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

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

Asus Eee Transformer TF101 Compatible Battery 7.4V 3300mAh

Up to 19% off
New arrival
From $46.99 USD $57.99
Shipping calculated at checkout.
Fits Asus Eee Transformer TF101 and TF101-X1; replaces C21-EP101, C21EP101, C22-EP101.
7.4V, 3300mAh lithium-polymer delivers 24.42Wh — sufficient for full-day tablet use without dock.
Connector seats into the tablet's battery slot with mechanical locking tab; orientation marked inside housing.
We ran full discharge and recharge cycles; BMS accepted negotiation without fault codes or thermal spikes.
After installation, run one full discharge to automatic shutoff then charge uninterrupted to 100% — this resets the fuel gauge IC calibration against the new cell and resolves the inaccurate percentage display that appears after a swap.
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

7.4V

Amp

3300mAh

Asus Eee Transformer TF101 — 7.4V Li-Polymer Replacement Battery (C21-EP101)

This is a 7.4V, 3300mAh Li-Polymer battery for the Asus Eee Transformer TF101 and Eee Pad Transformer TF101 series tablets. It replaces OEM part numbers C21-EP101, C21EP101, and C22-EP101. The battery powers the tablet unit independently from the keyboard dock.

  • TF101 and Eee Pad Transformer TF101 series compatibility: These models share the same 7.4V battery rail, connector pinout, and BMS handshake protocol across the TF101-X1 and other variants in the lineup, so one cell fits the full range.
  • Bench tested on actual hardware: We cycled this battery through charge and discharge on TF101 hardware. The BMS accepted the charge cycle without fault flags and reported state-of-charge accurately after one full recalibration pass.
  • Fuel gauge recalibration after swap: After fitting this battery, run the tablet down to automatic shutoff, then charge uninterrupted to 100% without unplugging. The TF101 fuel gauge IC calibrates against the new cell during that single cycle, which clears the inaccurate percentage readings that appear immediately after a swap.

TF101 shutting down at 15–25% remaining

The TF101 draws simultaneous load from the display backlight and WiFi radio, which creates a combined current spike that the aged fuel gauge misreads as a voltage cliff. The BMS triggers a protection cutoff before the cell is actually depleted. This happens most often when brightness is high and the device is actively syncing. Run one full discharge-to-shutoff cycle to give the fuel gauge IC accurate endpoint data, and the early shutoffs typically stop.

Fast charging unavailable after battery replacement

The TF101 uses a proprietary charge negotiation sequence between the charge IC and the battery BMS. On a fresh cell, that handshake needs one accepted charge cycle before the device will authorise higher charge current. Plugging in immediately after installation and seeing only trickle charge is normal. Let the first charge complete fully to 100% uninterrupted — the higher charge rate becomes available from the second cycle onward.

