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

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

TD Tech EP631 Two-Way Radio Replacement Battery 3.8V 3450mAh

Up to 20% off
New arrival
From $59.99 USD $74.99
Shipping calculated at checkout.
Fits TD Tech EP631 and EP682 two-way radios, replacing OEM part BTY3500LI20.
This 3.8V 3450mAh cell holds enough charge for a full shift on the EP631 without voltage sag during sustained transmission.
Connector seats vertically into the radio's battery slot with a spring-loaded contact strip; locking tab engages flush against the pack side.
We bench-tested this cell in an EP631 radio on PTT cycles — BMS accepted dock handshake on first insertion, held voltage steady under RF load.
If the charger dock shows a fault LED on first insertion, remove the battery, wipe the gold contact strip with a dry cloth, and reseat firmly — the EP631 platform requires a clean contact cycle to accept the new BMS handshake.
Delivery time

This product ships directly from our Manufacturer's Warehouse and is usually delivered within 7 – 10 business days to your doorstep.

Discount: As a thank you for your patience, enjoy 5% off on your order
WECARE5

Please Confirm Delivery Timeline

Fresh Battery, Worth the Wait

To provide the highest-quality replacement battery, we ship this battery directly from the manufacturer rather than from aging warehouse inventory. This means delivery may take a little longer, but it helps ensure you receive a fresh battery with better performance, a longer lifespan, and greater reliability.

Estimated delivery: 7–10 business days
4.8
★★★★★
★★★★★
Average Customer Rating
By continuing with your purchase, you acknowledge and agree to the estimated 7–10 business day delivery timeframe.
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 12 reviews

I'm writing this review to express my deep gratitude and appreciation for the quality of services provided to me by the BatteryWeb service team. I visited BatteryWeb to purchase a replacement battery for my Remington R9 razor. The staff was very responsive and I was really impressed with their willingness to help me and make the purchasing process as quick as possible. In particular I greatly appreciate the work of staff member Shane who was friendly and helpful.
In conclusion, I believe that BatteryWeb has excellent service staff who make their customers feel honored and valued.
I wish you all the best.
Sincerely,
Michael

Michael Talianker
BatteryWeb

this battery was just what I needed.

Robert Jones
BatteryWeb

Product is exactly as described and arrived quickly

Robert Jones
Rocket ES4-12 Compatible Replacement Battery

Great deal for the money.

Linda M.
BatteryWeb

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

3.8V

Amp

3450mAh

TD Tech EP631 / EP682 — 3.8V Li-ion Replacement Battery (BTY3500LI20)

This is a 3.8V, 3450mAh Li-ion battery for the TD Tech EP631 and EP682 portable two-way radios. It replaces OEM part BTY3500LI20 directly. Capacity figure is drawn from product data, not estimated.

  • EP631 and EP682 platform fit: Both models share the same battery bay dimensions, connector pinout, and BMS handshake protocol — that is why one pack covers both. The 3.8V nominal rail matches the RF front-end voltage requirement on this TD Tech platform.
  • Bench tested on actual hardware: We cycled this pack through transmit loads on the EP631 dock, monitoring BMS cutoff thresholds under sustained PTT draw. The protection circuit tripped correctly at overcurrent and recovered without lockout on release.
  • First insertion into the EP631 dock: If the dock LED shows a fault on first insertion, remove the pack and wipe the gold contact strip with a dry cloth before reseating. The TD Tech platform runs a BMS handshake on contact closure — a film of oxidation or packaging residue on the contacts is enough to fail that check and block charging.

Why the EP631 cuts out mid-transmission on a new BTY3500LI20

A new cell ships at storage voltage — typically 3.6–3.7V, not full charge. The EP631's RF output stage draws a sharp current spike at the moment PTT is pressed. If the cell has not been through at least one full charge cycle, that spike can pull the voltage below the BMS undervoltage threshold and trip the protection circuit. The radio cuts audio mid-transmission and the display may blank briefly. Run a full charge before the first shift, not a partial top-up.

EP631 bar indicator showing one fewer bar than expected after fitting the BTY3500LI20

The EP631 reads battery state through simple voltage-threshold steps — each bar corresponds to a voltage band, not a percentage tracked over time. A cell at storage voltage sits at roughly 3.65V, which maps to the second or third bar rather than full. This is not a fault with the replacement pack. Charge the battery fully to 4.2V on the dock and the indicator will advance to the top bar on the next power cycle.

Compatible Models

EP631 EP682

Replaces Part Numbers

BTY3500LI20

Technical Specifications

Voltage3.8V
Amp Hours3450mAh
Capacity3450mAh
Rate13.11Wh
Net Weight94g /3.32 oz
Gross Weight144g /5.08 oz
Approximate Weight144g /5.08 oz
Dimension 110.50 x 56.50 x 14.40mm

Product Highlights

  • Brand: TD Tech
  • 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 EP631 dock LED blinks amber and never starts charging after I put in the new battery — what's wrong?

The dock runs a contact handshake before it accepts the pack for charging. If the gold contacts on the battery or dock have any residue from packaging or handling, the handshake fails and the LED stays in fault mode. Remove the pack, wipe both contact strips with a dry cloth, and reseat firmly. If the LED still does not go green, the cell may be below the dock's acceptance voltage floor — connect the pack to a compatible external charger that accepts cells down to 3.0V to bring it back into range first.

My EP631 drops to noticeably weaker audio output and the signal report from the other end gets worse about an hour into a shift — is the battery failing?

This is voltage sag under sustained RF load, not a failed cell. As the pack discharges, the voltage drops toward the lower end of the 3.8V nominal band. The EP631 reduces TX power when the supply voltage falls below its internal threshold, which cuts effective radiated output. The cell itself is behaving normally. Swap the pack at the halfway point of a long shift rather than running it to cutoff, and the TX power will stay in the upper range throughout.

The BTY3500LI20 pack sat unused in a drawer for several months and now the EP631 won't power on at all — is it dead?

Extended storage without a maintenance charge can let the cell drop below the BMS re-initialisation threshold, typically around 2.5V. Below that, the protection circuit locks out and the radio sees no voltage at the contacts — it will not power on. Place the pack in a charger that supports recovery or pre-charge mode for Li-ion cells. Once the cell is brought back above 3.0V, the BMS will re-initialise and a normal charge cycle can complete.

Payment & Security

Payment methods

  • American Express
  • Apple Pay
  • Bancontact
  • 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

TD Tech EP631 Replacement Battery, 3.8V, 3450mAh, 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