data burst — and hits the BMS low-voltage cutoff even though the OS gauge still shows charge remaining. It is a fuel gauge calibration lag, not a faulty battery. Run one full discharge-charge cycle with all background sync and mobile data active so the gauge IC sees the actual voltage sag profile of the new cell. After calibration, the reported percentage and the real cutoff point align — target a resting voltage of around 3.7V at the 30% mark.

Compatible Models

T618 T628 T700 T718

Technical Specifications

Voltage3.7V
Amp Hours900mAh
Capacity900mAh
Rate3.33Wh
Net Weight17g /0.60 oz
Gross Weight42g /1.48 oz
Approximate Weight42g /1.48 oz
Dimension 53.00 x 34.00 x 4.80mm

Product Highlights

  • Brand: KDDI
  • 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 cuts off without warning at around 25% — is the replacement battery faulty?

It is not faulty. The fuel gauge IC is still using the discharge curve it learned from the old, degraded cell, so the percentage on screen does not match the new cell's actual voltage behaviour. Under modem or screen load the voltage dips fast enough to hit the BMS cutoff before the OS registers it. Run one full uninterrupted discharge to auto-off, then charge straight to 100% — after that single cycle the gauge recalibrates and the cutoffs line up.

Fast charging stopped working after I swapped in the replacement battery — it only charges slowly now.

On the first cycle after installation, many proprietary charge protocols are not accepted by the new BMS until it completes one standard charge handshake. The phone defaults to slow 5V charging as a fallback. Complete one full charge at the slow rate, then reconnect with the original fast-charge cable and adapter — the protocol negotiation should succeed on the second connection. If fast charging still does not engage, check that the USB port and cable are carrying the correct voltage by testing with a USB meter; the adapter should output above 7V for fast-charge mode to trigger.

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

If the cell discharged below approximately 2.5V during storage, the BMS enters a lockout state and blocks current flow to protect the cell. The phone will show nothing — no charging indicator, no boot. Connect it to a low-current 5V USB source (a standard wall adapter, not a fast charger) and leave it for 20–30 minutes without pressing anything. The BMS pre-charge circuit will trickle current into the cell until it crosses the recovery threshold, at which point normal charging resumes and the phone will boot.

Payment & Security

Payment methods

  • American Express
  • Apple Pay
  • Diners Club
  • Discover
  • Google Pay
  • Mastercard
  • PayPal
  • Shop Pay
  • Visa

Your payment information is processed securely. We do not store credit card details nor have access to your credit card information.

Related Products

Explay Ice Replacement Battery, 3.7V, 900mAh, Li-ion 1

Engineered for Performance. Built to Last.

Check out our top-rated selection of reliable products built to last. We offer high-quality options that deliver consistent performance for all your needs.

Our Collections