Compatible Models

Eee Transformer TF101 Eee Pad Transformer TR101 prefix Eee Pad Transformer TF101 prefix Mobile Docking Eee Pad Transformer TF101 TF101-X1 16GB Eee Pad Transformer TF101X1 16GB Eee Pad Transformer TF101-1B001A Eee Pad Transformer TF1011B001A Eee Pad Transformer TF101-1B002A Eee Pad Transformer TF1011B002A Eee Pad Transformer TF101-1B003A Eee Pad Transformer TF1011B003A Eee Pad Transformer TF101-1B004A Eee Pad Transformer TF1011B004A Eee Pad Transformer TF101-1B006A Eee Pad Transformer TF1011B006A Eee Pad Transformer TF101-1B011A Eee Pad Transformer TF1011B011A Eee Pad Transformer TF101-1B012A Eee Pad Transformer TF1011B012A Eee Pad Transformer TF101-1B017A Eee Pad Transformer TF1011B017A Eee Pad Transformer TF101-1B023A Eee Pad Transformer TF1011B023A Eee Pad Transformer TF101-1B025A Eee Pad Transformer TF1011B025A Eee Pad Transformer TF101-1B026A Eee Pad Transformer TF1011B026A Eee Pad Transformer TF101-1B027A Eee Pad Transformer TF1011B027A Eee Pad Transformer TF101-1B028A Eee Pad Transformer TF1011B028A Eee Pad Transformer TF101-1b029A Eee Pad Transformer TF1011b029A Eee Pad Transformer TF101-1B030A Eee Pad Transformer TF1011B030A Eee Pad Transformer TF101-1B031A Eee Pad Transformer TF1011B031A Eee Pad Transformer TF101-1B033A Eee Pad Transformer TF1011B033A Eee Pad Transformer TF101-1B046A Eee Pad Transformer TF1011B046A Eee Pad Transformer TF101-1B047A Eee Pad Transformer TF1011B047A Eee Pad Transformer TF101-1B048A Eee Pad Transformer TF1011B048A Eee Pad Transformer TF101-1B050A Eee Pad Transformer TF1011B050A Eee Pad Transformer TF101-1B090A Eee Pad Transformer TF1011B090A Eee Pad Transformer TF101-1B097A Eee Pad Transformer TF1011B097A Eee Pad Transformer TF101-1B100A Eee Pad Transformer TF1011B100A Eee Pad Transformer TF101-1B118A Eee Pad Transformer TF1011B118A Eee Pad Transformer TF101-1B135A Eee Pad Transformer TF1011B135A Eee Pad Transformer TF101-1B141A Eee Pad Transformer TF1011B141A Eee Pad Transformer TF101-1B179A Eee Pad Transformer TF1011B179A Eee Pad Transformer TF101-1B180A Eee Pad Transformer TF1011B180A Eee Pad Transformer TF101-1B185A Eee Pad Transformer TF1011B185A Eee Pad Transformer TF101-1B186A Eee Pad Transformer TF1011B186A Eee Pad Transformer TF101-1B221A Eee Pad Transformer TF1011B221A Eee Pad Transformer TF101G-1B034A Eee Pad Transformer TF101G1B034A Eee Pad Transformer TF101G-1B047A Eee Pad Transformer TF101G1B047A Eee Pad Transformer TF101G-1B046A Eee Pad Transformer TF101G1B046A Eee Pad Transformer TF101G-1B048A Eee Pad Transformer TF101G1B048A Eee Pad Transformer TF101G-1B050A Eee Pad Transformer TF101G1B050A Eee Pad Transformer TF101G-1B060A Eee Pad Transformer TF101G1B060A Eee Pad Transformer TF101G-1B115A Eee Pad Transformer TF101G1B115A Eee Pad Transformer TF101-B1 Eee Pad Transformer TF101B1 Eee Pad Transformer TF101-X1 Eee Pad Transformer TF101X1 Transformer TF101-A1 Transformer TF101A1 TR101 TF101 Eee Transformer TR101 Eee Pad Transformer TR101 Eee Pad Transformer TF101 Mobile Docking Eee Pad Transformer TF101

Replaces Part Numbers

C21-EP101 C21EP101 C22-EP101

Technical Specifications

Voltage7.4V
Amp Hours3300mAh
Capacity3300mAh
Rate24.42Wh
Net Weight128g /4.52 oz
Gross Weight268g /9.45 oz
Approximate Weight268g /9.45 oz
Dimension 136.93 x 102.58 x 4.22mm

Product Highlights

  • Brand: Asus
  • 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 TF101 shows 40% battery but shuts down immediately — why does this happen after fitting a new battery?

The fuel gauge IC on the TF101 is calibrated to the discharge curve of the old cell. When a new cell is fitted, the IC's stored endpoint data no longer matches actual cell voltage, so it calls a low-voltage cutoff at the wrong point. Run the tablet down to automatic shutoff, then charge uninterrupted to 100%. After that single full cycle the fuel gauge recalibrates against the new cell and the premature shutoffs stop.

The TF101 percentage is jumping around — it dropped from 60% to 20% in a few minutes then jumped back up.

Erratic percentage jumps on a new cell are a fuel gauge drift problem, not a faulty battery. The TF101's charge tracking IC loses accuracy when the reference curve it stored no longer matches the new cell's impedance profile. One full discharge to automatic shutoff followed by a complete uninterrupted charge to 100% resets the reference. After that cycle, the reported percentage should track steadily without large jumps.

After swapping the battery, the TF101 charges slowly even with the original charger — is the charge IC limiting current on the new cell?

Yes. On the first cycle after a swap, the TF101 charge IC defaults to a conservative current limit until it completes one full accepted charge handshake with the new BMS. This is a built-in protection behaviour, not a fault. Let the first charge run completely to 100% without disconnecting. On the second and subsequent charges the IC negotiates normal current and the slow-fill behaviour goes away.

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

Asus Eee Transformer TF101 Replacement Battery, 7.4V, 3300mAh, Li-Polymer 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